FFmpeg Summer Of Code 2009

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Current Status

This list is still a work-in-progress, please see also the Talk Page.

Qualification tasks

For us to consider your application for SoC we require a completed qualification task. Choose a task from the Small Tasks list, send an email to FFmpeg-devel mailing list to inform that you are working on it (to avoid duplicated work) and when it is ready submit it for review at FFmpeg-devel. The task is considered completed when your patch is accepted to our main SVN tree.

Before posting to ffmpeg-devel, make sure you read and understand our netiquette guidelines, especially avoid top-posting. Before you send us your patch, read our development guidelines and make sure your patch fulfills all the requirements stated there. You should also familiar with the programs diff, patch and Subversion. You have to learn these basics on your own before you start, we will not teach them to you during the application process.

A completed FFmpeg qualifications task is also accepted as a qualification task for the VLC organization (does NOT include x264).

1st Tier Project Proposals

1st tier project proposals are project ideas that are reasonably well defined AND have a mentor volunteered.

S/PDIF muxer

  • Info: Spdif
  • Implement a muxer capable to mux:
    • DTS, all 3 packing modes and the usable HD extensions
    • AC3, eAC3 also
    • PCM
    • WMApro
    • AAC
    • Mpeg-audio, layer 2 and 3

Implement support in ffplay so that it is possible to output the audio stream over S/PDIF when playing a media file.

Mentor: Benjamin Larsson, Andreas Öman

Flash Screen video 2 codec

Mentor: Benjamin Larsson

MPEG-4 ALS decoder

  • primary goal: stream copy of ALS frames in MP4 files from the reference encoder
    • detect codec_id
    • preserve extradata
  • primary goal: write the decoder based on the ISO specification
    • ISO/IEC 14496-3:2005/Amd.2:2006, related corrigenda, and other pertinent ISO documents
  • primary goal: decode files with basic ALS features
    • integer samples
    • LPC
    • rice coding
    • joint-stereo
  • secondary goal: decode files with more advanced ALS features
    • floating-point samples
    • block switching
    • LTP (long term prediction)
    • BGMC (arithmetic coding)
    • MCC (advanced multi-channel)
    • RLSLMS (backward-adaptive prediction)
  • secondary goal: pass the ISO conformance tests
  • secondary goal: handle anything the reference encoder can come up with

Mentor: Justin Ruggles

RTMP Support (Flash streaming)

  • primary goal: implement a RTMP URLProtocol and/or demuxer if needed.
  • secondary goal: extend FFserver to support RTMP streaming.
    • implementation must be compatible with Flash plugin.

Mentor: Baptiste Coudurier

Playlist/Concatenation Support

  • primary goal: implement a playlist/concatenation interface to transcode(FFmpeg) and play(FFplay) media
    • interface will use commandline switches.
    • interface must support every input format FFmpeg support
    • interface must work with different input stream parameters (different formats, codecs, video resolution, audio sample rate, audio channels, etc..)
    • interface must support track selection
    • interface must support existing playlist format files .m3u, .pls, xpsf.

Mentor: Baptiste Coudurier

NEW Seeking API

  • primary goal: implement a new seeking API in libavformat
    • implement av_seek_file in libavformat
    • implement compatible new seek_file for all AVInputFormat porting existing seek function if possible.
    • implement av_build_index function which will build an AVIndex for the file
    • implement av_export_index function which will save AVIndex in a file which can be loaded later.

Mentor: Baptiste Coudurier

Improve RTSP/RTP layer

  • primary goal: cleanup code the structure
  • primary goal: improve the receiver compatibility
  • secondary goal: provide an API to expose the rtcp layer (and the equivalent in RDT dialect)
  • secondary goal: try to support subtitle streams (either as rtcp-xr or application/text stream)
  • secondary goal: make VideoLanClient, MPlayer and Xine use ffmpeg rtsp

Mentor: Luca Barbato, Ronald S. Bultje

AACS implementation

  • Add the ability to encode and decode using Advanced Access Content System to FFmpeg.
  • Specifications: http://www.aacsla.com/specifications/
  • existing implementation e.g. DumpHD: http://forum.doom9.org/showthread.php?t=123111
  • Most parts (BD-J, MKB, title key generation) probably do not belong into FFmpeg, this should be discussed with us before submitting an application
    • possible solution: only implement "lowest" level (decode given the correct title key) but implement CSS en- and decryption as secondary goal

Mentor: Reimar Döffinger

Libavfilter video work

Libavfilter is the FFmpeg filtering library that started as a 2007 SoC project. It should replace the now removed vhook subsystem. Most of it is already part of the FFmpeg main source tree, but there a few bits remaining. This project would consist in the following tasks

  • Get the remaining bits of the SoC tree committed, including the ffmpeg.c and ffplay.c patch
  • Get libavfilter enabled in the main SVN tree
  • Write a watermark filter (this is one of the most commonly requested FFmpeg feature)
  • Write a expand/pad filter (see [1] and [2]
  • Port all MPlayer filters at libmbcodec/vf_* (do not forget asking the authors if it is ok to release them under the LGPL)

see also this ffmpeg-devel message: [3]

Mentor: To be determined, Vitor Sessak if no one else shows up

Libavfilter audio work

At the moment, FFmpeg filtering library has no support at all for handling audio. This task would consist of

  • Expanding the libavfilter framework to work with audio
  • Writing a resampling/format conversion filter (starting with just a wrapping code at libavcodec/resample.c)
    • Can it be made clear that ideally we'd want N-channel resampling? Rob
      • I'm listing here the tasks in the order I'd want see them done chronologically. I think first of all he should write a filter that is just a wrapper (and nothing more) of the code in resample.c. Making it more general is my point #4. I'm trying to focus in getting the general infrastructure in SVN, even if without a lot of fancy filters. Vitor 17:52, 22 March 2009 (EDT)
  • Implement negotiation of sample format and number of channels analogously to the libavfilter colorspace negotiation
    • Does this imply a channel mixing filter? This would be the second most desirable basic audio filter in my opinion. Rob
      • Yes, but it to begin with, he could just write a wrapper around libavcodec/resample.c (see my next point) Vitor 17:52, 22 March 2009 (EDT)
  • Make the resampling filter works for several combinations of sample format and channels
  • Write a visualization filter as proof-of-concept of a filter that works with both video and audio

Mentor: To be determined, Vitor Sessak if no one else shows up

AMR-NB decoder

  • Continue and complete the fundamental debugging of the floating point AMR-NB decoder
  • Implement/reuse the missing post filters
  • Clean up the code, refactor it as appropriate to share code with QCELP and others
  • Submit for review and tend to review comments
  • Implement further non-essential features such as comfort noise

Mentor: Robert Swain

QCELP decoder missing features

  • Implement missing features in the QCELP decoder

Mentor: Robert Swain

This task is probably too small on its own so if you would like to do it, also look at the completion of the AMR-NB decoder task above as they may be merged into one CELP task. --Robert Swain

2nd Tier Project Proposals

All that separates these proposals from their 1st tier brethren is a mentor.

Finish SoC projects from previous years

Some projects are lingering in the dark unfinished. They should be picked up and made ready for inclusion. These projects are potentially less involved than starting from scratch, but also more useful for FFmpeg since the probability that the projects get finished should be higher. If some of them are deemed too easy, they could be combined.

Unfinished projects from previous years are:



For the current status of all SoC projects up to date, see FFmpeg Summer Of Code.

Implement a better regressions test system

  • Split up the current regtests
  • Add tests for all the missing formats and codecs to FATE

Finish ACELP.NET / G.729 decoder

Some parts of a ACELP.net / G.729 decoder are inside and outside of FFmpeg, see the entry on the interesting patches page. They need to get cleaned up, finished and integrated.


  • Port MPlayer's libvo to ffplay
  • Note that this does not just mean to produce a working hack so that ffplay can use xv, but a clean and acceptable wrapper for (most of) libvo.

GStreamer input

  • Like we have vfw input we could have a gstreamer input format also. This would enable support of wmapro and wmalossless until these formats are RE'd. GStreamer input support could possible also enable DRM support, even under Linux/Unix.

Mentor: Christian Schaller

AMR-WB Decoder

Also see AMR.

GSM Decoder

Also see GSM.

Sipr Decoder

Also see RealAudio sipr and this patch.

Speex Decoder

Also see Speex.

AMR-NB Encoder

Also see AMR.

VP6 Encoder

WMV3 Encoder

  • Clearly defined task
  • Primary goal: Encode video sequences such that they can be decoded by a Windows Media player.

This could either be done by improving this patch or by writing the encoder from scratch.

Improve subtitle support

  • Add text-to-bitmap conversion functions
  • One with hard-coded bitmaps for characters
  • One that utilizes freetype
  • Function used will be chosen upon compilation

Adjust existing subtitle support to new ABI

VC-1 Interlaced Support

  • Add support for interlaced streams as used in Bluray recordings to the VC-1 decoder.
  • This includes fixing some reference streams

Improve Ratecontrol

  • Primary goal 1: Fast heuristic VBV compliant per macroblock ratecontrol which has a better PSNR/bitrate and better subjective quality/bitrate than the current code.
  • Primary goal 2: VBV compliant, rate distortion optimal per macroblock ratecontrol using the viterbi algorithm.
  • Secondary goal 1: Fast heuristic scene change detection which detects scene changes more accurately, has better PSNR/bitrate and subjective quality/bitrate than the current heuristic.
  • Secondary goal 2: Rate distortion optimal (for the current picture) scene change detection.
  • Secondary goal 3: B frames decision which is faster and or has a higher PSNR/bitrate and subjective quality/bitrate than the current code.

WMA lossless

WTV (de)muxer

  • Implement a demuxer (and possibly a muxer) for the WTV file format.