FFmpeg Summer of Code 2013: Difference between revisions

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(→‎MPEG-4 ALS encoder: remove some irrelevant parts)
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'''Qualification task:''' write one subtitles demuxer and decoder (for example support for Spruce subtitles format). This is in order to make sure the subtitles chain is understood.
'''Qualification task:''' write one subtitles demuxer and decoder (for example support for Spruce subtitles format). This is in order to make sure the subtitles chain is understood.


'''Mentor:''' Clément Bœsch (''ubitux'' on IRC).
'''Mentor:''' Clément Bœsch (''ubitux'' on IRC)
 
'''Backup Mentor:''' Nicolas George


== Postproc optimizations ==
== Postproc optimizations ==

Revision as of 14:35, 21 March 2013

Google Summer of Code is a program that offers students stipends to write code for open source projects. FFmpeg participated to several past editions, and this page is about the Google Summer of Code 2013 edition. In particular, see timeline.

Application period starts on March 18, and March 29 at 19:00 UTC is the application deadline for interested organizations. Please finish up this page before then.

Proposing Ideas

If you have a project idea please contact a developer first at the #ffmpeg-devel IRC channel on Freenode or via the ffmpeg-devel mailing list. A good source of ideas is the FFmpeg bug tracker and FFmpeg Summer of Code 2012 Ideas List.

When adding an idea follow this template for consistency:

== Task Title ==

'''Description:''' A few sentences or a short paragraph describing the task.

'''Expected results:''' Bulleted list or paragraph describing what the student is expected to achieve.

'''Prerequisites:''' Skills or knowledge required by student.

'''Qualification Task:''' Small task student should perform to demonstrate understanding.

'''Mentor:''' List mentor and backup mentor if there is one and contact info such as IRC name or email address.

Mentored tasks

H.264 Multiview Video Coding (MVC)

Mmspg-epfl-ch-double-camera.jpg

Description: MVC samples exist and the codec is used on Bluray media, but FFmpeg is missing a decoder. Since this task also consists of some changes in the current architecture, it is especially important that this task is discussed on the ffmpeg-devel mailing list.

Expected results: Create MVC decoder and add a test for the FFmpeg Automated Testing Environment (FATE).

Prerequisites: C coding skills, familiarity with git/source code control systems.

Qualification Task: Perform work that demonstrates understanding of MVC and that is a subpart of the whole MVC implementation.

Mentor: Michael Niedermayer (michaelni on IRC).

Animated Portable Network Graphics (APNG)

Description: FFmpeg currently does not support Animated PNGs.

Specification: https://wiki.mozilla.org/APNG_Specification

Animated PNG example bouncing beach ball.png

Expected results:

  • APNG demuxer
    • implement robust probing:
      • PNG images are not misdetected as APNG animations
      • APNG animations are not misdetected as PNG images
    • splits stream into sensible packets (so they can be easily reused in APNG muxer)
    • survives fuzzing (zzuf)
    • add FATE coverage, coverage should be at least 70%
    • test code under valgrind so no invalid reads/writes happen
  • APNG decoder
    • use existing PNG decoder code (write decoder in same file)
    • implement parsing of all APNG chunks (acTL, fcTL, fdAT)
    • error handling
    • survives fuzzing (zzuf)
    • add test for FATE, coverage should be at least 75%
    • CRC checksum validation
    • test code under valgrind so no invalid reads/writes happen
  • APNG muxer && APNG encoder
    • use existing PNG encoder code (write encoder in same file)
    • write compliant files, make sure they play correctly in major web browsers that support APNG
    • add test for FATE

Prerequisites: C coding skills, familiarity with git/source code control systems.

Qualification Task: Implement format autodetection for imagepipe & image demuxer

Mentor: Paul B Mahol

Misc Libavfilter extension

Lavfi-gsoc-filter-vintage-illustration.jpg

Description: Libavfilter is the FFmpeg filtering library. It currently supports audio and video filtering and generation support. This work may focus on porting, fixing, extending, or writing new audio and video filters from scratch.

Candidate filters for porting may be the remaining MPlayer filters currently supported through the mp wrapper, libaf MPlayer filters, and filters from other frameworks (e.g. mjpegtools, transcode, avisynth, virtualdub, etc.). In case of mp ports, the student should verify that the new filter produces the same output and is not slower.

Some ideas for more filters:

  • a frequency filtering domain filter relying on the FFT utils in libavcodec
  • a controller filter which allows to send commands to other filters (e.g. to adjust volume, contrast, etc.), e.g. like the sendcmd filter but through an interactive GUI
  • a lua scripting filter, which allows to implement filtering custom logic in lua

For more ideas check: trac libavfilter tickets.

Expected results: Write or port audio and video filters and possibly fix/extend libavfilter API and design when required.

Prerequisites: C coding skills, familiarity with git/source code control systems. Some background on DSP and image/sound processing techniques would be a bonus but is not strictly required.

Qualification task: write or port one or more filters

Mentor: Stefano Sabatini.

Backup mentor: Clément Bœsch (ubitux on IRC).

Subtitles

Description: FFmpeg has been working on improving its subtitles support recently, notably by adding the support for various text subtitles and various hardsubbing (burning the subtitles onto the video) facilities. While the theme may sound relatively simple compared to audio/video signal processing, the project carry an historical burden not easy to deal with, and introduces various issues very specific to its sparse form.

Subtitles-sensei.jpg

Expected results:

  • Add support for new subtitles formats. Example: a demuxer for .SUP files, just like VobSub but for Blu-Ray, or a VobSub muxer.
  • Improve text subtitles decoders. Typically, this can be supporting advanced markup features in SAMI or WebVTT.
  • Update the API to get rid of the clumsy internal text representation of styles
  • Proper integration of subtitles into libavfilter. This is the ultimate goal, as it will notably allow a complete subtitles rendering for applications such as ffplay.
  • BONUS: if everything goes well, the student will be allowed to add basic support for teletext

Prerequisites: C coding skills, familiarity with git/source code control systems. Some background in fansubbing area (notably ASS experience) would be a bonus but is not strictly required.

Qualification task: write one subtitles demuxer and decoder (for example support for Spruce subtitles format). This is in order to make sure the subtitles chain is understood.

Mentor: Clément Bœsch (ubitux on IRC)

Backup Mentor: Nicolas George

Postproc optimizations

PostProc.jpg

Description: FFmpeg contains libpostproc, which is used to postprocess 8x8 DCT-MC based video and images (jpeg, mpeg-1/2/4, H263 amongth others). The code though has been written a long time ago and its SIMD optimizations need to be updated to what modern CPUs support (AVX2 and SSE2+).

Expected results:

  • Convert all gcc inline asm in libpostproc to YASM.
  • Restructure the code so that it works with block sizes compatible with modern SIMD.
  • Add Integer SSE2 and AVX2 optimizations for each existing MMX/MMX2/3dnow optimization in libpostproc.

Prerequisites: C coding skills, good x86 assembly coding skills, familiarity with git/source code control systems.

Qualification task: convert 1 or 2 MMX2 functions to SSE2 and AVX2.

Mentor: Michael Niedermayer (michaelni on IRC).


Bayer RGB colorspaces

350px-Bayer pattern on sensor.svg.png

Description: Several image and video format store pixels using Bayer-pattern colorspaces. Supporting these format would broaden FFmepg's applicability to RAW still and video photography processing. Tasks:

Expected Results:

  • Rebase existing patches
  • Implement bayer transformations in libswscale (plain C)
  • Add bayer formats to the libavutil pixfmt enumeration routines
  • SIMD optimizations of the libswscale transformations
  • Complete PhotoCINE demuxer to support Bayer format; (or another format of your choosing)

Optional goodies:

  • Extend TIFF decoder to support DNG-Bayer format
  • Support a popular proprietary camera format (many to choose from; see dcraw project)

Qualification task: TBD

Mentor: Peter Ross


MPEG-4 ALS encoder

Description: A MPEG-4 ALS decoder was implemented several years ago but an encoder is still missing in the official codebase. A rudimentary encoder has already been written and is available on github. For this task, that encoder is first to be updated to fit into the current codebase of FFmpeg and to be tested for conformance using the reference codec and specifications. Second, the encoder is to be brought through the usual reviewing process to hit the codebase at the end of the project.

Expected results:

  • Update the existing encoder to fit into the current codebase.
  • Ensure conformance of the encoder by verifying using the reference codec and generate a test case for FATE.
  • Ensure the FFmpeg decoder processes all generated files without warnings.
  • Enhance the rudimentary feature set of the encoder.

Prerequisites: C coding skills, familiarity with git/source code control systems. A certain interest in audio coding and/or knowledge about the FFmpeg codebase could be beneficial.

Qualification task: Add floating point support to MPEG-4 ALS decoder

Mentor: Paul B Mahol (durandal_1707 on irc)


Unmentored tasks

glplay

Opengl logo.jpg

Description: The SDL library that is used by FFplay has some deficiencies, adding OpenGL output to FFplay should allow for better performance (and less bugs at least for some hardware / driver combinations). This could be a new application (glplay), but it is probably simpler to extend ffplay to use OpenGL. You can use code from MPlayer's OpenGL vo module which may be relicensed under the LGPL.

Mentor: TBD Backup: Reimar Döffinger


AAC

Description: FFmpeg contains an AAC encoder and decoder, both of them can be improved in various ways. This is enough work for more than one GSoC project, so one part of your submission would be to define on which task exactly you want to work.

  • AAC LD decoder
  • AAC BSAC decoder: This has already been started, but the existing decoder still fails on many samples
  • AAC SSR decoder
  • AAC 960/120 MDCT window
  • AAC multi-channel encoding

See also the FFmpeg bug tracker for AAC issues, fixing one of them or rebasing the existing incomplete BSAC decoder for current git head fixing one or more existing bugs are possible qualification tasks.

DTS / DCA

Description: FFmpeg contains a DTS decoder.

  • DTS-HD decoder improvements: A possible qualification task is to implement ticket #1920
    • Add support for X96 extension (96khz)
    • Add support for XLL extension (lossless)
    • Add support for pure DTS-HD streams that do not contain a DTS core
    • Add support for multiple assets
    • Add support for LBR extension

TrueHD encoder

Description: FFmpeg currently does not support encoding to one of the lossless audio formats used on Bluray discs. This task consists of implementing a TrueHD encoder that allows to losslessly encode audio to play it on hardware devices capable of TrueHD decoding.

Opus decoder

Opus.png

Description: Opus decoding is currently supported through the external libopus library

  • Write a native decoder, continue working on the existing unfinished implementation

A possible qualification task is to port the existing incomplete decoder to current git head and improve it to show that you are capable of working on this task.

VC-1 interlaced

Description: The FFmpeg VC-1 decoder has improved over the years, but many samples are still not decoded bit-exact and real-world interlaced streams typically show artefacts.

  • Implement missing interlace features
  • Make more reference samples bit-exact

As a qualification task, you should try to find a bug in the current decoder implementation and fix it.

JPEG 2000

Jpeg2000.jpg

Description: FFmpeg contains an experimental native JPEG 2000 encoder and decoder. Both are missing many features, see also the FFmpeg bug tracker for some unsupported samples. Work on an issue (for example from the bug tracker) as a qualification task to show that you are capable of improving the codec implementation.


VP7

Description: Not many VP7 samples are in the wild, but no open-source decoder exists although a specification exists. Write a decoder that reuses as much as possible of existing FFmpeg code, it is likely that functions of the existing decoders for On2-based formats will be useful.