[FFmpeg-devel] [PATCH] avcodec/dcaenc: Initial implementation of ADPCM encoding for DCA encoder

Даниил Чередник dan.cherednik at gmail.com
Mon May 8 13:49:56 EEST 2017


Yes, now it is not easy to hear the difference.  I found one track on
Marantz demo cd where quantization noise is noticeable without ADPCM.
About bit allocation. Current algorithm fails (av_assert0(used_abits !=
USED_1ABITS)) even with 250-320kbps on some tracks - probably I can fix it.

Thank you.

On Mon, May 8, 2017 at 7:59 AM, Rostislav Pehlivanov <atomnuker at gmail.com>
wrote:

> On 6 May 2017 at 11:47, Даниил Чередник <dan.cherednik at gmail.com> wrote:
>
> > Tiny fix: missed inline attr.
> >
> > On Thu, May 4, 2017 at 1:17 AM, Даниил Чередник <dan.cherednik at gmail.com
> >
> > wrote:
> >
> > > All notices were fixed. Also I found issue with uninitialized subband
> > > buffer - fixed. New patch attached.
> > >
> > > On Wed, May 3, 2017 at 7:49 AM, Rostislav Pehlivanov <
> > atomnuker at gmail.com>
> > > wrote:
> > >
> > >> On 2 May 2017 at 22:53, Даниил Чередник <dan.cherednik at gmail.com>
> > wrote:
> > >>
> > >> > Hi.
> > >> >
> > >> > This patch introduces initial implementation of subband ADPCM
> encoding
> > >> for
> > >> > DCA codec.
> > >> >
> > >> > Some results:
> > >> >
> > >> > sample:
> > >> >
> > >> > https://yadi.sk/d/B_3sVskM3HZiWK - original
> > >> >
> > >> > https://yadi.sk/d/7CK47Nt63HZiWf - without adpcm
> > >> >
> > >> > https://yadi.sk/d/25q1JDV93HZiWq - with adpcm
> > >> >
> > >> > chirp tone:
> > >> >
> > >> > https://yadi.sk/i/tZKHoJ1d3HZk4c
> > >> >
> > >> > Right now this feature is disabled by default. But it is ready to
> try
> > >> > using -dca_adpcm 1 option.
> > >> >
> > >> > There are some issues, should be solved before enabling this feature
> > by
> > >> > default:
> > >> >
> > >> > 1. Speed up: I am trying to find best filter in each subband. But
> with
> > >> real
> > >> > signal, usually only few subbands has significant prediction gain.
> The
> > >> idea
> > >> > is try to analyze FFT spectrum (which is already calculated), to
> check
> > >> is
> > >> > particular subband looks like tonal or noise. If subband is noise
> like
> > >> - do
> > >> > not try to find best LPC predictor.
> > >> >
> > >> > 2. Modify psychoacoustic to use prediction gain for bit allocation.
> > >> Right
> > >> > now ADPCM encoded block can get some extra bits.
> > >> >
> > >> > 3. Tuning the prediction gain threshold.
> > >> >
> > >> >
> > >> > Thank you.
> > >> > --
> > >> > Daniil Cherednik
> > >> >
> > >> > _______________________________________________
> > >> > ffmpeg-devel mailing list
> > >> > ffmpeg-devel at ffmpeg.org
> > >> > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> > >> >
> > >> >
> > >> >+static int64_t calc_corr(const int32_t *x, int len, int j, int k)
> > >>
> > >> Add inline attrib? Seems appropriate here.
> > >>
> > >>
> > >> >+for (n = 0; n < len; n++) {
> > >> >+        s += MUL64(x[n-j], x[n-k]);
> > >> >+    }
> > >>
> > >> For loops with 1 line we leave the brackets out.
> > >>
> > >>
> > >> >+for (i = 0; i <= DCA_ADPCM_COEFFS; i++) {
> > >> >+        for (j = i; j <= DCA_ADPCM_COEFFS; j++) {
> > >> >+            corr[k++] = calc_corr(in+4, len, i, j);
> > >> >+        }
> > >> >+    }
> > >>
> > >> Same
> > >>
> > >>
> > >> >+    for (i = 0; i < len + DCA_ADPCM_COEFFS; i++) {
> > >> >+        max |= FFABS(in[i]);
> > >> >+    }
> > >>
> > >> Same
> > >>
> > >>
> > >> >for (ch = 0; ch < c->fullband_channels; ch++) {
> > >> >+        for (band = 0; band < 32; band++) {
> > >> >+            if (c->prediction_mode[ch][band] >= 0) {
> > >> >+                quantize_adpcm_subband(c, ch, band);
> > >> >+            }
> > >> >+        }
> > >> >+    }
> > >>
> > >> Same
> > >>
> > >>
> > >> >+    for (ch = 0; ch < c->fullband_channels; ch++) {
> > >> >+        for (band = 0; band < 32; band++) {
> > >> >+            if (c->prediction_mode[ch][band] == -1) {
> > >> >+                for (sample = 0; sample < SUBBAND_SAMPLES;
> sample++) {
> > >> >+                    c->quantized[ch][band][sample] =
> > >> quantize_value(c->subband[ch][band][sample], c->quant[ch][band]);
> > >> >+                }
> > >> >+            }
> > >> >+        }
> > >> >+    }
> > >>
> > >> Same, 4 whole whitespace lines added here.
> > >>
> > >>
> > >> >+    if (c->bitrate_index == 3) {
> > >> >+        step_size = ff_dca_lossless_quant[c->abits[ch][band]];
> > >> >+    } else {
> > >> >+        step_size = ff_dca_lossy_quant[c->abits[ch][band]];
> > >> >+    }
> > >>
> > >> Same
> > >>
> > >>
> > >> >for (;;) {
> > >>
> > >> while (1) {
> > >>
> > >> >+        if (i++ == last_pos)
> > >> >+            break;
> > >>
> > >> Better yet remove the infinite loop and just use a normal for () loop.
> > >>
> > >>
> > >> >+static inline void ff_dca_core_dequantize(int32_t *output, const
> > int32_t
> > >> *input,
> > >> >+                              int32_t step_size, int32_t scale, int
> > >> residual, int len)
> > >>
> > >> Fix second line's alignment.
> > >>
> > >>
> > >> >+struct premultiplied_coeffs {
> > >> >+    int32_t aa[10];
> > >> >+};
> > >>
> > >> I think it would be simpler to just use int32_t
> premultiplied_coeffs[10]
> > >> instead of a struct.
> > >>
> > >>
> > >> Apart from these style issues patch looks fine. I'll be able to test
> it
> > in
> > >> a day.
> > >> _______________________________________________
> > >> ffmpeg-devel mailing list
> > >> ffmpeg-devel at ffmpeg.org
> > >> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> > >>
> > >
> > >
> > >
> > > --
> > > Daniil Cherednik
> > >
> >
> >
> >
> > --
> > Daniil Cherednik
> >
> > _______________________________________________
> > ffmpeg-devel mailing list
> > ffmpeg-devel at ffmpeg.org
> > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> >
> >
> Tested, there's a difference though looking at the spectrum is the only way
> to see it. The encoder only supports bitrates higher than ~251kbps which
> isn't enough to really make a big difference. Tried to reduce it but the
> bit allocation algorithm of the encoder broke.
>
> Anyway, thanks, pushed the patch.
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>



-- 
Daniil Cherednik


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