# GstBaseTransform

This base class is for filter elements that process data. Elements that are suitable for implementation using GstBaseTransform are ones where the size and caps of the output is known entirely from the input caps and buffer sizes. These include elements that directly transform one buffer into another, modify the contents of a buffer in-place, as well as elements that collate multiple input buffers into one output buffer, or that expand one input buffer into multiple output buffers. See below for more concrete use cases.

It provides for:

- one sinkpad and one srcpad

- Possible formats on sink and source pad implemented with custom transform_caps function. By default uses same format on sink and source.

- Handles state changes

- Does flushing

- Push mode

- Pull mode if the sub-class transform can operate on arbitrary data

# Use Cases

## Passthrough mode

- Element has no interest in modifying the buffer. It may want to inspect it, in which case the element should have a transform_ip function. If there is no transform_ip function in passthrough mode, the buffer is pushed intact.

- The passthrough_on_same_caps variable will automatically set/unset passthrough based on whether the element negotiates the same caps on both pads.

- passthrough_on_same_caps on an element that doesn't implement a transform_caps function is useful for elements that only inspect data (such as level)

- Example elements

  - Level
  - Videoscale, audioconvert, videoconvert, audioresample in certain modes.

## Modifications in-place - input buffer and output buffer are the same thing.

- The element must implement a transform_ip function.

- Output buffer size must <= input buffer size

- If the always_in_place flag is set, non-writable buffers will be copied and passed to the transform_ip function, otherwise a new buffer will be created and the transform function called.

- Incoming writable buffers will be passed to the transform_ip function immediately.

- only implementing transform_ip and not transform implies always_in_place = TRUE

  - Example elements:
    - Volume
    - Audioconvert in certain modes (signed/unsigned conversion)
    - videoconvert in certain modes (endianness swapping)

## Modifications only to the caps/metadata of a buffer

- The element does not require writable data, but non-writable buffers should be subbuffered so that the meta-information can be replaced.

- Elements wishing to operate in this mode should replace the prepare_output_buffer method to create subbuffers of the input buffer and set always_in_place to TRUE

- Example elements

  - Capsfilter when setting caps on outgoing buffers that have none.
  - identity when it is going to re-timestamp buffers by datarate.

## Normal mode

- always_in_place flag is not set, or there is no transform_ip function
- Element will receive an input buffer and output buffer to operate on.
- Output buffer is allocated by calling the prepare_output_buffer function.
- Example elements:
  - Videoscale, videoconvert, audioconvert when doing scaling/conversions

## Special output buffer allocations

- Elements which need to do special allocation of their output buffers beyond allocating output buffers via the negotiated allocator or buffer pool should implement the prepare_output_buffer method.

- Example elements:

  - efence

# Sub-class settable flags on GstBaseTransform

- passthrough

  - Implies that in the current configuration, the sub-class is not interested in modifying the buffers.
  - Elements which are always in passthrough mode whenever the same caps has been negotiated on both pads can set the class variable passthrough_on_same_caps to have this behaviour automatically.

- always_in_place

  - Determines whether a non-writable buffer will be copied before passing to the transform_ip function.

  - Implied TRUE if no transform function is implemented.

  - Implied FALSE if ONLY transform function is implemented.

## GstBaseTransform

    GObject
        ╰──GInitiallyUnowned
            ╰──GstObject
                ╰──GstElement
                    ╰──GstBaseTransform

The opaque GstBaseTransform data structure.

### Members

`element` (GstElement) –
No description available
`sinkpad` (GstPad *) –
No description available
`srcpad` (GstPad *) –
No description available
`have_segment` (gboolean) –
No description available
`segment` (GstSegment) –
No description available
`queued_buf` (GstBuffer *) –
No description available

### Class structure

#### GstBaseTransformClass

Subclasses can override any of the available virtual methods or not, as needed. At minimum either transform or transform_ip need to be overridden. If the element can overwrite the input data with the results (data is of the same type and quantity) it should provide transform_ip.

##### Fields

`parent_class` (GstElementClass) –

Element parent class

`passthrough_on_same_caps` (gboolean) –

If set to TRUE, passthrough mode will be automatically enabled if the caps are the same. Set to FALSE by default.

`transform_ip_on_passthrough` (gboolean) –

If set to TRUE, transform_ip will be called in passthrough mode. The passed buffer might not be writable. When FALSE, neither transform nor transform_ip will be called in passthrough mode. Set to TRUE by default.

### GstBase.BaseTransformClass

Subclasses can override any of the available virtual methods or not, as needed. At minimum either transform or transform_ip need to be overridden. If the element can overwrite the input data with the results (data is of the same type and quantity) it should provide transform_ip.

##### Attributes

`parent_class` (Gst.ElementClass) –

Element parent class

`passthrough_on_same_caps` (Number) –

If set to TRUE, passthrough mode will be automatically enabled if the caps are the same. Set to FALSE by default.

`transform_ip_on_passthrough` (Number) –

If set to TRUE, transform_ip will be called in passthrough mode. The passed buffer might not be writable. When FALSE, neither transform nor transform_ip will be called in passthrough mode. Set to TRUE by default.

### GstBase.BaseTransformClass

Subclasses can override any of the available virtual methods or not, as needed. At minimum either transform or transform_ip need to be overridden. If the element can overwrite the input data with the results (data is of the same type and quantity) it should provide transform_ip.

##### Attributes

`parent_class` (Gst.ElementClass) –

Element parent class

`passthrough_on_same_caps` (bool) –

If set to TRUE, passthrough mode will be automatically enabled if the caps are the same. Set to FALSE by default.

`transform_ip_on_passthrough` (bool) –

If set to TRUE, transform_ip will be called in passthrough mode. The passed buffer might not be writable. When FALSE, neither transform nor transform_ip will be called in passthrough mode. Set to TRUE by default.

## GstBase.BaseTransform

    GObject.Object
        ╰──GObject.InitiallyUnowned
            ╰──Gst.Object
                ╰──Gst.Element
                    ╰──GstBase.BaseTransform

The opaque GstBase.BaseTransform data structure.

### Members

`element` (Gst.Element) –
No description available
`sinkpad` (Gst.Pad) –
No description available
`srcpad` (Gst.Pad) –
No description available
`have_segment` (Number) –
No description available
`segment` (Gst.Segment) –
No description available
`queued_buf` (Gst.Buffer) –
No description available

## GstBase.BaseTransform

    GObject.Object
        ╰──GObject.InitiallyUnowned
            ╰──Gst.Object
                ╰──Gst.Element
                    ╰──GstBase.BaseTransform

The opaque GstBase.BaseTransform data structure.

### Members

`element` (Gst.Element) –
No description available
`sinkpad` (Gst.Pad) –
No description available
`srcpad` (Gst.Pad) –
No description available
`have_segment` (bool) –
No description available
`segment` (Gst.Segment) –
No description available
`queued_buf` (Gst.Buffer) –
No description available

### Methods

#### gst_base_transform_get_allocator

    gst_base_transform_get_allocator (GstBaseTransform * trans,
                                      GstAllocator ** allocator,
                                      GstAllocationParams * params)

Lets GstBaseTransform sub-classes know the memory allocator used by the base class and its params.

Unref the allocator after use.

Parameters:

`trans` –

a GstBaseTransform

`allocator` ( [out][optional][nullable][transfer: full]) –

the GstAllocator used

`params` ( [out][optional]) –

the GstAllocationParams of allocator

#### GstBase.BaseTransform.prototype.get_allocator

    function GstBase.BaseTransform.prototype.get_allocator(): {
        // javascript wrapper for 'gst_base_transform_get_allocator'
    }

Lets GstBase.BaseTransform sub-classes know the memory allocator used by the base class and its params.

Unref the allocator after use.

Parameters:

`trans` (GstBase.BaseTransform) –

a GstBase.BaseTransform

#### GstBase.BaseTransform.get_allocator

    def GstBase.BaseTransform.get_allocator (self):
        #python wrapper for 'gst_base_transform_get_allocator'

Lets GstBase.BaseTransform sub-classes know the memory allocator used by the base class and its params.

Unref the allocator after use.

Parameters:

`trans` (GstBase.BaseTransform) –

a GstBase.BaseTransform

#### gst_base_transform_get_buffer_pool

    GstBufferPool *
    gst_base_transform_get_buffer_pool (GstBaseTransform * trans)

Parameters:

`trans` –

a GstBaseTransform

Returns ( [nullable][transfer: full]) –

the instance of the GstBufferPool used by trans; free it after use

#### GstBase.BaseTransform.prototype.get_buffer_pool

    function GstBase.BaseTransform.prototype.get_buffer_pool(): {
        // javascript wrapper for 'gst_base_transform_get_buffer_pool'
    }

Parameters:

`trans` (GstBase.BaseTransform) –

a GstBase.BaseTransform

Returns (Gst.BufferPool) –

the instance of the Gst.BufferPool used by trans; free it after use

#### GstBase.BaseTransform.get_buffer_pool

    def GstBase.BaseTransform.get_buffer_pool (self):
        #python wrapper for 'gst_base_transform_get_buffer_pool'

Parameters:

`trans` (GstBase.BaseTransform) –

a GstBase.BaseTransform

Returns (Gst.BufferPool) –

the instance of the Gst.BufferPool used by trans; free it after use

#### gst_base_transform_is_in_place

    gboolean
    gst_base_transform_is_in_place (GstBaseTransform * trans)

See if trans is configured as a in_place transform.

Parameters:

`trans` –

the GstBaseTransform to query

Returns –

TRUE if the transform is configured in in_place mode.

MT safe.

#### GstBase.BaseTransform.prototype.is_in_place

    function GstBase.BaseTransform.prototype.is_in_place(): {
        // javascript wrapper for 'gst_base_transform_is_in_place'
    }

See if trans is configured as a in_place transform.

Parameters:

`trans` (GstBase.BaseTransform) –

the GstBase.BaseTransform to query

Returns (Number) –

TRUE if the transform is configured in in_place mode.

MT safe.

#### GstBase.BaseTransform.is_in_place

    def GstBase.BaseTransform.is_in_place (self):
        #python wrapper for 'gst_base_transform_is_in_place'

See if trans is configured as a in_place transform.

Parameters:

`trans` (GstBase.BaseTransform) –

the GstBase.BaseTransform to query

Returns (bool) –

TRUE if the transform is configured in in_place mode.

MT safe.

#### gst_base_transform_is_passthrough

    gboolean
    gst_base_transform_is_passthrough (GstBaseTransform * trans)

See if trans is configured as a passthrough transform.

Parameters:

`trans` –

the GstBaseTransform to query

Returns –

TRUE if the transform is configured in passthrough mode.

MT safe.

#### GstBase.BaseTransform.prototype.is_passthrough

    function GstBase.BaseTransform.prototype.is_passthrough(): {
        // javascript wrapper for 'gst_base_transform_is_passthrough'
    }

See if trans is configured as a passthrough transform.

Parameters:

`trans` (GstBase.BaseTransform) –

the GstBase.BaseTransform to query

Returns (Number) –

TRUE if the transform is configured in passthrough mode.

MT safe.

#### GstBase.BaseTransform.is_passthrough

    def GstBase.BaseTransform.is_passthrough (self):
        #python wrapper for 'gst_base_transform_is_passthrough'

See if trans is configured as a passthrough transform.

Parameters:

`trans` (GstBase.BaseTransform) –

the GstBase.BaseTransform to query

Returns (bool) –

TRUE if the transform is configured in passthrough mode.

MT safe.

#### gst_base_transform_is_qos_enabled

    gboolean
    gst_base_transform_is_qos_enabled (GstBaseTransform * trans)

Queries if the transform will handle QoS.

Parameters:

`trans` –

a GstBaseTransform

Returns –

TRUE if QoS is enabled.

MT safe.

#### GstBase.BaseTransform.prototype.is_qos_enabled

    function GstBase.BaseTransform.prototype.is_qos_enabled(): {
        // javascript wrapper for 'gst_base_transform_is_qos_enabled'
    }

Queries if the transform will handle QoS.

Parameters:

`trans` (GstBase.BaseTransform) –

a GstBase.BaseTransform

Returns (Number) –

TRUE if QoS is enabled.

MT safe.

#### GstBase.BaseTransform.is_qos_enabled

    def GstBase.BaseTransform.is_qos_enabled (self):
        #python wrapper for 'gst_base_transform_is_qos_enabled'

Queries if the transform will handle QoS.

Parameters:

`trans` (GstBase.BaseTransform) –

a GstBase.BaseTransform

Returns (bool) –

TRUE if QoS is enabled.

MT safe.

#### gst_base_transform_reconfigure

    gboolean
    gst_base_transform_reconfigure (GstBaseTransform * trans)

Negotiates src pad caps with downstream elements if the source pad is marked as needing reconfiguring. Unmarks GST_PAD_FLAG_NEED_RECONFIGURE in any case. But marks it again if negotiation fails.

Do not call this in the transform or transform_ip vmethod. Call this in submit_input_buffer, prepare_output_buffer or in generate_output before any output buffer is allocated.

It will be default be called when handling an ALLOCATION query or at the very beginning of the default submit_input_buffer implementation.

Parameters:

`trans` –

the GstBaseTransform to set

Returns –

TRUE if the negotiation succeeded, else FALSE.

Since : 1.18

#### GstBase.BaseTransform.prototype.reconfigure

    function GstBase.BaseTransform.prototype.reconfigure(): {
        // javascript wrapper for 'gst_base_transform_reconfigure'
    }

Negotiates src pad caps with downstream elements if the source pad is marked as needing reconfiguring. Unmarks GST_PAD_FLAG_NEED_RECONFIGURE in any case. But marks it again if negotiation fails.

Do not call this in the vfunc_transform or vfunc_transform_ip vmethod. Call this in vfunc_submit_input_buffer, vfunc_prepare_output_buffer or in vfunc_generate_output before any output buffer is allocated.

It will be default be called when handling an ALLOCATION query or at the very beginning of the default vfunc_submit_input_buffer implementation.

Parameters:

`trans` (GstBase.BaseTransform) –

the GstBase.BaseTransform to set

Returns (Number) –

TRUE if the negotiation succeeded, else FALSE.

Since : 1.18

#### GstBase.BaseTransform.reconfigure

    def GstBase.BaseTransform.reconfigure (self):
        #python wrapper for 'gst_base_transform_reconfigure'

Negotiates src pad caps with downstream elements if the source pad is marked as needing reconfiguring. Unmarks GST_PAD_FLAG_NEED_RECONFIGURE in any case. But marks it again if negotiation fails.

Do not call this in the do_transform or do_transform_ip vmethod. Call this in do_submit_input_buffer, do_prepare_output_buffer or in do_generate_output before any output buffer is allocated.

It will be default be called when handling an ALLOCATION query or at the very beginning of the default do_submit_input_buffer implementation.

Parameters:

`trans` (GstBase.BaseTransform) –

the GstBase.BaseTransform to set

Returns (bool) –

TRUE if the negotiation succeeded, else FALSE.

Since : 1.18

#### gst_base_transform_reconfigure_sink

    gst_base_transform_reconfigure_sink (GstBaseTransform * trans)

Instructs trans to request renegotiation upstream. This function is typically called after properties on the transform were set that influence the input format.

Parameters:

`trans` –

a GstBaseTransform

#### GstBase.BaseTransform.prototype.reconfigure_sink

    function GstBase.BaseTransform.prototype.reconfigure_sink(): {
        // javascript wrapper for 'gst_base_transform_reconfigure_sink'
    }

Instructs trans to request renegotiation upstream. This function is typically called after properties on the transform were set that influence the input format.

Parameters:

`trans` (GstBase.BaseTransform) –

a GstBase.BaseTransform

#### GstBase.BaseTransform.reconfigure_sink

    def GstBase.BaseTransform.reconfigure_sink (self):
        #python wrapper for 'gst_base_transform_reconfigure_sink'

Instructs trans to request renegotiation upstream. This function is typically called after properties on the transform were set that influence the input format.

Parameters:

`trans` (GstBase.BaseTransform) –

a GstBase.BaseTransform

#### gst_base_transform_reconfigure_src

    gst_base_transform_reconfigure_src (GstBaseTransform * trans)

Instructs trans to renegotiate a new downstream transform on the next buffer. This function is typically called after properties on the transform were set that influence the output format.

Parameters:

`trans` –

a GstBaseTransform

#### GstBase.BaseTransform.prototype.reconfigure_src

    function GstBase.BaseTransform.prototype.reconfigure_src(): {
        // javascript wrapper for 'gst_base_transform_reconfigure_src'
    }

Instructs trans to renegotiate a new downstream transform on the next buffer. This function is typically called after properties on the transform were set that influence the output format.

Parameters:

`trans` (GstBase.BaseTransform) –

a GstBase.BaseTransform

#### GstBase.BaseTransform.reconfigure_src

    def GstBase.BaseTransform.reconfigure_src (self):
        #python wrapper for 'gst_base_transform_reconfigure_src'

Instructs trans to renegotiate a new downstream transform on the next buffer. This function is typically called after properties on the transform were set that influence the output format.

Parameters:

`trans` (GstBase.BaseTransform) –

a GstBase.BaseTransform

#### gst_base_transform_set_gap_aware

    gst_base_transform_set_gap_aware (GstBaseTransform * trans,
                                      gboolean gap_aware)

If gap_aware is FALSE (the default), output buffers will have the GST_BUFFER_FLAG_GAP flag unset.

If set to TRUE, the element must handle output buffers with this flag set correctly, i.e. it can assume that the buffer contains neutral data but must unset the flag if the output is no neutral data.

MT safe.

Parameters:

`trans` –

a GstBaseTransform

`gap_aware` –

New state

#### GstBase.BaseTransform.prototype.set_gap_aware

    function GstBase.BaseTransform.prototype.set_gap_aware(gap_aware: Number): {
        // javascript wrapper for 'gst_base_transform_set_gap_aware'
    }

If gap_aware is FALSE (the default), output buffers will have the Gst.BufferFlags.GAP flag unset.

If set to TRUE, the element must handle output buffers with this flag set correctly, i.e. it can assume that the buffer contains neutral data but must unset the flag if the output is no neutral data.

MT safe.

Parameters:

`trans` (GstBase.BaseTransform) –

a GstBase.BaseTransform

`gap_aware` (Number) –

New state

#### GstBase.BaseTransform.set_gap_aware

    def GstBase.BaseTransform.set_gap_aware (self, gap_aware):
        #python wrapper for 'gst_base_transform_set_gap_aware'

If gap_aware is FALSE (the default), output buffers will have the Gst.BufferFlags.GAP flag unset.

If set to TRUE, the element must handle output buffers with this flag set correctly, i.e. it can assume that the buffer contains neutral data but must unset the flag if the output is no neutral data.

MT safe.

Parameters:

`trans` (GstBase.BaseTransform) –

a GstBase.BaseTransform

`gap_aware` (bool) –

New state

#### gst_base_transform_set_in_place

    gst_base_transform_set_in_place (GstBaseTransform * trans,
                                     gboolean in_place)

Determines whether a non-writable buffer will be copied before passing to the transform_ip function.

- Always TRUE if no transform function is implemented.
- Always FALSE if ONLY transform function is implemented.

MT safe.

Parameters:

`trans` –

the GstBaseTransform to modify

`in_place` –

Boolean value indicating that we would like to operate on in_place buffers.

#### GstBase.BaseTransform.prototype.set_in_place

    function GstBase.BaseTransform.prototype.set_in_place(in_place: Number): {
        // javascript wrapper for 'gst_base_transform_set_in_place'
    }

Determines whether a non-writable buffer will be copied before passing to the transform_ip function.

- Always TRUE if no transform function is implemented.
- Always FALSE if ONLY transform function is implemented.

MT safe.

Parameters:

`trans` (GstBase.BaseTransform) –

the GstBase.BaseTransform to modify

`in_place` (Number) –

Boolean value indicating that we would like to operate on in_place buffers.

#### GstBase.BaseTransform.set_in_place

    def GstBase.BaseTransform.set_in_place (self, in_place):
        #python wrapper for 'gst_base_transform_set_in_place'

Determines whether a non-writable buffer will be copied before passing to the transform_ip function.

- Always TRUE if no transform function is implemented.
- Always FALSE if ONLY transform function is implemented.

MT safe.

Parameters:

`trans` (GstBase.BaseTransform) –

the GstBase.BaseTransform to modify

`in_place` (bool) –

Boolean value indicating that we would like to operate on in_place buffers.

#### gst_base_transform_set_passthrough

    gst_base_transform_set_passthrough (GstBaseTransform * trans,
                                        gboolean passthrough)

Set passthrough mode for this filter by default. This is mostly useful for filters that do not care about negotiation.

Always TRUE for filters which don't implement either a transform or transform_ip or generate_output method.

MT safe.

Parameters:

`trans` –

the GstBaseTransform to set

`passthrough` –

boolean indicating passthrough mode.

#### GstBase.BaseTransform.prototype.set_passthrough

    function GstBase.BaseTransform.prototype.set_passthrough(passthrough: Number): {
        // javascript wrapper for 'gst_base_transform_set_passthrough'
    }

Set passthrough mode for this filter by default. This is mostly useful for filters that do not care about negotiation.

Always TRUE for filters which don't implement either a transform or transform_ip or generate_output method.

MT safe.

Parameters:

`trans` (GstBase.BaseTransform) –

the GstBase.BaseTransform to set

`passthrough` (Number) –

boolean indicating passthrough mode.

#### GstBase.BaseTransform.set_passthrough

    def GstBase.BaseTransform.set_passthrough (self, passthrough):
        #python wrapper for 'gst_base_transform_set_passthrough'

Set passthrough mode for this filter by default. This is mostly useful for filters that do not care about negotiation.

Always TRUE for filters which don't implement either a transform or transform_ip or generate_output method.

MT safe.

Parameters:

`trans` (GstBase.BaseTransform) –

the GstBase.BaseTransform to set

`passthrough` (bool) –

boolean indicating passthrough mode.

#### gst_base_transform_set_prefer_passthrough

    gst_base_transform_set_prefer_passthrough (GstBaseTransform * trans,
                                               gboolean prefer_passthrough)

If prefer_passthrough is TRUE (the default), trans will check and prefer passthrough caps from the list of caps returned by the transform_caps vmethod.

If set to FALSE, the element must order the caps returned from the transform_caps function in such a way that the preferred format is first in the list. This can be interesting for transforms that can do passthrough transforms but prefer to do something else, like a capsfilter.

MT safe.

Parameters:

`trans` –

a GstBaseTransform

`prefer_passthrough` –

New state

Since : 1.0.1

#### GstBase.BaseTransform.prototype.set_prefer_passthrough

    function GstBase.BaseTransform.prototype.set_prefer_passthrough(prefer_passthrough: Number): {
        // javascript wrapper for 'gst_base_transform_set_prefer_passthrough'
    }

If prefer_passthrough is TRUE (the default), trans will check and prefer passthrough caps from the list of caps returned by the transform_caps vmethod.

If set to FALSE, the element must order the caps returned from the transform_caps function in such a way that the preferred format is first in the list. This can be interesting for transforms that can do passthrough transforms but prefer to do something else, like a capsfilter.

MT safe.

Parameters:

`trans` (GstBase.BaseTransform) –

a GstBase.BaseTransform

`prefer_passthrough` (Number) –

New state

Since : 1.0.1

#### GstBase.BaseTransform.set_prefer_passthrough

    def GstBase.BaseTransform.set_prefer_passthrough (self, prefer_passthrough):
        #python wrapper for 'gst_base_transform_set_prefer_passthrough'

If prefer_passthrough is TRUE (the default), trans will check and prefer passthrough caps from the list of caps returned by the transform_caps vmethod.

If set to FALSE, the element must order the caps returned from the transform_caps function in such a way that the preferred format is first in the list. This can be interesting for transforms that can do passthrough transforms but prefer to do something else, like a capsfilter.

MT safe.

Parameters:

`trans` (GstBase.BaseTransform) –

a GstBase.BaseTransform

`prefer_passthrough` (bool) –

New state

Since : 1.0.1

#### gst_base_transform_set_qos_enabled

    gst_base_transform_set_qos_enabled (GstBaseTransform * trans,
                                        gboolean enabled)

Enable or disable QoS handling in the transform.

MT safe.

Parameters:

`trans` –

a GstBaseTransform

`enabled` –

new state

#### GstBase.BaseTransform.prototype.set_qos_enabled

    function GstBase.BaseTransform.prototype.set_qos_enabled(enabled: Number): {
        // javascript wrapper for 'gst_base_transform_set_qos_enabled'
    }

Enable or disable QoS handling in the transform.

MT safe.

Parameters:

`trans` (GstBase.BaseTransform) –

a GstBase.BaseTransform

`enabled` (Number) –

new state

#### GstBase.BaseTransform.set_qos_enabled

    def GstBase.BaseTransform.set_qos_enabled (self, enabled):
        #python wrapper for 'gst_base_transform_set_qos_enabled'

Enable or disable QoS handling in the transform.

MT safe.

Parameters:

`trans` (GstBase.BaseTransform) –

a GstBase.BaseTransform

`enabled` (bool) –

new state

#### gst_base_transform_update_qos

    gst_base_transform_update_qos (GstBaseTransform * trans,
                                   gdouble proportion,
                                   GstClockTimeDiff diff,
                                   GstClockTime timestamp)

Set the QoS parameters in the transform. This function is called internally when a QOS event is received but subclasses can provide custom information when needed.

MT safe.

Parameters:

`trans` –

a GstBaseTransform

`proportion` –

the proportion

`diff` –

the diff against the clock

`timestamp` –

the timestamp of the buffer generating the QoS expressed in running_time.

#### GstBase.BaseTransform.prototype.update_qos

    function GstBase.BaseTransform.prototype.update_qos(proportion: Number, diff: Number, timestamp: Number): {
        // javascript wrapper for 'gst_base_transform_update_qos'
    }

Set the QoS parameters in the transform. This function is called internally when a QOS event is received but subclasses can provide custom information when needed.

MT safe.

Parameters:

`trans` (GstBase.BaseTransform) –

a GstBase.BaseTransform

`proportion` (Number) –

the proportion

`diff` (Number) –

the diff against the clock

`timestamp` (Number) –

the timestamp of the buffer generating the QoS expressed in running_time.

#### GstBase.BaseTransform.update_qos

    def GstBase.BaseTransform.update_qos (self, proportion, diff, timestamp):
        #python wrapper for 'gst_base_transform_update_qos'

Set the QoS parameters in the transform. This function is called internally when a QOS event is received but subclasses can provide custom information when needed.

MT safe.

Parameters:

`trans` (GstBase.BaseTransform) –

a GstBase.BaseTransform

`proportion` (float) –

the proportion

`diff` (int) –

the diff against the clock

`timestamp` (int) –

the timestamp of the buffer generating the QoS expressed in running_time.

#### gst_base_transform_update_src_caps

    gboolean
    gst_base_transform_update_src_caps (GstBaseTransform * trans,
                                        GstCaps * updated_caps)

Updates the srcpad caps and sends the caps downstream. This function can be used by subclasses when they have already negotiated their caps but found a change in them (or computed new information). This way, they can notify downstream about that change without losing any buffer.

Parameters:

`trans` –

a GstBaseTransform

`updated_caps` –

An updated version of the srcpad caps to be pushed downstream

Returns –

TRUE if the caps could be sent downstream FALSE otherwise

Since : 1.6

#### GstBase.BaseTransform.prototype.update_src_caps

    function GstBase.BaseTransform.prototype.update_src_caps(updated_caps: Gst.Caps): {
        // javascript wrapper for 'gst_base_transform_update_src_caps'
    }

Updates the srcpad caps and sends the caps downstream. This function can be used by subclasses when they have already negotiated their caps but found a change in them (or computed new information). This way, they can notify downstream about that change without losing any buffer.

Parameters:

`trans` (GstBase.BaseTransform) –

a GstBase.BaseTransform

`updated_caps` (Gst.Caps) –

An updated version of the srcpad caps to be pushed downstream

Returns (Number) –

TRUE if the caps could be sent downstream FALSE otherwise

Since : 1.6

#### GstBase.BaseTransform.update_src_caps

    def GstBase.BaseTransform.update_src_caps (self, updated_caps):
        #python wrapper for 'gst_base_transform_update_src_caps'

Updates the srcpad caps and sends the caps downstream. This function can be used by subclasses when they have already negotiated their caps but found a change in them (or computed new information). This way, they can notify downstream about that change without losing any buffer.

Parameters:

`trans` (GstBase.BaseTransform) –

a GstBase.BaseTransform

`updated_caps` (Gst.Caps) –

An updated version of the srcpad caps to be pushed downstream

Returns (bool) –

TRUE if the caps could be sent downstream FALSE otherwise

Since : 1.6

### Properties

#### qos

    “qos” gboolean

Flags : Read / Write

#### qos

    “qos” Number

Flags : Read / Write

#### qos

    “self.props.qos” bool

Flags : Read / Write

### Virtual Methods

#### accept_caps

    gboolean
    accept_caps (GstBaseTransform * trans,
                 GstPadDirection direction,
                 GstCaps * caps)

Optional. Subclasses can override this method to check if caps can be handled by the element. The default implementation might not be the most optimal way to check this in all cases.

Parameters:

`trans` –
No description available
`direction` –
No description available
`caps` –
No description available
Returns –
No description available

#### vfunc_accept_caps

    function vfunc_accept_caps(trans: GstBase.BaseTransform, direction: Gst.PadDirection, caps: Gst.Caps): {
        // javascript implementation of the 'accept_caps' virtual method
    }

Optional. Subclasses can override this method to check if caps can be handled by the element. The default implementation might not be the most optimal way to check this in all cases.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`direction` (Gst.PadDirection) –
No description available
`caps` (Gst.Caps) –
No description available
Returns (Number) –
No description available

#### do_accept_caps

    def do_accept_caps (trans, direction, caps):
        #python implementation of the 'accept_caps' virtual method

Optional. Subclasses can override this method to check if caps can be handled by the element. The default implementation might not be the most optimal way to check this in all cases.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`direction` (Gst.PadDirection) –
No description available
`caps` (Gst.Caps) –
No description available
Returns (bool) –
No description available

#### before_transform

    before_transform (GstBaseTransform * trans,
                      GstBuffer * buffer)

Optional. This method is called right before the base class will start processing. Dynamic properties or other delayed configuration could be performed in this method.

Parameters:

`trans` –
No description available
`buffer` –
No description available

#### vfunc_before_transform

    function vfunc_before_transform(trans: GstBase.BaseTransform, buffer: Gst.Buffer): {
        // javascript implementation of the 'before_transform' virtual method
    }

Optional. This method is called right before the base class will start processing. Dynamic properties or other delayed configuration could be performed in this method.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`buffer` (Gst.Buffer) –
No description available

#### do_before_transform

    def do_before_transform (trans, buffer):
        #python implementation of the 'before_transform' virtual method

Optional. This method is called right before the base class will start processing. Dynamic properties or other delayed configuration could be performed in this method.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`buffer` (Gst.Buffer) –
No description available

#### copy_metadata

    gboolean
    copy_metadata (GstBaseTransform * trans,
                   GstBuffer * input,
                   GstBuffer * outbuf)

Optional. Copy the metadata from the input buffer to the output buffer. The default implementation will copy the flags, timestamps and offsets of the buffer.

Parameters:

`trans` –
No description available
`input` –
No description available
`outbuf` –
No description available
Returns –
No description available

#### vfunc_copy_metadata

    function vfunc_copy_metadata(trans: GstBase.BaseTransform, input: Gst.Buffer, outbuf: Gst.Buffer): {
        // javascript implementation of the 'copy_metadata' virtual method
    }

Optional. Copy the metadata from the input buffer to the output buffer. The default implementation will copy the flags, timestamps and offsets of the buffer.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`input` (Gst.Buffer) –
No description available
`outbuf` (Gst.Buffer) –
No description available
Returns (Number) –
No description available

#### do_copy_metadata

    def do_copy_metadata (trans, input, outbuf):
        #python implementation of the 'copy_metadata' virtual method

Optional. Copy the metadata from the input buffer to the output buffer. The default implementation will copy the flags, timestamps and offsets of the buffer.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`input` (Gst.Buffer) –
No description available
`outbuf` (Gst.Buffer) –
No description available
Returns (bool) –
No description available

#### decide_allocation

    gboolean
    decide_allocation (GstBaseTransform * trans,
                       GstQuery * query)

Setup the allocation parameters for allocating output buffers. The passed in query contains the result of the downstream allocation query. This function is only called when not operating in passthrough mode. The default implementation will remove all memory dependent metadata. If there is a filter_meta method implementation, it will be called for all metadata API in the downstream query, otherwise the metadata API is removed.

Parameters:

`trans` –
No description available
`query` –
No description available
Returns –
No description available

#### vfunc_decide_allocation

    function vfunc_decide_allocation(trans: GstBase.BaseTransform, query: Gst.Query): {
        // javascript implementation of the 'decide_allocation' virtual method
    }

Setup the allocation parameters for allocating output buffers. The passed in query contains the result of the downstream allocation query. This function is only called when not operating in passthrough mode. The default implementation will remove all memory dependent metadata. If there is a filter_meta method implementation, it will be called for all metadata API in the downstream query, otherwise the metadata API is removed.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`query` (Gst.Query) –
No description available
Returns (Number) –
No description available

#### do_decide_allocation

    def do_decide_allocation (trans, query):
        #python implementation of the 'decide_allocation' virtual method

Setup the allocation parameters for allocating output buffers. The passed in query contains the result of the downstream allocation query. This function is only called when not operating in passthrough mode. The default implementation will remove all memory dependent metadata. If there is a filter_meta method implementation, it will be called for all metadata API in the downstream query, otherwise the metadata API is removed.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`query` (Gst.Query) –
No description available
Returns (bool) –
No description available

#### filter_meta

    gboolean
    filter_meta (GstBaseTransform * trans,
                 GstQuery * query,
                 GType api,
                 const GstStructure * params)

Return TRUE if the metadata API should be proposed in the upstream allocation query. The default implementation is NULL and will cause all metadata to be removed.

Parameters:

`trans` –
No description available
`query` –
No description available
`api` –
No description available
`params` –
No description available
Returns –
No description available

#### vfunc_filter_meta

    function vfunc_filter_meta(trans: GstBase.BaseTransform, query: Gst.Query, api: GObject.Type, params: Gst.Structure): {
        // javascript implementation of the 'filter_meta' virtual method
    }

Return TRUE if the metadata API should be proposed in the upstream allocation query. The default implementation is NULL and will cause all metadata to be removed.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`query` (Gst.Query) –
No description available
`api` (GObject.Type) –
No description available
`params` (Gst.Structure) –
No description available
Returns (Number) –
No description available

#### do_filter_meta

    def do_filter_meta (trans, query, api, params):
        #python implementation of the 'filter_meta' virtual method

Return TRUE if the metadata API should be proposed in the upstream allocation query. The default implementation is NULL and will cause all metadata to be removed.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`query` (Gst.Query) –
No description available
`api` (GObject.Type) –
No description available
`params` (Gst.Structure) –
No description available
Returns (bool) –
No description available

#### fixate_caps

    GstCaps *
    fixate_caps (GstBaseTransform * trans,
                 GstPadDirection direction,
                 GstCaps * caps,
                 GstCaps * othercaps)

Optional. Given the pad in this direction and the given caps, fixate the caps on the other pad. The function takes ownership of othercaps and returns a fixated version of othercaps. othercaps is not guaranteed to be writable.

Parameters:

`trans` –
No description available
`direction` –
No description available
`caps` –
No description available
`othercaps` –
No description available
Returns –
No description available

#### vfunc_fixate_caps

    function vfunc_fixate_caps(trans: GstBase.BaseTransform, direction: Gst.PadDirection, caps: Gst.Caps, othercaps: Gst.Caps): {
        // javascript implementation of the 'fixate_caps' virtual method
    }

Optional. Given the pad in this direction and the given caps, fixate the caps on the other pad. The function takes ownership of othercaps and returns a fixated version of othercaps. othercaps is not guaranteed to be writable.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`direction` (Gst.PadDirection) –
No description available
`caps` (Gst.Caps) –
No description available
`othercaps` (Gst.Caps) –
No description available
Returns (Gst.Caps) –
No description available

#### do_fixate_caps

    def do_fixate_caps (trans, direction, caps, othercaps):
        #python implementation of the 'fixate_caps' virtual method

Optional. Given the pad in this direction and the given caps, fixate the caps on the other pad. The function takes ownership of othercaps and returns a fixated version of othercaps. othercaps is not guaranteed to be writable.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`direction` (Gst.PadDirection) –
No description available
`caps` (Gst.Caps) –
No description available
`othercaps` (Gst.Caps) –
No description available
Returns (Gst.Caps) –
No description available

#### generate_output

    GstFlowReturn
    generate_output (GstBaseTransform * trans,
                     GstBuffer ** outbuf)

Called after each new input buffer is submitted repeatedly until it either generates an error or fails to generate an output buffer. The default implementation takes the contents of the queued_buf variable, generates an output buffer if needed by calling the class prepare_output_buffer, and then calls either transform or transform_ip. Elements that don't do 1-to-1 transformations of input to output buffers can either return GST_BASE_TRANSFORM_FLOW_DROPPED or simply not generate an output buffer until they are ready to do so. (Since: 1.6)

Parameters:

`trans` –
No description available
`outbuf` –
No description available
Returns –
No description available

#### vfunc_generate_output

    function vfunc_generate_output(trans: GstBase.BaseTransform): {
        // javascript implementation of the 'generate_output' virtual method
    }

Called after each new input buffer is submitted repeatedly until it either generates an error or fails to generate an output buffer. The default implementation takes the contents of the queued_buf variable, generates an output buffer if needed by calling the class prepare_output_buffer, and then calls either transform or transform_ip. Elements that don't do 1-to-1 transformations of input to output buffers can either return GST_BASE_TRANSFORM_FLOW_DROPPED or simply not generate an output buffer until they are ready to do so. (Since: 1.6)

Parameters:

`trans` (GstBase.BaseTransform) –
No description available

Returns a tuple made of:

(Gst.FlowReturn ) –
No description available
`outbuf` (Gst.Buffer ) –
No description available

#### do_generate_output

    def do_generate_output (trans):
        #python implementation of the 'generate_output' virtual method

Called after each new input buffer is submitted repeatedly until it either generates an error or fails to generate an output buffer. The default implementation takes the contents of the queued_buf variable, generates an output buffer if needed by calling the class prepare_output_buffer, and then calls either transform or transform_ip. Elements that don't do 1-to-1 transformations of input to output buffers can either return GST_BASE_TRANSFORM_FLOW_DROPPED or simply not generate an output buffer until they are ready to do so. (Since: 1.6)

Parameters:

`trans` (GstBase.BaseTransform) –
No description available

Returns a tuple made of:

(Gst.FlowReturn ) –
No description available
`outbuf` (Gst.Buffer ) –
No description available

#### get_unit_size

    gboolean
    get_unit_size (GstBaseTransform * trans,
                   GstCaps * caps,
                   gsize* size)

Required if the transform is not in-place. Get the size in bytes of one unit for the given caps.

Parameters:

`trans` –
No description available
`caps` –
No description available
`size` –
No description available
Returns –
No description available

#### vfunc_get_unit_size

    function vfunc_get_unit_size(trans: GstBase.BaseTransform, caps: Gst.Caps): {
        // javascript implementation of the 'get_unit_size' virtual method
    }

Required if the transform is not in-place. Get the size in bytes of one unit for the given caps.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`caps` (Gst.Caps) –
No description available

Returns a tuple made of:

(Number ) –
No description available
`size` (Number ) –
No description available

#### do_get_unit_size

    def do_get_unit_size (trans, caps):
        #python implementation of the 'get_unit_size' virtual method

Required if the transform is not in-place. Get the size in bytes of one unit for the given caps.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`caps` (Gst.Caps) –
No description available

Returns a tuple made of:

(bool ) –
No description available
`size` (int ) –
No description available

#### prepare_output_buffer

    GstFlowReturn
    prepare_output_buffer (GstBaseTransform * trans,
                           GstBuffer * input,
                           GstBuffer ** outbuf)

Optional. Subclasses can override this to do their own allocation of output buffers. Elements that only do analysis can return a subbuffer or even just return a reference to the input buffer (if in passthrough mode). The default implementation will use the negotiated allocator or bufferpool and transform_size to allocate an output buffer or it will return the input buffer in passthrough mode.

Parameters:

`trans` –
No description available
`input` –
No description available
`outbuf` –
No description available
Returns –
No description available

#### vfunc_prepare_output_buffer

    function vfunc_prepare_output_buffer(trans: GstBase.BaseTransform, input: Gst.Buffer): {
        // javascript implementation of the 'prepare_output_buffer' virtual method
    }

Optional. Subclasses can override this to do their own allocation of output buffers. Elements that only do analysis can return a subbuffer or even just return a reference to the input buffer (if in passthrough mode). The default implementation will use the negotiated allocator or bufferpool and transform_size to allocate an output buffer or it will return the input buffer in passthrough mode.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`input` (Gst.Buffer) –
No description available

Returns a tuple made of:

(Gst.FlowReturn ) –
No description available
`outbuf` (Gst.Buffer ) –
No description available

#### do_prepare_output_buffer

    def do_prepare_output_buffer (trans, input):
        #python implementation of the 'prepare_output_buffer' virtual method

Optional. Subclasses can override this to do their own allocation of output buffers. Elements that only do analysis can return a subbuffer or even just return a reference to the input buffer (if in passthrough mode). The default implementation will use the negotiated allocator or bufferpool and transform_size to allocate an output buffer or it will return the input buffer in passthrough mode.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`input` (Gst.Buffer) –
No description available

Returns a tuple made of:

(Gst.FlowReturn ) –
No description available
`outbuf` (Gst.Buffer ) –
No description available

#### propose_allocation

    gboolean
    propose_allocation (GstBaseTransform * trans,
                        GstQuery * decide_query,
                        GstQuery * query)

Propose buffer allocation parameters for upstream elements. This function must be implemented if the element reads or writes the buffer content. The query that was passed to the decide_allocation is passed in this method (or NULL when the element is in passthrough mode). The default implementation will pass the query downstream when in passthrough mode and will copy all the filtered metadata API in non-passthrough mode.

Parameters:

`trans` –
No description available
`decide_query` –
No description available
`query` –
No description available
Returns –
No description available

#### vfunc_propose_allocation

    function vfunc_propose_allocation(trans: GstBase.BaseTransform, decide_query: Gst.Query, query: Gst.Query): {
        // javascript implementation of the 'propose_allocation' virtual method
    }

Propose buffer allocation parameters for upstream elements. This function must be implemented if the element reads or writes the buffer content. The query that was passed to the decide_allocation is passed in this method (or NULL when the element is in passthrough mode). The default implementation will pass the query downstream when in passthrough mode and will copy all the filtered metadata API in non-passthrough mode.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`decide_query` (Gst.Query) –
No description available
`query` (Gst.Query) –
No description available
Returns (Number) –
No description available

#### do_propose_allocation

    def do_propose_allocation (trans, decide_query, query):
        #python implementation of the 'propose_allocation' virtual method

Propose buffer allocation parameters for upstream elements. This function must be implemented if the element reads or writes the buffer content. The query that was passed to the decide_allocation is passed in this method (or NULL when the element is in passthrough mode). The default implementation will pass the query downstream when in passthrough mode and will copy all the filtered metadata API in non-passthrough mode.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`decide_query` (Gst.Query) –
No description available
`query` (Gst.Query) –
No description available
Returns (bool) –
No description available

#### query

    gboolean
    query (GstBaseTransform * trans,
           GstPadDirection direction,
           GstQuery * query)

Optional. Handle a requested query. Subclasses that implement this must chain up to the parent if they didn't handle the query

Parameters:

`trans` –
No description available
`direction` –
No description available
`query` –
No description available
Returns –
No description available

#### vfunc_query

    function vfunc_query(trans: GstBase.BaseTransform, direction: Gst.PadDirection, query: Gst.Query): {
        // javascript implementation of the 'query' virtual method
    }

Optional. Handle a requested query. Subclasses that implement this must chain up to the parent if they didn't handle the query

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`direction` (Gst.PadDirection) –
No description available
`query` (Gst.Query) –
No description available
Returns (Number) –
No description available

#### do_query

    def do_query (trans, direction, query):
        #python implementation of the 'query' virtual method

Optional. Handle a requested query. Subclasses that implement this must chain up to the parent if they didn't handle the query

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`direction` (Gst.PadDirection) –
No description available
`query` (Gst.Query) –
No description available
Returns (bool) –
No description available

#### set_caps

    gboolean
    set_caps (GstBaseTransform * trans,
              GstCaps * incaps,
              GstCaps * outcaps)

Allows the subclass to be notified of the actual caps set.

Parameters:

`trans` –
No description available
`incaps` –
No description available
`outcaps` –
No description available
Returns –
No description available

#### vfunc_set_caps

    function vfunc_set_caps(trans: GstBase.BaseTransform, incaps: Gst.Caps, outcaps: Gst.Caps): {
        // javascript implementation of the 'set_caps' virtual method
    }

Allows the subclass to be notified of the actual caps set.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`incaps` (Gst.Caps) –
No description available
`outcaps` (Gst.Caps) –
No description available
Returns (Number) –
No description available

#### do_set_caps

    def do_set_caps (trans, incaps, outcaps):
        #python implementation of the 'set_caps' virtual method

Allows the subclass to be notified of the actual caps set.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`incaps` (Gst.Caps) –
No description available
`outcaps` (Gst.Caps) –
No description available
Returns (bool) –
No description available

#### sink_event

    gboolean
    sink_event (GstBaseTransform * trans,
                GstEvent * event)

Optional. Event handler on the sink pad. The default implementation handles the event and forwards it downstream.

Parameters:

`trans` –
No description available
`event` –
No description available
Returns –
No description available

#### vfunc_sink_event

    function vfunc_sink_event(trans: GstBase.BaseTransform, event: Gst.Event): {
        // javascript implementation of the 'sink_event' virtual method
    }

Optional. Event handler on the sink pad. The default implementation handles the event and forwards it downstream.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`event` (Gst.Event) –
No description available
Returns (Number) –
No description available

#### do_sink_event

    def do_sink_event (trans, event):
        #python implementation of the 'sink_event' virtual method

Optional. Event handler on the sink pad. The default implementation handles the event and forwards it downstream.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`event` (Gst.Event) –
No description available
Returns (bool) –
No description available

#### src_event

    gboolean
    src_event (GstBaseTransform * trans,
               GstEvent * event)

Optional. Event handler on the source pad. The default implementation handles the event and forwards it upstream.

Parameters:

`trans` –
No description available
`event` –
No description available
Returns –
No description available

#### vfunc_src_event

    function vfunc_src_event(trans: GstBase.BaseTransform, event: Gst.Event): {
        // javascript implementation of the 'src_event' virtual method
    }

Optional. Event handler on the source pad. The default implementation handles the event and forwards it upstream.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`event` (Gst.Event) –
No description available
Returns (Number) –
No description available

#### do_src_event

    def do_src_event (trans, event):
        #python implementation of the 'src_event' virtual method

Optional. Event handler on the source pad. The default implementation handles the event and forwards it upstream.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`event` (Gst.Event) –
No description available
Returns (bool) –
No description available

#### start

    gboolean
    start (GstBaseTransform * trans)

Optional. Called when the element starts processing. Allows opening external resources.

Parameters:

`trans` –
No description available
Returns –
No description available

#### vfunc_start

    function vfunc_start(trans: GstBase.BaseTransform): {
        // javascript implementation of the 'start' virtual method
    }

Optional. Called when the element starts processing. Allows opening external resources.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
Returns (Number) –
No description available

#### do_start

    def do_start (trans):
        #python implementation of the 'start' virtual method

Optional. Called when the element starts processing. Allows opening external resources.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
Returns (bool) –
No description available

#### stop

    gboolean
    stop (GstBaseTransform * trans)

Optional. Called when the element stops processing. Allows closing external resources.

Parameters:

`trans` –
No description available
Returns –
No description available

#### vfunc_stop

    function vfunc_stop(trans: GstBase.BaseTransform): {
        // javascript implementation of the 'stop' virtual method
    }

Optional. Called when the element stops processing. Allows closing external resources.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
Returns (Number) –
No description available

#### do_stop

    def do_stop (trans):
        #python implementation of the 'stop' virtual method

Optional. Called when the element stops processing. Allows closing external resources.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
Returns (bool) –
No description available

#### submit_input_buffer

    GstFlowReturn
    submit_input_buffer (GstBaseTransform * trans,
                         gboolean is_discont,
                         GstBuffer * input)

Function which accepts a new input buffer and pre-processes it. The default implementation performs caps (re)negotiation, then QoS if needed, and places the input buffer into the queued_buf member variable. If the buffer is dropped due to QoS, it returns GST_BASE_TRANSFORM_FLOW_DROPPED. If this input buffer is not contiguous with any previous input buffer, then is_discont is set to TRUE. (Since: 1.6)

Parameters:

`trans` –
No description available
`is_discont` –
No description available
`input` –
No description available
Returns –
No description available

#### vfunc_submit_input_buffer

    function vfunc_submit_input_buffer(trans: GstBase.BaseTransform, is_discont: Number, input: Gst.Buffer): {
        // javascript implementation of the 'submit_input_buffer' virtual method
    }

Function which accepts a new input buffer and pre-processes it. The default implementation performs caps (re)negotiation, then QoS if needed, and places the input buffer into the queued_buf member variable. If the buffer is dropped due to QoS, it returns GST_BASE_TRANSFORM_FLOW_DROPPED. If this input buffer is not contiguous with any previous input buffer, then is_discont is set to TRUE. (Since: 1.6)

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`is_discont` (Number) –
No description available
`input` (Gst.Buffer) –
No description available
Returns (Gst.FlowReturn) –
No description available

#### do_submit_input_buffer

    def do_submit_input_buffer (trans, is_discont, input):
        #python implementation of the 'submit_input_buffer' virtual method

Function which accepts a new input buffer and pre-processes it. The default implementation performs caps (re)negotiation, then QoS if needed, and places the input buffer into the queued_buf member variable. If the buffer is dropped due to QoS, it returns GST_BASE_TRANSFORM_FLOW_DROPPED. If this input buffer is not contiguous with any previous input buffer, then is_discont is set to TRUE. (Since: 1.6)

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`is_discont` (bool) –
No description available
`input` (Gst.Buffer) –
No description available
Returns (Gst.FlowReturn) –
No description available

#### transform

    GstFlowReturn
    transform (GstBaseTransform * trans,
               GstBuffer * inbuf,
               GstBuffer * outbuf)

Required if the element does not operate in-place. Transforms one incoming buffer to one outgoing buffer. The function is allowed to change size/timestamp/duration of the outgoing buffer.

Parameters:

`trans` –
No description available
`inbuf` –
No description available
`outbuf` –
No description available
Returns –
No description available

#### vfunc_transform

    function vfunc_transform(trans: GstBase.BaseTransform, inbuf: Gst.Buffer, outbuf: Gst.Buffer): {
        // javascript implementation of the 'transform' virtual method
    }

Required if the element does not operate in-place. Transforms one incoming buffer to one outgoing buffer. The function is allowed to change size/timestamp/duration of the outgoing buffer.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`inbuf` (Gst.Buffer) –
No description available
`outbuf` (Gst.Buffer) –
No description available
Returns (Gst.FlowReturn) –
No description available

#### do_transform

    def do_transform (trans, inbuf, outbuf):
        #python implementation of the 'transform' virtual method

Required if the element does not operate in-place. Transforms one incoming buffer to one outgoing buffer. The function is allowed to change size/timestamp/duration of the outgoing buffer.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`inbuf` (Gst.Buffer) –
No description available
`outbuf` (Gst.Buffer) –
No description available
Returns (Gst.FlowReturn) –
No description available

#### transform_caps

    GstCaps *
    transform_caps (GstBaseTransform * trans,
                    GstPadDirection direction,
                    GstCaps * caps,
                    GstCaps * filter)

Optional. Given the pad in this direction and the given caps, what caps are allowed on the other pad in this element ?

Parameters:

`trans` –
No description available
`direction` –
No description available
`caps` –
No description available
`filter` –
No description available
Returns –
No description available

#### vfunc_transform_caps

    function vfunc_transform_caps(trans: GstBase.BaseTransform, direction: Gst.PadDirection, caps: Gst.Caps, filter: Gst.Caps): {
        // javascript implementation of the 'transform_caps' virtual method
    }

Optional. Given the pad in this direction and the given caps, what caps are allowed on the other pad in this element ?

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`direction` (Gst.PadDirection) –
No description available
`caps` (Gst.Caps) –
No description available
`filter` (Gst.Caps) –
No description available
Returns (Gst.Caps) –
No description available

#### do_transform_caps

    def do_transform_caps (trans, direction, caps, filter):
        #python implementation of the 'transform_caps' virtual method

Optional. Given the pad in this direction and the given caps, what caps are allowed on the other pad in this element ?

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`direction` (Gst.PadDirection) –
No description available
`caps` (Gst.Caps) –
No description available
`filter` (Gst.Caps) –
No description available
Returns (Gst.Caps) –
No description available

#### transform_ip

    GstFlowReturn
    transform_ip (GstBaseTransform * trans,
                  GstBuffer * buf)

Required if the element operates in-place. Transform the incoming buffer in-place.

Parameters:

`trans` –
No description available
`buf` –
No description available
Returns –
No description available

#### vfunc_transform_ip

    function vfunc_transform_ip(trans: GstBase.BaseTransform, buf: Gst.Buffer): {
        // javascript implementation of the 'transform_ip' virtual method
    }

Required if the element operates in-place. Transform the incoming buffer in-place.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`buf` (Gst.Buffer) –
No description available
Returns (Gst.FlowReturn) –
No description available

#### do_transform_ip

    def do_transform_ip (trans, buf):
        #python implementation of the 'transform_ip' virtual method

Required if the element operates in-place. Transform the incoming buffer in-place.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`buf` (Gst.Buffer) –
No description available
Returns (Gst.FlowReturn) –
No description available

#### transform_meta

    gboolean
    transform_meta (GstBaseTransform * trans,
                    GstBuffer * outbuf,
                    GstMeta * meta,
                    GstBuffer * inbuf)

Optional. Transform the metadata on the input buffer to the output buffer. By default this method copies all meta without tags. Subclasses can implement this method and return TRUE if the metadata is to be copied.

Parameters:

`trans` –
No description available
`outbuf` –
No description available
`meta` –
No description available
`inbuf` –
No description available
Returns –
No description available

#### vfunc_transform_meta

    function vfunc_transform_meta(trans: GstBase.BaseTransform, outbuf: Gst.Buffer, meta: Gst.Meta, inbuf: Gst.Buffer): {
        // javascript implementation of the 'transform_meta' virtual method
    }

Optional. Transform the metadata on the input buffer to the output buffer. By default this method copies all meta without tags. Subclasses can implement this method and return TRUE if the metadata is to be copied.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`outbuf` (Gst.Buffer) –
No description available
`meta` (Gst.Meta) –
No description available
`inbuf` (Gst.Buffer) –
No description available
Returns (Number) –
No description available

#### do_transform_meta

    def do_transform_meta (trans, outbuf, meta, inbuf):
        #python implementation of the 'transform_meta' virtual method

Optional. Transform the metadata on the input buffer to the output buffer. By default this method copies all meta without tags. Subclasses can implement this method and return TRUE if the metadata is to be copied.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`outbuf` (Gst.Buffer) –
No description available
`meta` (Gst.Meta) –
No description available
`inbuf` (Gst.Buffer) –
No description available
Returns (bool) –
No description available

#### transform_size

    gboolean
    transform_size (GstBaseTransform * trans,
                    GstPadDirection direction,
                    GstCaps * caps,
                    gsize size,
                    GstCaps * othercaps,
                    gsize* othersize)

Optional. Given the size of a buffer in the given direction with the given caps, calculate the size in bytes of a buffer on the other pad with the given other caps. The default implementation uses get_unit_size and keeps the number of units the same.

Parameters:

`trans` –
No description available
`direction` –
No description available
`caps` –
No description available
`size` –
No description available
`othercaps` –
No description available
`othersize` –
No description available
Returns –
No description available

#### vfunc_transform_size

    function vfunc_transform_size(trans: GstBase.BaseTransform, direction: Gst.PadDirection, caps: Gst.Caps, size: Number, othercaps: Gst.Caps): {
        // javascript implementation of the 'transform_size' virtual method
    }

Optional. Given the size of a buffer in the given direction with the given caps, calculate the size in bytes of a buffer on the other pad with the given other caps. The default implementation uses get_unit_size and keeps the number of units the same.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`direction` (Gst.PadDirection) –
No description available
`caps` (Gst.Caps) –
No description available
`size` (Number) –
No description available
`othercaps` (Gst.Caps) –
No description available

Returns a tuple made of:

(Number ) –
No description available
`othersize` (Number ) –
No description available

#### do_transform_size

    def do_transform_size (trans, direction, caps, size, othercaps):
        #python implementation of the 'transform_size' virtual method

Optional. Given the size of a buffer in the given direction with the given caps, calculate the size in bytes of a buffer on the other pad with the given other caps. The default implementation uses get_unit_size and keeps the number of units the same.

Parameters:

`trans` (GstBase.BaseTransform) –
No description available
`direction` (Gst.PadDirection) –
No description available
`caps` (Gst.Caps) –
No description available
`size` (int) –
No description available
`othercaps` (Gst.Caps) –
No description available

Returns a tuple made of:

(bool ) –
No description available
`othersize` (int ) –
No description available

## Function Macros

### GST_BASE_TRANSFORM_CAST

    #define GST_BASE_TRANSFORM_CAST(obj)	((GstBaseTransform *)(obj))

### GST_BASE_TRANSFORM_SINK_PAD

    #define GST_BASE_TRANSFORM_SINK_PAD(obj)	(GST_BASE_TRANSFORM_CAST (obj)->sinkpad)

Gives the pointer to the sink GstPad object of the element.

Parameters:

`obj` –

base transform instance

### GST_BASE_TRANSFORM_SRC_PAD

    #define GST_BASE_TRANSFORM_SRC_PAD(obj)		(GST_BASE_TRANSFORM_CAST (obj)->srcpad)

Gives the pointer to the source GstPad object of the element.

Parameters:

`obj` –

base transform instance

## Constants

### GST_BASE_TRANSFORM_FLOW_DROPPED

    #define GST_BASE_TRANSFORM_FLOW_DROPPED   GST_FLOW_CUSTOM_SUCCESS

A GstFlowReturn that can be returned from transform and transform_ip to indicate that no output buffer was generated.

### GST_BASE_TRANSFORM_SINK_NAME

    #define GST_BASE_TRANSFORM_SINK_NAME	"sink"

The name of the templates for the sink pad.

### GstBase.BASE_TRANSFORM_SINK_NAME

The name of the templates for the sink pad.

### GstBase.BASE_TRANSFORM_SINK_NAME

The name of the templates for the sink pad.

### GST_BASE_TRANSFORM_SRC_NAME

    #define GST_BASE_TRANSFORM_SRC_NAME	"src"

The name of the templates for the source pad.

### GstBase.BASE_TRANSFORM_SRC_NAME

The name of the templates for the source pad.

### GstBase.BASE_TRANSFORM_SRC_NAME

The name of the templates for the source pad.

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