[Vorbis-dev] Lost residue modifications

[Jesús Díaz Vico]

Hm... and I'm working on the 1.2.3 libvorbis release. The line number
reference might be useless with that info :)

Jesús Díaz Vico escribió:
> Hello,
> 
> I'm trying to modify the residue vectors in Vorbis audio files at
> encoding time. For testing, I'm just adding +1 to each residue vector's
> element, so e.g., if I have an original residue vector of [0,1,2,3] I
> modify it during the encoding to be [1,2,3,4], and at the decoder's side
> I should receive the [1,2,3,4] vector. The problem is that, after adding
> the +1, I still receive the vector [0,1,2,3].
> 
> I'm making this +1 to each element in a simple for loop for each
> channel, immediatly before the line number 700 of mapping0.c (just
> before calling _vp_couple):
> 
> for(count=0; count<psy_look->n; count++) {
>   vb->pcm[i][count] += 1;
> }
> 
> Obviously, there is some place after in the code where my changes are
> being overwritten or somehow discarded, but I am being unable to find it
> (I thought it would be where a comment line says "couple_bundle is
> destructively overwritten by the class function if some but not all of
> the channels are marked as silence; build a fresh copy", but there is no
> silence in any channel).
> 
> Could someone give me a hint on what may be happening, where my changes
> are being lost or where should I modify the residual vectors... anything.
> 
> Thank you.
> 
> PS: If it is important, I'm using quality level 6+ to force lossless
> coupling (AFAIK, 6+ quality levels are the ones with lossless coupling,
> right?).
>