[FFmpeg-devel] [PATCH] QCELP decoder
Kenan Gillet
kenan.gillet
Fri Nov 21 02:51:22 CET 2008
Hi,
On Nov 20, 2008, at 5:08 PM, Michael Niedermayer wrote:
>>>
>>>
>>> [...]
>>>> +/**
>>>> + * Computes the Pa or Qa coefficients needed for LSP to LPC
>>>> conversion.
>>>> + * We only need to calculate the 6 first elements of the
>>>> polynomial.
>>>> + *
>>>> + * @param lspf line spectral pair frequencies
>>>> + * @param v_poly polynomial input/output as a vector
>>>> + *
>>>> + * TIA/EIA/IS-733 2.4.3.3.5-1/2
>>>> + */
>>>> +static void lsp2poly(const float *lspf,
>>>> + float *v_poly) {
>>>> + float val, *v;
>>>> + int i;
>>>> +
>>>> + // optimization to simplify calculation in loop
>>>> + v_poly++;
>>>> +
>>>> + for (i = 0; i < 10; i += 2) {
>>>> + val = -2 * cos(M_PI * *lspf);
>>>> + lspf += 2;
>>>> + v = v_poly + FFMIN(4, i);
>>>> +
>>>> + if (i < 4) {
>>>> + v[2] = v[0];
>>>> + v[1] = v[0] * val + v[-1];
>>>> + }
>>>> + for ( ; v > v_poly; v--)
>>>> + v[0] = v[0]
>>>> + + v[-1] * val
>>>> + + v[-2];
>>>> + v[0] += v[-1] * val;
>>>> + }
>>>> +}
>>>> +
>>>> +/**
>>>> + * Reconstructs LPC coefficients from the line spectral pair
>>>> frequencies
>>>> + * and performs bandwidth expansion.
>>>> + *
>>>> + * @param lspf line spectral pair frequencies
>>>> + * @param lpc linear predictive coding coefficients
>>>> + *
>>>> + * @note: bandwith_expansion_coeff could be precalculated into a
>>>> table
>>>> + * but it seems to be slower on x86
>>>> + *
>>>> + * TIA/EIA/IS-733 2.4.3.3.5
>>>> + */
>>>> +void qcelp_lspf2lpc(const float *lspf,
>>>> + float *lpc) {
>>>> + float pa[6], qa[6];
>>>> + int i;
>>>> + float bandwith_expansion_coeff = -
>>>> QCELP_BANDWITH_EXPANSION_COEFF;
>>>> +
>>>
>>>> + pa[0] = 0.5;
>>>> + pa[1] = 0.5;
>>>> + lsp2poly(lspf, pa);
>>>> +
>>>> + qa[0] = 0.5;
>>>> + qa[1] = -0.5;
>>>> + lsp2poly(lspf + 1, qa);
>>>
>>> it should be faster to deal with 0.5 + 0.5x / 0.5 - 0.5x after
>>> building
>>> the polynomials
>>
>> done
>>
>>
>>>
>>> anyway, see ff_acelp_lsp2lpc
>>
>> done, it is globally ~10% faster.
>>
>> but it gives some significant difference in the WAV output.
>> I doule check, and it seems to come from the float rounding :(
>> here is the list of result of 'tiny_psnr old.wav new.wav'.
>
> what happens with double instead of float?
with keeping the signature of qcelp_lspf2lpc(float *, float *)
and changing all the calculation into double for
the code before and after optimization:
101.mov: audio mismatchs from previous build
stddev: 0.02 PSNR: 78.92 bytes: 250284/ 250284
V6_text.mov: audio mismatchs from previous build
stddev: 0.50 PSNR: 54.00 bytes: 11371244/ 11371244
blue_earth.mov: audio mismatchs from previous build
stddev: 0.40 PSNR: 55.92 bytes: 19681324/ 19681324
codeblue-interrupt01.mov: audio mismatchs from previous build
stddev: 0.02 PSNR: 79.21 bytes: 276524/ 276524
codeblue-interrupt06.mov: audio mismatchs from previous build
stddev: 0.31 PSNR: 58.03 bytes: 642924/ 642924
codeblue-plot08motor.mov: audio mismatchs from previous build
stddev: 0.29 PSNR: 58.81 bytes: 1534764/ 1534764
h263.mov: audio mismatchs from previous build
stddev: 0.45 PSNR: 54.95 bytes: 13511404/ 13511404
h263.trashed.mov: audio mismatchs from previous build
stddev: 0.45 PSNR: 54.95 bytes: 13511404/ 13511404
installfect_export.mov: audio mismatchs from previous build
stddev: 1.19 PSNR: 46.60 bytes: 10448044/ 10448044
oldepisode.mov: audio mismatchs from previous build
stddev: 1.09 PSNR: 47.35 bytes: 4588844/ 4588844
schlangenmannliten.mov: audio mismatchs from previous build
stddev: 0.28 PSNR: 59.01 bytes: 8820844/ 8820844
surge-1-16-B-Qclp.mov: audio mismatchs from previous build
stddev: 1.52 PSNR: 44.48 bytes: 1156524/ 1156524
vidoo_MP4_audio_Qcelp13k.k3g: audio mismatchs from previous build
stddev: 0.41 PSNR: 55.68 bytes: 743724/ 743724
8fe3b9dcd6d7e6db3375521c5c1b_Video_041606_002.3g2: audio mismatchs
from previous build
stddev: 0.02 PSNR: 78.98 bytes: 721004/ 721004
Test3gpp-mp4a.3g2: audio mismatchs from previous build
stddev: 0.01 PSNR: 90.74 bytes: 219244/ 219244
c8wwz2m0.3g2: audio mismatchs from previous build
stddev: 0.00 PSNR: 91.54 bytes: 241964/ 241964
qtaudio-qcelp-problem.3g2: audio mismatchs from previous build
stddev: 0.02 PSNR: 80.33 bytes: 208044/ 208044
test.3g2: audio same as previous build
tube.3g2: audio mismatchs from previous build
stddev: 0.00 PSNR: 98.65 bytes: 113004/ 113004
zg3dx2d6.3g2: audio mismatchs from previous build
stddev: 0.36 PSNR: 56.84 bytes: 486444/ 486444
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