[FFmpeg-devel] [RFC] Implementation of closed caption support

Reimar Döffinger Reimar.Doeffinger at gmx.de
Mon Aug 4 21:58:58 CEST 2014

On Mon, Aug 04, 2014 at 09:35:02PM +0200, Gisle Sælensminde wrote:
> Bitstream filter:
> Pro:
> - Modular, the CC code can be kept separate.
> - Less complex code
> Cons:
> Need for features that I can't see is present in the bitstream filters:
> - As far as I can see -no support for timestamps (PTS), required for
> reordering and timestams in the output file
> - No support for  arguments to bitstream filters (unlike audio and video
> filters)
> Decoder:
> Pro:
> - Parser already present. Easy to insert extraction code on the right spots
> Cons:
> - Less modular, CC code mixed with decoding code.
> - Does not easily extend to encoders/insertion.
> - Parameters (for input files)?

*scratches head* I wonder now if you misunderstood or if you discarded
the variant I pointed out due to effort/complexity?

- Parsing is often done in demuxer anyway
- Appears as proper subtitle stream
- Same usage whether you want to mux into/demux from MPEG-TS or formats
  saving CC data separately like MOV and WTV
- Works without requiring decode/encode

- Needs reordering code in demuxer/parser
- Needs extra signalling code from parser to demuxer (probably)
- Custom code for partially rewriting frames in the muxer needed for
  MPEG containers
- Generally a good bit more of complexity.

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