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

Vitor Sessak vitor1001
Sun Sep 14 17:55:16 CEST 2008


Michael Niedermayer wrote:
> On Sat, Sep 13, 2008 at 09:48:46PM +0200, Vitor Sessak wrote:
>> Michael Niedermayer wrote:
>>> On Sat, Sep 13, 2008 at 07:07:26PM +0200, Vitor Sessak wrote:
>>>> Michael Niedermayer wrote:
>>>>> On Fri, Sep 05, 2008 at 12:23:58AM +0200, Vitor Sessak wrote:
>>>>>> Vitor Sessak wrote:
>>> [...]
>>>>> [...]
>>>>>> static void colmult(float *tgt, const float *m1, const float *m2, int n)
>>>>>> {
>>>>>>     while (n--)
>>>>>>         *tgt++ = *m1++ * *m2++;
>>>>>> }
>>>>> such function is commonly called apply_window() in other codecs
>>>>>> static void decode(RA288Context *ractx, float gain, int cb_coef)
>>>>>> {
>>>>>>     int i, j;
>>>>>>     double sumsum;
>>>>>>     float sum, buffer[5];
>>>>>>     float *block = ractx->sp_block + 36; // Current block
>>>>>>
>>>>>>     memmove(ractx->sp_block, ractx->sp_block + 5, 
>>>>>> 36*sizeof(*ractx->sp_block));
>>>>>>
>>>>>>     for (i=0; i < 5; i++) {
>>>>>>         block[i] = 0.;
>>>>>>         for (j=0; j < 36; j++)
>>>>>>             block[i] -= block[i-1-j]*ractx->sp_lpc[j];
>>>>>>     }
>>>>>>
>>>>>>     /* block 46 of G.728 spec */
>>>>>>     sum = 32.;
>>>>>>     for (i=0; i < 10; i++)
>>>>>>         sum -= ractx->gain_block[9-i] * ractx->gain_lpc[i];
>>>>>>
>>>>>>     /* block 47 of G.728 spec */
>>>>>>     sum = av_clipf(sum, 0, 60);
>>>>>>
>>>>>>     /* block 48 of G.728 spec */
>>>>>>     sumsum = exp(sum * 0.1151292546497) * gain; /* pow(10.0,sum/20)*gain 
>>>>>> */
>>>>>>
>>>>>>     for (i=0; i < 5; i++)
>>>>>>         buffer[i] = codetable[cb_coef][i] * sumsum;
>>>>>>
>>>>>>     sum = scalar_product_float(buffer, buffer, 5) / 5;
>>>>>>
>>>>>>     sum = FFMAX(sum, 1);
>>>>>>
>>>>>>     /* shift and store */
>>>>>>     memmove(ractx->gain_block, ractx->gain_block + 1,
>>>>>>             9 * sizeof(*ractx->gain_block));
>>>>>>
>>>>>>     ractx->gain_block[9] = 10 * log10(sum) - 32;
>>>>>>
>>>>>>     for (i=1; i < 5; i++)
>>>>>>         for (j=i-1; j >= 0; j--)
>>>>>>             buffer[i] -= ractx->sp_lpc[i-j-1] * buffer[j];
>>>>>>
>>>>>>     /* output */
>>>>>>     for (i=0; i < 5; i++)
>>>>>>         block[i] = av_clipf(block[i] + buffer[i], -4095, 4095);
>>>>> can the buffer values be stored in block and sp_lpc applied over both
>>>>> in one pass instead of this 2 pass and add-clip thing?
>>>> I can't apply sp_lpc to buffer+block, so I need two buffers...
>>> What i was thinking about was:
>>>
>>>     /* block 46 of G.728 spec */
>>>     sum = 32.;
>>>     for (i=0; i < 10; i++)
>>>         sum -= gain_block[9-i] * ractx->gain_lpc[i];
>>>
>>>     /* block 47 of G.728 spec */
>>>     sum = av_clipf(sum, 0, 60);
>>>
>>>     /* block 48 of G.728 spec */
>>>     sumsum = exp(sum * 0.1151292546497) * gain; /* pow(10.0,sum/20)*gain */
>>>
>>>     for (i=0; i < 5; i++)
>>>         buffer[i] = codetable[cb_coef][i] * sumsum * (1./2048.);
>>>
>>>     sum = scalar_product_float(buffer, buffer, 5) / 5;
>>>
>>>     sum = FFMAX(sum, 1);
>>>
>>>     /* shift and store */
>>>     memmove(gain_block, gain_block + 1, 9 * sizeof(*gain_block));
>>>
>>>     gain_block[9] = 10 * log10(sum) - 32;
>>>
>>>     for (i=0; i < 5; i++) {
>>>         block[i] = buffer[i];
>> Here you are overwriting the value of block[i] (while previous code used 
>> this value).
> 
> previous code did:
> for (i=0; i < 5; i++) {
>     block[i] = 0.;
> 
> so that certainly was not useing it

Ok, the problem is the following. Now we have (moving down a few loops):

     for (i=1; i < 5; i++)
         for (j=i-1; j >= 0; j--)
             buffer[i] -= ractx->sp_lpc[i-j-1] * buffer[j];

     for (i=0; i < 5; i++) {
         block[i] = 0.;
         for (j=0; j < 36; j++)
             block[i] -= block[i-1-j]*ractx->sp_lpc[j];
     }

     /* output */
     for (i=0; i < 5; i++)
         block[i] = av_clipf(block[i] + buffer[i], -4095, 4095);

And I cannot change block[i] = 0. to block[i] = buffer[i] because 
block[0] will be read for evaluating block[1] in the second loop.

>>>>> [...]
>>>>>> 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/ .

-Vitor




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