[FFmpeg-devel] Review request - ra288.{c,h} ra144.{c,h}

[Michael Niedermayer]

On Sun, Sep 14, 2008 at 08:17:18PM +0200, Vitor Sessak wrote:
> Michael Niedermayer wrote:
> > On Sun, Sep 14, 2008 at 05:55:16PM +0200, Vitor Sessak wrote:
[...]
> >>>>>>> [...]
> >>>>>>>> static int ra288_decode_frame(AVCodecContext * avctx, void *data,
> >>>>>>>>                               int *data_size, const uint8_t * buf,
> >>>>>>>>                               int buf_size)
> >>>>>>>> {
> >>>>>>>>     int16_t *out = data;
> >>>>>>>>     int i, j;
> >>>>>>>>     RA288Context *ractx = avctx->priv_data;
> >>>>>>>>     GetBitContext gb;
> >>>>>>>>
> >>>>>>>>     if (buf_size < avctx->block_align) {
> >>>>>>>>         av_log(avctx, AV_LOG_ERROR,
> >>>>>>>>                "Error! Input buffer is too small [%d<%d]\n",
> >>>>>>>>                buf_size, avctx->block_align);
> >>>>>>>>         return 0;
> >>>>>>>>     }
> >>>>>>>>
> >>>>>>>>     if (*data_size < 32*5*2)
> >>>>>>>>         return -1;
> >>>>>>>>
> >>>>>>>>     init_get_bits(&gb, buf, avctx->block_align * 8);
> >>>>>>>>
> >>>>>>>>     for (i=0; i < 32; i++) {
> >>>>>>>>         float gain = amptable[get_bits(&gb, 3)];
> >>>>>>>>         int cb_coef = get_bits(&gb, 6 + (i&1));
> >>>>>>>>
> >>>>>>>>         decode(ractx, gain, cb_coef);
> >>>>>>>>
> >>>>>>>>         for (j=0; j < 5; j++)
> >>>>>>>>             *(out++) = 8 * ractx->sp_block[36 + j];
> >>>>>>> if float output works already, then this could output floats, if not then
> >>>>>>> this could use lrintf()
> >>>>>> I've tried the float output (with the attached patch) and it didn't work. 
> >>>>> ok
> >>>>>
> >>>>>
> >>>>>> Using lrint() changes slightly the output (PSNR about 99), is it expected?
> >>>>> yes, it does round differently (=more correctly)
> >>>> Too correct maybe. PSNR to binary decoder with SVN:
> >>>>
> >>>> stddev:    0.15 PSNR:112.70 bytes:   990720/  1013760
> >>>> stddev:    0.04 PSNR:122.74 bytes:   368640/   368640
> >>>> stddev:    0.07 PSNR:118.84 bytes:   460800/   458752
> >>>> stddev:    0.31 PSNR:106.24 bytes:  6451200/  6451200
> >>>>
> >>>> Using lrint()
> >>>>
> >>>> stddev:    0.70 PSNR: 99.33 bytes:   990720/  1013760
> >>>> stddev:    0.70 PSNR: 99.35 bytes:   368640/   368640
> >>>> stddev:    0.70 PSNR: 99.35 bytes:   460800/   458752
> >>>> stddev:    0.75 PSNR: 98.76 bytes:  6451200/  6451200
> >>> yes, the rounding is more accurate, and differs by +-1 50% of the time from
> >>> the binary decoder, sqrt(0.5) ~ 0.7
> >>>
> >>> If you want a proof that it is better, you should compare the original
> >>> pcm that is
> >>>
> >>> X -> encoder -> binary decoder -> Y
> >>>              -> FF decoder ->Z
> >>>
> >>> and look at how the X-Y and X-Z change relative to each other.
> >>>
> >>> Also you would see a similar PSNR change relative to the binary decoder if
> >>> you would output floats.
> >> I've already tried comparing PSNR to the original input when I was 
> >> looking for a way to test float codecs in FATE.
> >>
> >> vitor at vitor$ ffmpeg -i luckynightmono2.ra -ac 1 -ar 8000 test.wav
> >> vitor at vitor$ ffmpeg -i luckynight.wav -ac 1 -ar 8000 test2.wav
> >> vitor at vitor$ tiny_psnr test.wav test2.wav 2 0 44
> >> stddev: 5981.39 PSNR: 20.78 bytes:   990720/   967662
> >> vitor at vitor$ tiny_psnr test.wav test2.wav 2 2 44
> >> stddev: 5982.77 PSNR: 20.78 bytes:   990718/   967662
> >> vitor at vitor$ tiny_psnr test.wav test2.wav 2 100 44
> >> stddev: 6012.76 PSNR: 20.74 bytes:   990620/   967662
> >>
> >> And by looking at results, if I change the "skip bytes" parameter I 
> >> don't get much change in PSNR. For me, this is a signal that the value I 
> >> got is meaningless (since it don't change a lot if I compare it with 
> >> different data). I asked about it in IRC and people told me that PSNR 
> >> didn't worked very well to LPC vocoders. Sample in 
> >> http://samples.mplayerhq.hu/real/AC-28_8/ .
> > 
> > considering that the claimed encoder input has
> > 10668716 bytes of 44.1khz at stereo
> > and that /2/44100*8000 is ~967684
> > and the ra288 decoder output has 990764 bytes i cant help but wonder
> > why, but of course this is incompareable. PSNR or otherwise
> 
> Yes, the files have different sizes. That's why I started poking with 
> "skip bytes" and tried to cut the files. But I didn't succeeded in 
> making they match whatever I did.

how has the .ra file been generated?
what happens with a 2x as long input file? does the size difference
stay constant or grow?

what does the binary decoder produce for it? is that also too big?

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Republics decline into democracies and democracies degenerate into
despotisms. -- Aristotle
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