[FFmpeg-devel] ffvorbis, inverted output

[Benjamin Larsson]

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.

MvH
Benjamin Larsson