Category Archives: MP4

Official AV1 and VP9 support in GPAC

Dear reader,

GPAC has added support for new codecs recently:

  • AV1 support is available in nightly builds since July 10th, 2018. This include file creation with MP4Box (including MPEG DASH generation) and file playback with MP4Client. Support for AV1 encryption was added on September 20th, 2018.
  • VP9 support was completed on October 14th, 2018.

This article gives you some useful command lines to use AV1 streams, but the same can be applied for VP9 streams.

Command-line for importing AV1 streams into MP4 files

To store an AV1 bitstream into an ISOBMFF/MP4 file , use the following command line. If the input file is called *.av1, its content can be OBUs (as specified in Section 5 of the AV1 specification), IVF or Annex B bitstreams. WebM streams are not supported. You can also call OBU-based bistream *.obu and IVF files *.ivf:

MP4Box -add file.av1 file_av1.mp4

If your file extension is not recognized by MP4Box, you can indicate the bitstream format with “:fmt=obu” or :fmt=AnnexB or fmt=IVF (case insensitive) as follows:

MP4Box -add file_av1.mp4

AV1 bitstreams may not contain frame rate information, you can use the following to indicate it:

MP4Box -add file.av1:fps=1000 file_av1.mp4

Command-line for AV1 adaptive streaming preparation

You can use the usual MP4Box command line parameters to segment your AV1 MP4 file and prepare it for adaptive streaming. The following command line will generate an MPEG-DASH onDemand manifest based on an AV1 representation (with its ‘codecs’ parameter) and it will create a segmented MP4 file with segments starting at AV1 KEY FRAMEs and targeting 1 second duration.

MP4Box -dash 1000 -profile onDemand file_av1.mp4

Command-line for AV1 encryption/decryption

Encryption of AV1 streams in MP4 files follows the general principles given by MPEG’s Common Encryption specification.¬† To use MP4Box for encryption or decryption, use the following command lines where the file ‘info.xml’ is an XML file that provides encryption parameters, as described in more details here. Example of such XML files can be found in our test base.


MP4Box -crypt info.xml -out file_av1_encrypted.mp4 file_av1.mp4


MP4Box -decrypt info.xml -out file_av1_decrypted.mp4 file_av1_encrypted.mp4

Acknowledgements and conclusion

The work on AV1 and VP9 was largely sponsored by Alliance for Open Media and Netflix. Kudos to them ūüôā

As usual, if you find any bug or miss documentation, let us know.

Subtitling with GPAC

‚ö† The content of this page may be outdated.
Please refer to this page for more up to date information:


This post is the first post in a series I’m writing¬†to help you discover the many different ways to handle tracks in MP4 files using MP4Box and other GPAC tools, with a particular focus on three types of tracks: subtitles, metadata and graphics tracks. Let me start in this post with subtitle tracks. Continue reading Subtitling with GPAC

MP4 demuxer examples

‚ö† The content of this page may be outdated.
Please refer to this page for more up to date information:


Dear followers,

At the request of some people, we have added to GPAC some sample applications demonstrating how to use GPAC to demux MP4 files. They are not full applications, just examples taking some MP4 files as input and displaying some information about the media samples contained in the file.

So far, we have added 3 sample applications:

  • a basic demuxer called ‘bmp4demux’ capable of reading and dispatching media access units from fragmented or non-fragmented MP4 files, progressively (i.e. while the file is being written);
  • a segment based demux called ‘segmp4demuxer‘¬†capable of dispatching media units from media segments, where the input data is framed.¬†¬†This is what is used for the DASH support;
  • and a more advanced demuxer, called ‘fmp4demux’ capable of dispatching media units in streaming mode (i.e. reclaiming resources once media units have been dispatched), where the input data comes from fragmented mp4 but is not framed, i.e. the data in the buffer passed to the demuxer does not start or end at segment or fragment boundaries.

Continue reading MP4 demuxer examples