[FFmpeg-devel] [PATCHv5 4/4] lavc: add teletext decoder using libzvbi

Carl Eugen Hoyos cehoyos at ag.or.at
Sat Aug 24 22:57:54 CEST 2013

Marton Balint <cus <at> passwd.hu> writes:

> > Or in other words: Is one FFmpeg subtitle
> > stream provided for all pages plus one
> > stream for each subtitle page?
> >
> > Or is this not a good idea?
> At the moment, a single subtitle stream is provided for 
> all the teletext packets, and the decoder decides which 
> pages to decode from these teletext packets.

Meaning you cannot decode / reencode two teletext subtitle 
pages at the same time, or do I misunderstand?

> Creating separate streams in the demuxer for each entry 
> in the teletext descriptor may have it's advantages, but 
> I can't think of a way to split the teletext packets to 
> multiple streams without decoding the whole teletext in 
> the demuxer first.

(Doesn't this sentence indicate that this should be solved 
before the patch gets applied?)

> Also I don't know if the mpegts demuxer will like if we 
> just start adding streams with the same PID values...

I believe this is done with TrueHD / AC-3 streams.

> The only way I see is if we pass all teletext packets to 
> all these streams, and as a packet side data also pass a 
> default page filter to the decoder, but I don't know if 
> that is something we should do...
> Anyway, since we definitely need a stream with all the 
> teletext packets, these extra subtitle streams can be 
> added later :P

Of course!

Thank you for the explanations, Carl Eugen

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