[FFmpeg-devel] Using dsp.fdct()

Michael Niedermayer michaelni
Sat Apr 19 05:01:50 CEST 2008

On Sat, Apr 19, 2008 at 03:25:44AM +0100, Ramiro Polla wrote:
> Hello,
> While writing the mimic decoder, iive taught me that to use 
> dsp.idct_xxx() functions, I had to create a scantable such as:
> init() {
>      ff_init_scantable(ctx->dsp.idct_permutation, &ctx->table, zig_zag);
> }
> decode() {
>      while(coeffs)
>          block[ctx->table.permutated[pos]] = coeff;
>      ctx->dsp.idct(block);
> }
> Now, with dsp.fdct(), do I also have to use a scantable?

I think not but its late and iam tired so who knows :)

But you do have to permute between fdct and idct if you run a idct over
the output. (hint: ff_block_permute())

PS: yes you do need to run a idct over it if you want to use it as reference
frame otherwise decoder and encoder will have different reference frames.

Ohh and thanks for working on a mimic encoder .. i do guess correct dont i? :)


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Asymptotically faster algorithms should always be preferred if you have
asymptotical amounts of data
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