[FFmpeg-devel] ffvorbis, inverted output

Benjamin Larsson banan
Sun Sep 14 21:16:06 CEST 2008

Siarhei Siamashka wrote:
> Hi,
> I tried to do PSNR comparison of libvorbis/ffvorbis/tremor and noticed that
> output from ffvorbis is actually inverted (ex. output 0xFFFF in libvorbis
> corresponds to 0x0001 in ffvorbis and so on) when compared to the output 
> from the other decoders.
> Should this be fixed? If yes, what would be the right solution?
> Probably just the sign of values in tables in 'vorbis_data.c' could 
> be changed.

I think this comes from the mdct, to correct this just negate some scale
factor or the overlap window.

Benjamin Larsson

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