# qtmux

This element merges streams (audio and video) into QuickTime(.mov) files.

The following background intends to explain why various similar muxers are present in this plugin.

The QuickTime file format specification served as basis for the MP4 file format specification (mp4mux), and as such the QuickTime file structure is nearly identical to the so-called ISO Base Media file format defined in ISO 14496-12 (except for some media specific parts).

In turn, the latter ISO Base Media format was further specialized as a Motion JPEG-2000 file format in ISO 15444-3 (mj2mux) and in various 3GPP(2) specs (gppmux). The fragmented file features defined (only) in ISO Base Media are used by ISMV files making up (a.o.) Smooth Streaming (ismlmux).

A few properties (#GstBaseQTMux:movie-timescale, trak-timescale, trak-timescale) allow adjusting some technical parameters, which might be useful in (rare) cases to resolve compatibility issues in some situations.

Some other properties influence the result more fundamentally. A typical mov/mp4 file's metadata (aka moov) is located at the end of the file, somewhat contrary to this usually being called "the header". However, a faststart file will (with some effort) arrange this to be located near start of the file, which then allows it e.g. to be played while downloading. Alternatively, rather than having one chunk of metadata at start (or end), there can be some metadata at start and most of the other data can be spread out into fragments of fragment-duration. If such fragmented layout is intended for streaming purposes, then streamable allows foregoing to add index metadata (at the end of file).

When the maximum duration to be recorded can be known in advance, qtmux also supports a 'Robust Muxing' mode. In robust muxing mode, space for the headers are reserved at the start of muxing, and rewritten at a configurable interval, so that the output file is always playable, even if the recording is interrupted uncleanly by a crash. Robust muxing mode requires a seekable output, such as filesink, because it needs to rewrite the start of the file.

To enable robust muxing mode, set the reserved-moov-update-period and reserved-max-duration property. Also present is the reserved-bytes-per-sec property, which can be increased if for some reason the default is not large enough and the initial reserved space for headers is too small. Applications can monitor the reserved-duration-remaining property to see how close to full the reserved space is becoming.

Applications that wish to be able to use/edit a file while it is being written to by live content, can use the "Robust Prefill Muxing" mode. That mode is a variant of the "Robust Muxing" mode in that it will pre-allocate a completely valid header from the start for all tracks (i.e. it appears as though the file is "reserved-max-duration" long with all samples present). This mode can be enabled by setting the reserved-moov-update-period and reserved-prefill properties. Note that this mode is only possible with input streams that have a fixed sample size (such as raw audio and Prores Video) and that don't have reordered samples.

## Example pipelines

     gst-launch-1.0 v4l2src num-buffers=500 ! video/x-raw,width=320,height=240 ! videoconvert ! qtmux ! filesink location=video.mov

Records a video stream captured from a v4l2 device and muxes it into a qt file.

## Hierarchy

    GObject
        ╰──GInitiallyUnowned
            ╰──GstObject
                ╰──GstElement
                    ╰──GstAggregator
                        ╰──GstBaseQTMux
                            ╰──qtmux

## Implemented interfaces

    GstTagSetter
    GstTagXmpWriter
    GstPreset

## Factory details

Authors: – Thiago Sousa Santos

Classification: – `Codec/Muxer`

Rank – primary

Plugin – isomp4

Package – GStreamer Good Plug-ins

## Pad Templates

### `audio_%u`

    audio/x-raw:
             format: { S32LE, S32BE, S24LE, S24BE, S16LE, S16BE, S8, U8 }
             layout: interleaved
           channels: [ 1, 2 ]
               rate: [ 1, 2147483647 ]
    audio/x-raw:
             format: { S32LE, S32BE, S24LE, S24BE, S16LE, S16BE, S8, U8 }
             layout: interleaved
       channel-mask: 0x0000000000000000
           channels: [ 1, 16 ]
               rate: [ 1, 2147483647 ]
    audio/mpeg:
        mpegversion: 1
              layer: [ 1, 3 ]
           channels: [ 1, 2 ]
               rate: [ 1, 2147483647 ]
    audio/mpeg:
        mpegversion: 4
      stream-format: raw
           channels: [ 1, 8 ]
               rate: [ 1, 2147483647 ]
    audio/x-ac3:
           channels: [ 1, 6 ]
               rate: [ 1, 2147483647 ]
    audio/x-adpcm:
             layout: dvi
        block_align: [ 64, 8096 ]
           channels: [ 1, 2 ]
               rate: [ 1, 2147483647 ]
    audio/x-alaw:
           channels: [ 1, 2 ]
               rate: [ 1, 2147483647 ]
    audio/x-mulaw:
           channels: [ 1, 2 ]
               rate: [ 1, 2147483647 ]
    audio/AMR:
               rate: 8000
           channels: [ 1, 2 ]
    audio/AMR-WB:
               rate: 16000
           channels: [ 1, 2 ]
    audio/x-alac:
           channels: [ 1, 2 ]
               rate: [ 1, 2147483647 ]
    audio/x-opus:
    channel-mapping-family: [ 0, 255 ]
           channels: [ 1, 8 ]
               rate: [ 1, 2147483647 ]

Presence – request

Direction – sink

Object type – GstQTMuxPad

### `caption_%u`

    closedcaption/x-cea-608:
             format: s334-1a
    closedcaption/x-cea-708:
             format: cdp

Presence – request

Direction – sink

Object type – GstQTMuxPad

### `src`

    video/quicktime:
            variant: apple
    video/quicktime:

Presence – always

Direction – src

Object type – GstAggregatorPad

### `subtitle_%u`

    text/x-raw:
             format: utf8

Presence – request

Direction – sink

Object type – GstQTMuxPad

### `video_%u`

    video/x-raw:
             format: { RGB, UYVY, v210 }
              width: [ 16, 2147483647 ]
             height: [ 16, 2147483647 ]
    video/mpeg:
        mpegversion: 4
       systemstream: false
              width: [ 16, 2147483647 ]
             height: [ 16, 2147483647 ]
    video/x-divx:
        divxversion: 5
              width: [ 16, 2147483647 ]
             height: [ 16, 2147483647 ]
    video/x-prores:
            variant: { (string)standard, (string)lt, (string)hq, (string)proxy, (string)4444, (string)4444xq }
              width: [ 16, 2147483647 ]
             height: [ 16, 2147483647 ]
    video/x-cineform:
              width: [ 16, 2147483647 ]
             height: [ 16, 2147483647 ]
    video/x-h263:
              width: [ 16, 2147483647 ]
             height: [ 16, 2147483647 ]
    video/x-h264:
      stream-format: { (string)avc, (string)avc3 }
          alignment: au
              width: [ 16, 2147483647 ]
             height: [ 16, 2147483647 ]
    video/x-h265:
      stream-format: { (string)hvc1, (string)hev1 }
          alignment: au
              width: [ 16, 2147483647 ]
             height: [ 16, 2147483647 ]
    video/x-svq:
         svqversion: 3
              width: [ 16, 2147483647 ]
             height: [ 16, 2147483647 ]
    video/x-dv:
       systemstream: false
              width: [ 16, 2147483647 ]
             height: [ 16, 2147483647 ]
    image/jpeg:
              width: [ 16, 2147483647 ]
             height: [ 16, 2147483647 ]
    image/png:
              width: [ 16, 2147483647 ]
             height: [ 16, 2147483647 ]
    video/x-vp8:
              width: [ 16, 2147483647 ]
             height: [ 16, 2147483647 ]
    video/x-vp9:
            profile: { (string)0, (string)1, (string)2, (string)3 }
      chroma-format: { (string)4:2:0, (string)4:2:2, (string)4:4:4 }
              width: [ 16, 2147483647 ]
             height: [ 16, 2147483647 ]
    video/x-dirac:
              width: [ 16, 2147483647 ]
             height: [ 16, 2147483647 ]
    video/x-qt-part:
              width: [ 16, 2147483647 ]
             height: [ 16, 2147483647 ]
    video/x-av1:
      stream-format: obu-stream
          alignment: tu
              width: [ 16, 2147483647 ]
             height: [ 16, 2147483647 ]

Presence – request

Direction – sink

Object type – GstQTMuxPad

## Properties

### streamable

    “streamable” gboolean

If set to true, the output should be as if it is to be streamed and hence no indexes written or duration written. (DEPRECATED, only valid for fragmented MP4)

Flags : Read / Write / Construct

Default value : false

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