[FFmpeg-devel] GSoC 2016 own ideas

[Gerion Entrup]

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.


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.


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.


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.



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>
    ...