[FFmpeg-devel] [PATCH] QCELP decoder

[Michael Niedermayer]

On Wed, Nov 12, 2008 at 02:22:40PM -0800, Kenan Gillet wrote:
> 
> On Nov 12, 2008, at 11:57 AM, Michael Niedermayer wrote:
> 
> > On Wed, Nov 12, 2008 at 09:05:02AM -0800, Kenan Gillet wrote:
> >>
> >> On Nov 11, 2008, at 10:00 AM, Michael Niedermayer wrote:
> >>
> >>> On Sun, Nov 09, 2008 at 09:49:20PM -0800, Kenan Gillet wrote:
> > [...]
> >>>> +        const float *predictors = (q->prev_framerate !=
> >>>> RATE_OCTAVE ||
> >>>> +                                   q->prev_framerate != I_F_Q ? q-
> >>>>> prev_lspf
> >>>> +                                                              : q-
> >>>>> predictor_lspf);
> >>>
> >>> hmmmmmmm
> >>> hmm
> >>>
> >>> Which value is not unequal to either RATE_OCTAVE or I_F_Q ?
> >>
> >> q->prev_framerate : framerate of the previous frame
> >> q->framerate: framerate of the current frame
> >> :)
> >
> > there is no q->framerate in there :)
> >
> >
> >>
> >>
> >> The predictor changes based on the rate of the previous frame.
> >>
> >>
> >>>
> >>>
> >>> Are you testing the code in each patch iteration?
> >>
> >> I do check the output to wav of all the test files I have for every
> >> commit in my svn.
> >
> > great, now i feel better, this is a good strategy
> >
> > [...]
> >>>> +        break;
> >>>> +    case RATE_OCTAVE:
> >>>> +        cbseed = q->first16bits;
> >>>> +        for (i = 0; i < 8; i++) {
> >>>> +            tmp_gain = gain[i] * (QCELP_SQRT1887 / 32768.0);
> >>>> +            for (j = 0; j < 20; j++) {
> >>>> +                cbseed = 521 * cbseed + 259;
> >>>> +                *cdn_vector++ = tmp_gain * (int16_t)cbseed;
> >>>> +            }
> >>>> +        }
> >>>> +        break;
> >>>> +    case I_F_Q:
> >>>> +        cbseed = -44; // random codebook index
> >>>> +        for (i = 0; i < 4; i++) {
> >>>> +            tmp_gain = gain[i] * QCELP_RATE_FULL_CODEBOOK_RATIO;
> >>>> +            for (j = 0; j < 40; j++)
> >>>> +                *cdn_vector++ = tmp_gain *
> >>>> qcelp_rate_full_codebook[cbseed++ & 127];
> >>>> +        }
> >>>> +        break;
> >>>> +    }
> >>>> +}
> >>>> +
> >>>
> >>>> +/**
> >>>> + * Apply generic gain control.
> >>>> + *
> >>>> + * @param v_out output vector
> >>>> + * @param v_in gain-controlled vector
> >>>> + * @param v_ref vector to control gain of
> >>>> + *
> >>>> + * TIA/EIA/IS-733 2.4.8.3-2/3/4/5, 2.4.8.6
> >>>> + */
> >>>> +static void apply_gain_ctrl(float *v_out,
> >>>> +                            const float *v_ref,
> >>>> +                            const float *v_in) {
> >>>> +    int   i, j, len;
> >>>> +    float scalefactor;
> >>>> +
> >>>> +    for (i = 0, j = 0; i < 4; i++) {
> >>>> +        scalefactor = ff_dot_productf(v_in + j, v_in + j, 40);
> >>>
> >>>> +        if (scalefactor) {
> >>>> +            scalefactor = sqrt(ff_dot_productf(v_ref + j, v_ref +
> >>>> j, 40) / scalefactor);
> >>>> +            for (len = j + 40; j < len; j++)
> >>>> +                v_out[j] = scalefactor * v_in[j];
> >>>> +        } else {
> >>>> +            memset(v_out + j, 0,  40 * sizeof(float));
> >>>> +            j += 40;
> >>>> +        }
> >>>
> >>> assuming this is correct
> >>
> >> it is undefined in the specs and the reference code is setting
> >> scalefactor
> >>  only if both dot product are not zero but sill assign
> >> v_out[j] = v_in[j] * scalefactor
> >>  with the unassigned scalefactor :(
> >
> > interresting, i guess then a  if() av_log_missing_feature() would be
> > a good idea, so we will get a sample that triggers this
> 
>  From my investigation, an initial SILENCE frame could trigger it,
> and on this particular case, v_in & v_out would be 0 vectors. I don't
> think another case could trigger it but i have not investigate enough
> to be sure, maybe a very long succession of SILENCE might trigger it
> too.

as long as v_in is 0, making v_out 0 should be fine i guess ...


> 
> I am not sure that carrying the AVCodecContext into this function to add
> an av_log_missing_feature would be worth it.

NULL should do as context

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Old school: Use the lowest level language in which you can solve the problem
            conveniently.
New school: Use the highest level language in which the latest supercomputer
            can solve the problem without the user falling asleep waiting.
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