[Ffmpeg-devel] ReplayGain for Vorbis decoder

[Balatoni Denes]

Hi!

I too think it need not be supported in the decoder itself. 

The pros would be:
- decoding+applying replaygain maybe 5 % faster if optmized than applying 
replygain affter decoding
- maybe slightly better quality (whether it is audible should be ABXed ;) )

cons:
- difficult to pass the value to the decoder (unless the comment header is 
parsed, that is right now redundant in the extradata)
- somewhat more memory and initaliztaion time needed if optimized
- needs to be implemented (in the window overlap/add part I guess) by someone

But if it's such a usefull function I will not stop anybody from implementing 
it in the decoder.

bye
Denes

2005. m?jus 19. 12.39-kor Milan Cutka ezeket a bolcs gondolatokat fogalmazta 
meg:
> > castet.matthieu at free.fr writes:
> >> Selon Milan Cutka <milan_cutka at yahoo.com>:
> >>> I'm adding VorbisGain tag support to Vorbis decoder. It requires
> >>> parsing of comments header which I implemented already. Right now
> >>> I'm deciding whether to directly multiply decoded samples in
> >>> vorbis_decode_frame or add new field to AVCodecContext, fill it
> >>> with found multiplier and let the application to perform the
> >>> multiplication. I'd like to know your opinions. Thanks.
> >>
> >> Well it is quite ugly to pass option to vorbis decoder via comment which
> >> are normaly decoded in ogg demuxer...
> >
> > I agree.  A better idea might be to have the demuxer fill in some
> > field in an appropriate place, and let the application deal with it.
> > ID3v2 tags can have similar things in them, if we'll ever support
> > those.
>
> When using libavcodec vorbis decoder in ffdshow I have to parse comment on
> my own, because I don't get information such as replaygain from demuxer. Of
> course I could parse the headers in my application and don't put it to
> libavcodec, but I guess it could be useful for other applications using
> libavcodec but not libavformat. And in my opinion replaygain is different
> from other comments like author, song name,... because it directly affects
> playback.
>
>   Milan

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