[FFmpeg-devel] 4xm idct computation

[yann.lepetitcorps at free.fr]

Selon yann.lepetitcorps at free.fr:

> Selon yann.lepetitcorps at free.fr:
>
> > Hi,
> >
> > I have take a look into the libavcodec/4xm.c
> > => can the IDCT to be remplaced by something more simpler like Haar
> wavelets
> > ?
> > (for to can be accellerated by MMX instructions for example)
> >
> >
> > @+
> > Yannoo
> > _______________________________________________
> > ffmpeg-devel mailing list
> > ffmpeg-devel at ffmpeg.org
> > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> >
>
> More precisely, I search an encoder/decoder that work like the DCT/iDCT but
> with
> the De Haar, Debauchies and/or others lifting schemes transforms instead the
> [Fast] Fourrier Transform
>
> @+
> Yannoo
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>

I have found this line in libavcodec/4xm.c

  DCTELEM *temp= block[(x>>2) + 2*(y>>2)] + 2*(x&3) + 2*8*(y&3); //FIXME
optimize

=> this can perhaps to be optimised by the use of two block_tab[x][y] arrays  ?
    (cf. DCTELEM *temp = block[ block_tab1[x][y] ] + bloc_tab2[x&3][y&3]; )

@+
Yannoo