[FFmpeg-cvslog] [ffmpeg-web] branch master updated. 2c8a298 ffmpeg/web/index: add news describing GSoC 2015 program outcome
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commit 2c8a29870f1a8d5f03aad1db84cb9790c140d32e
Author: Stefano Sabatini <stefasab at gmail.com>
AuthorDate: Sun Sep 27 14:36:16 2015 +0200
Commit: Stefano Sabatini <stefasab at gmail.com>
CommitDate: Tue Sep 29 09:07:43 2015 +0200
ffmpeg/web/index: add news describing GSoC 2015 program outcome
Description for each project was provided by each mentor.
diff --git a/src/index b/src/index
index 9d12a7b..77946a4 100644
--- a/src/index
+++ b/src/index
@@ -37,6 +37,240 @@
News
</h1>
+ <a id="gsoc2015_result"></a><h3>September 29th, 2015, GSoC 2015 results</h3>
+
+ <p>
+ FFmpeg participated to the latest edition of
+ the <a href="http://www.google-melange.com/gsoc/homepage/google/gsoc2015">Google
+ Summer of Code</a> Project. FFmpeg got a total of 8 assigned
+ projects, and 7 of them were successful.
+ </p>
+
+ <p>We want to thank <a href="https://www.google.com">Google</a>, the
+ participating students, and especially the mentors who joined this
+ effort. We're looking forward to participating in the next GSoC
+ edition!
+ </p>
+
+ <p>
+ Below you can find a brief description of the final outcome of
+ each single project.
+ </p>
+
+ <h4>Basic servers for network protocols, mentee: Stephan Holljes, mentor: Nicolas George</h4>
+
+ <p>
+ Stephan Holljes's project for this session of Google Summer of Code was to
+ implement basic HTTP server features for libavformat, to complement the
+ already present HTTP client and RTMP and RTSP server code.
+ </p>
+
+ <p>
+ The first part of the project was to make the HTTP code capable of accepting
+ a single client; it was completed partly during the qualification period and
+ partly during the first week of the summer. Thanks to this work, it is now
+ possible to make a simple HTTP stream using the following commands:
+ <pre>
+ ffmpeg -i /dev/video0 -listen 1 -f matroska \
+ -c:v libx264 -preset fast -tune zerolatency http://:8080
+ ffplay http://localhost:8080/
+ </pre>
+ </p>
+
+ <p>
+ The next part of the project was to extend the code to be able to accept
+ several clients, simultaneously or consecutively. Since libavformat did not
+ have an API for that kind of task, it was necessary to design one. This part
+ was mostly completed before the midterm and applied shortly afterwards.
+ Since the ffmpeg command-line tool is not ready to serve several clients,
+ the test ground for that new API is an example program serving hard-coded
+ content.
+ </p>
+
+ <p>
+ The last and most ambitious part of the project was to update ffserver to
+ make use of the new API. It would prove that the API is usable to implement
+ real HTTP servers, and expose the points where more control was needed. By
+ the end of the summer, a first working patch series was undergoing code
+ review.
+ </p>
+
+ <h4>Browsing content on the server, mentee: Mariusz Szczepańczyk, mentor: Lukasz Marek</h4>
+
+ <p>
+ Mariusz finished an API prepared by the FFmpeg community and implemented
+ Samba directory listing as qualification task.
+ </p>
+
+ <p>
+ During the program he extended the API with the possibility to
+ remove and rename files on remote servers. He completed the
+ implementation of these features for file, Samba, SFTP, and FTP
+ protocols.
+ </p>
+
+ <p>
+ At the end of the program, Mariusz provided a sketch of an
+ implementation for HTTP directory listening.
+ </p>
+
+ <h4>Directshow digital video capture, mentee: Mate Sebok, mentor: Roger Pack</h4>
+
+ <p>
+ Mate was working on directshow input from digital video sources. He
+ got working input from ATSC input sources, with specifiable tuner.
+ </p>
+
+ <p>
+ The code has not been committed, but a patch of it was sent to the
+ ffmpeg-devel mailing list for future use.
+ </p>
+
+ <p>
+ The mentor plans on cleaning it up and committing it, at least for the
+ ATSC side of things. Mate and the mentor are still working trying to
+ finally figure out how to get DVB working.
+ </p>
+
+ <h4>Implementing full support for 3GPP Timed Text Subtitles, mentee: Niklesh Lalwani, mentor: Philip Langdale</h4>
+
+ <p>
+ Niklesh's project was to expand our support for 3GPP Timed Text
+ subtitles. This is the native subtitle format for mp4 containers, and
+ is interesting because it's usually the only subtitle format supported
+ by the stock playback applications on iOS and Android devices.
+ </p>
+
+ <p>
+ ffmpeg already had basic support for these subtitles which ignored all
+ formatting information - it just provided basic plain-text support.
+ </p>
+
+ <p>
+ Niklesh did work to add support on both the encode and decode side for
+ text formatting capabilities, such as font size/colour and effects like
+ bold/italics, highlighting, etc.
+ </p>
+
+ <p>
+ The main challenge here is that Timed Text handles formatting in a very
+ different way from most common subtitle formats. It uses a binary
+ encoding (based on mp4 boxes, naturally) and stores information
+ separately from the text itself. This requires additional work to track
+ which parts of the text formatting applies to, and explicitly dealing
+ with overlapping formatting (which other formats support but Timed
+ Text does not) so it requires breaking the overlapping sections into
+ separate non-overlapping ones with different formatting.
+ </p>
+
+ <p>
+ Finally, Niklesh had to be careful about not trusting any size
+ information in the subtitles - and that's no joke: the now infamous
+ Android stagefright bug was in code for parsing Timed Text subtitles.
+ </p>
+
+ <p>
+ All of Niklesh's work is committed and was released in ffmpeg 2.8.
+ </p>
+
+<h4>libswscale refactoring, mentee: Pedro Arthur, mentors: Michael Niedermayer, Ramiro Polla</h4>
+
+ <p>
+ Pedro Arthur has modularized the vertical and horizontal scalers.
+ To do this he designed and implemented a generic filter framework
+ and moved the existing scaler code into it. These changes now allow
+ easily adding removing, splitting or merging processing steps.
+ The implementation was benchmarked and several alternatives were
+ tried to avoid speedloss.
+ </p>
+
+ <p>
+ He also added gamma corrected scaling support.
+ An example to use gamma corrected scaling would be:
+ <pre>
+ ffmpeg -i input -vf scale=512:384:gamma=1 output
+ </pre>
+ </p>
+
+ <p>
+ Pedro has done impressive work considering the short time available,
+ and he is a FFmpeg committer now. He continues to contribute to
+ FFmpeg, and has fixed some bugs in libswscale after GSoC has
+ ended.
+ </p>
+
+ <h4>AAC Encoder Improvements, mentee: Rostislav Pehlivanov, mentor: Claudio Freire</h4>
+
+ <p>
+ Rostislav Pehlivanov has implemented PNS, TNS, I/S coding and main
+ prediction on the native AAC encoder. Of all those extensions, only
+ TNS was left in a less-than-usable state, but the implementation has
+ been pushed (disabled) anyway since it's a good basis for further
+ improvements.
+ </p>
+
+ <p>
+ PNS replaces noisy bands with a single scalefactor representing the
+ energy of that band, gaining in coding efficiency considerably, and
+ the quality improvements on low bitrates are impressive for such a
+ simple feature.
+ </p>
+
+ <p>
+ TNS still needs some polishing, but has the potential to reduce coding
+ artifacts by applying noise shaping in the temporal domain (something
+ that is a source of annoying, notable distortion on low-entropy
+ bands).
+ </p>
+
+ <p>
+ Intensity Stereo coding (I/S) can double coding efficiency by
+ exploiting strong correlation between stereo channels, most effective
+ on pop-style tracks that employ panned mixing. The technique is not as
+ effective on classic X-Y recordings though.
+ </p>
+
+ <p>
+ Finally, main prediction improves coding efficiency by exploiting
+ correlation among successive frames. While the gains have not been
+ huge at this point, Rostislav has remained active even after the GSoC,
+ and is polishing both TNS and main prediction, as well as looking for
+ further improvements to make.
+ </p>
+
+ <p>
+ In the process, the MIPS port of the encoder was broken a few times,
+ something he's also working to fix.
+ </p>
+
+ <h4>Animated Portable Network Graphics (APNG), mentee: Donny Yang, mentor: Paul B Mahol</h4>
+
+ <p>
+ Donny Yang implemented basic keyframe only APNG encoder as the
+ qualification task. Later he wrote interframe compression via
+ various blend modes. The current implementation tries all blend
+ modes and picks one which takes the smallest amount of memory.
+ </p>
+
+ <p>
+ Special care was taken to make sure that the decoder plays
+ correctly all files found in the wild and that the encoder
+ produces files that can be played in browsers that support APNG.
+ </p>
+
+ <p>
+ During his work he was tasked to fix any encountered bug in the
+ decoder due to the fact that it doesn't match APNG
+ specifications. Thanks to this work, a long standing bug in the
+ PNG decoder has been fixed.
+ </p>
+
+ <p>
+ For latter work he plans to continue working on the encoder,
+ making it possible to select which blend modes will be used in the
+ encoding process. This could speed up encoding of APNG files.
+ </p>
+
<a id="pr2.8"></a><h3>September 9th, 2015, FFmpeg 2.8</h3>
<p>
We published release <b><a href="download.html#release_2.8">2.8</a></b> as new major version.
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Summary of changes:
src/index | 234 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 234 insertions(+)
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