3gppmux

3gppmux — Muxer for 3GPP (.3gp) files

Synopsis


Description

This element merges streams (audio and video) into 3GPP (.3gp) 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 (3gppmux). 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 (movie-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).

dts-method allows selecting a method for managing input timestamps (stay tuned for 0.11 to have this automagically settled). The default delta/duration method should handle nice (aka perfect streams) just fine, but may experience problems otherwise (e.g. input stream with re-ordered B-frames and/or with frame dropping). The re-ordering approach re-assigns incoming timestamps in ascending order to incoming buffers and offers an alternative in such cases. In cases where that might fail, the remaining method can be tried, which is exact and according to specs, but might experience playback on not so spec-wise players. Note that this latter approach also requires one to enable presentation-timestamp.

Example pipelines

1
gst-launch-1.0 v4l2src num-buffers=50 ! queue ! ffenc_h263 ! 3gppmux ! filesink location=video.3gp
Records a video stream captured from a v4l2 device, encodes it into H.263 and muxes it into an 3gp file.

Documentation last reviewed on 2011-04-21

Synopsis

Element Information

plugin

isomp4

author

Thiago Sousa Santos <thiagoss@embedded.ufcg.edu.br>

class

Codec/Muxer

Element Pads

name

audio_%u

direction

sink

presence

request

details

audio/AMR, rate=(int)8000, channels=(int)[ 1, 2 ]

audio/AMR-WB, rate=(int)16000, channels=(int)[ 1, 2 ]

audio/mpeg, mpegversion=(int)1, layer=(int)3, channels=(int)[ 1, 2 ], rate=(int)[ 1, 2147483647 ]

audio/mpeg, mpegversion=(int)4, stream-format=(string)raw, channels=(int)[ 1, 8 ], rate=(int)[ 1, 2147483647 ]

name

video_%u

direction

sink

presence

request

details

video/x-h263, width=(int)[ 16, 4096 ], height=(int)[ 16, 4096 ]

video/mpeg, mpegversion=(int)4, systemstream=(boolean)false, width=(int)[ 16, 4096 ], height=(int)[ 16, 4096 ]

video/x-divx, divxversion=(int)5, width=(int)[ 16, 4096 ], height=(int)[ 16, 4096 ]

video/x-h264, stream-format=(string)avc, alignment=(string)au, width=(int)[ 16, 4096 ], height=(int)[ 16, 4096 ]

name

src

direction

source

presence

always

details

video/quicktime, variant=(string)3gpp

Details