[FFmpeg-devel] [PATCH] ffmpeg/web/index: add news describing GSoC 2015 program outcome
Stefano Sabatini
stefasab at gmail.com
Sun Sep 27 17:56:38 CEST 2015
On date Sunday 2015-09-27 09:44:33 -0400, Ganesh Ajjanagadde encoded:
> On Sun, Sep 27, 2015 at 8:37 AM, Stefano Sabatini <stefasab at gmail.com> wrote:
> > ---
> > src/index | 234 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 234 insertions(+)
[...]
> > + <p>
> > + During the program he extended the API with possibility to remove and
> > + rename files on remote servers. He implemented/finished the
> > + implementation of these features for file, Samba, SFTP, and FTP
> > + protocols.
> > + </p>
>
> nit: with possiblity -> with the possibility
>
> implemented/finished: is the vagueness necessary because some of these
> were completed and others not? Otherwise, I prefer the more explicit
> "implemented and finished".
Changed to: finished the implementation (since "implement the
implementations" sounds ugly/redundant).
>
> > +
> > + <p>
> > + At the end of the program, Mariusz provided a sketch of 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 up, 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>
>
> committing up - never heard this usage, perhaps "committing it" or
> even a simple "committing"?
=> committing it
[...]
> > +<h4>libswscale refactoring, mentee: Pedro Arthur, mentors: Michael Niedermayer, Ramiro Polla</h4>
> > +
> > + <p>
> > + Pedro Arthur has modlularized 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 where
> > + tried to avoid speedloss.
> > + </p>
>
> modl.. -> modularized
> where tried -> were tried
>
> > +
> > + <p>
> > + He also added gamma correct scaling support.
> > + An example to use gamma corrected scaling would be:
> > + <pre>
> > + ffmpeg -i input -vf scale=512:384:gamma=1 output
> > + </pre>
> > + </p>
>
> gamma correct scaling -> gamma corrected scaling
>
> > +
> > + <p>
> > + Pedro has done impressive work considering the short time available,
> > + and he is a FFmpeg comitter now. He continues to contribute to
> > + FFmpeg, and has fixed some bugs in libswscale after GSoC has
> > + ended.
> > + </p>
>
> comitter -> committer
>
> > +
> > + <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
> > + furhter improvements to make.
> > + </p>
>
> furhter -> further
>
> > +
> > + <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 qualification
> > + task, later he wrote kind of interframe compression via various blend
> > + modes. Current implementation tries all blend modes and picks one which
> > + takes the smallest amount of memory.
> > + </p>
>
> as qualification -> "as the qualification" or "as a qualification"
> depending on whether the qualification task is unique.
changed to: as the qualification
> change the , before later to a ; (or IMO a . with a fresh sentence)
> wrote kind of -> vague, ambiguous between "kind of wrote" and "wrote a
> type of". I think you wanted a "wrote a type of".
removed the "kind of" to the simpler "he wrote interframe compression
..."
> Current implementation -> The current implementation
>
> > +
> > + <p>
> > + Special care was taken to make sure that the decoder plays correctly
> > + all files found in wild and that the encoder produces files that can
> > + be played in browsers that support APNG.
> > + </p>
>
> found in wild -> found in the wild
>
> > +
> > + <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, the also long standing bug in the
> > + PNG decoder has been fixed.
> > + </p>
>
> Maybe reference the trac ticket number?
> the also long standing bug -> "a long standing bug" is simpler and
> conveys the same thing
opted for "a long standing bug .. has been fixed".
> > +
> > + <p>
> > + For latter work he plans to continue working on the encoder, making
> > + possible to select which blend modes will be used in the encoding
> > + process, which could speed up encoding of APNG files.
> > + </p>
>
> making possible -> making it possible
> remove the , add a . and say "This could speed up encoding of APNG files."
Yeah.
[...]
Thanks for the detailed review, updated version attached.
--
FFmpeg = Free and Fierce Multipurpose Patchable Eretic Governor
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