[FFmpeg-devel] GSoC 2016 own ideas

Paul B Mahol onemda at gmail.com
Thu Feb 18 18:53:45 CET 2016


Dana 18. 2. 2016. 18:27 osoba "Gerion Entrup" <gerion.entrup.ffdev at flump.de>
napisala je:
>
> Good day,
>
> I'm a master student and long term FFmpeg-user. I want to participate in
the GSoC 2016 for FFmpeg. The reason, I write this, is that I want to
suggest some own ideas. It could be, that some of the mentioned things are
wrong (because FFmpeg could do this already or it it much more difficult
than I think). Please correct me if so.
> I'm excited to hear, what do you think about this ideas, if you think,
they are suitable for GSoC and if you maybe are willing to mentor some of
this.
>
> 1. *disc support
>
> What current FFmpeg could do:
> - Bluray support through protocol support with prefix "bluray:" and
libbluray. The implemention is some kind of limited. There is missing
chapter support. The "main movie" selection is simply the longest one.
Menus are not supported. Afaik no metadata are transfered.
> - CD support through libavdevice and libcdio. Last time I tried it, it
only works under some strange circumstances (I have to set the parameter
"-ss 0"). I don't know if it is fixed right now. It recognizes a CD as one
track with multiple chapters. Afaik CD-Text is not supported.
> - No DVD support at all. I saw, that Stefano ones write a patch [1]
(protocol and libdvdnav based), which seems to work in principal, but was
probably not ready to merge.
>
> Goal:
> - Implement an uniform solution for *disc support, that also support
metadata.
> - Maybe (?): Add some kind of Menu Support, FFmpeg is not made for this
atm, I think. Not sure how difficult it is.
> - Maybe (?): Try to change something on libdvdnav/libdvdread to make it
more consistent (to libbluray ?). Similar idea from Flameeyes [2].
>
> Qualification task:
> - Maybe (?): Add chapter support for the current Bluray implementation
(get the chapters out of libbluray is fairly simple, I'm not sure how
difficult it is to get them into the stream).
>
> Comments:
> - I would try to orientate on VLC, mplayer and mpv implementation.
> - libdvdread/nav seem to do much less than libbluray, so the main work
would be the dvd support, I guess.
> - All kinds of discs normally contains more than one track. My idea for a
solution would be, that ffmpeg recognize the disc as multiinput and choose
the mainmovie as default.
>

This is out of scope for project. And who will use it when everyone have
own solution.

>
> 2. treelike metadata
>
> What current FFmpeg could do:
> - Metadata is always an AVDictionary (string based afaik).
> - Some metadata systems like the one of Matroska use a treelike structure
(xml in mkv), so you can specify the charatername given an actor or define
more than on actor, see example at the end of the mail.
>
> Goal:
> Rewrite the FFmpeg metadata system, to support extended tags. In Detail:
> - Support for more than one value per key.
> - Support for more key/value pairs as value.
>
> Qualification task:
> No idea.
>
> Comments:
> Not sure, if this task is GSoC suitable.

Trivial and out of scope.

>
>
> 3. Vector graphic support
>
> What current FFmpeg could do:
> - No support at all, afaik.
>
> Goal:
> - Extend FFmpeg to support vector graphics (without converting to pixel
graphics).
> - Write an SVG decoder for this.
> - Write an vector to pixel image converter/filter.
>
> Qualification task:
> No idea.
>
> Comments:
> I think, this could be a very hard task. Could you comment, whether you
find this suitable? I have no experience with SVG. Maybe it could be based
on cairo.

Out of scope.

>
>
> 4. Usable analyse filter output for programs
> Not sure, if this is a real problem at all. Not sure if this is suitable
for GSoC at all.
>
> What current FFmpeg could do:
> - Receive (multiple) streams in filter and write back other streams.
> - The problem I see here, is that the output of analyse filters is hard
to process (needs some kind of subprocess and extended usage of grep/sed).
>     Examples: All filters that analyse some thing and then "print" it to
stdout, like cropdetect, volumedetect, blackframe, .... Some (not
implemented filter) like tonality, bpm detection, waveform analysis, ...
>
> Goal:
> - Rewrite the filtersystem, so that some function "receive_output"
exists, that could be called from the external API or another filter to get
non multimedia data as the filter output, like an String for tonality, or
an index array for the wavform, etc.
>
> Comments:
> - Has the side effect, that a following filter in the chain could use the
output to do some other stuff.
> - Not sure, how hard (and wanted) this is.

Already available via metadata.

>
>
>
> Other ideas, but imho not suitable for GSoC:
> - Jack output support (too simple for GSoC)
> - Python bindings
> - merge of ffmpeg and ffplay (call ffmpeg without output reacts like
ffplay). Maybe this idea is fairly naive.
>
> thank you,
> Gerion
>
> [1]
https://gitorious.org/ffmpeg/sastes-ffmpeg/commit/716c1f7b2ad02a906ad1e47182492554b668f3dc?p=ffmpeg:sastes-ffmpeg.git;a=blob;f=libavformat/dvdproto.c;h=72ed431c6a47c87e30e4876587c6bb97215517cf;hb=4ed59d83a6e9fb45c3134bb67267e9b05927125c
> [2] https://blog.flameeyes.eu/2013/02/it-s-that-time-of-the-year-again
>
> example tags from matroska:
>     ...
>     <Simple>
>       <Name>ACTOR</Name>
>       <String>Matthew McConaughey</String>
>       <TagLanguage>und</TagLanguage>
>       <DefaultLanguage>1</DefaultLanguage>
>       <Simple>
>         <Name>CHARACTER</Name>
>         <String>Jake Tyler Brigance</String>
>         <TagLanguage>und</TagLanguage>
>         <DefaultLanguage>1</DefaultLanguage>
>       </Simple>
>     </Simple>
>     <Simple>
>       <Name>ACTOR</Name>
>       <String>Sandra Bullock</String>
>       <TagLanguage>und</TagLanguage>
>       <DefaultLanguage>1</DefaultLanguage>
>       <Simple>
>         <Name>CHARACTER</Name>
>         <String>Ellen Roark</String>
>         <TagLanguage>und</TagLanguage>
>         <DefaultLanguage>1</DefaultLanguage>
>       </Simple>
>     </Simple>
>     ...
>
>
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