[FFmpeg-devel] [PATCH] avfilter/af_tremolo: make it bit-exact with sox effect of same name

[Kyle Swanson]

>  s->table = av_malloc_array(inlink->sample_rate, sizeof(*s->table));


Just wondering. Is there a reason that the size of s->table is
(inlink->sample_rate)  and not (1.0 / inlink->sample_rate) ?

Thanks!
Kyle

On Wed, Sep 23, 2015 at 6:16 PM, Kyle Swanson <k at ylo.ph> wrote:
> Looks good. Thanks for the clean-up.
>
> On Wed, Sep 23, 2015 at 4:22 PM, Paul B Mahol <onemda at gmail.com> wrote:
>> Signed-off-by: Paul B Mahol <onemda at gmail.com>
>> ---
>>  libavfilter/Makefile     |  2 +-
>>  libavfilter/af_tremolo.c | 45 ++++++++++++++++++++++-----------------------
>>  2 files changed, 23 insertions(+), 24 deletions(-)
>>
>> diff --git a/libavfilter/Makefile b/libavfilter/Makefile
>> index 7054275..c70887e 100644
>> --- a/libavfilter/Makefile
>> +++ b/libavfilter/Makefile
>> @@ -85,7 +85,7 @@ OBJS-$(CONFIG_SILENCEREMOVE_FILTER)          += af_silenceremove.o
>>  OBJS-$(CONFIG_STEREOTOOLS_FILTER)            += af_stereotools.o
>>  OBJS-$(CONFIG_STEREOWIDEN_FILTER)            += af_stereowiden.o
>>  OBJS-$(CONFIG_TREBLE_FILTER)                 += af_biquads.o
>> -OBJS-$(CONFIG_TREMOLO_FILTER)                += af_tremolo.o generate_wave_table.o
>> +OBJS-$(CONFIG_TREMOLO_FILTER)                += af_tremolo.o
>>  OBJS-$(CONFIG_VOLUME_FILTER)                 += af_volume.o
>>  OBJS-$(CONFIG_VOLUMEDETECT_FILTER)           += af_volumedetect.o
>>
>> diff --git a/libavfilter/af_tremolo.c b/libavfilter/af_tremolo.c
>> index 6335401..0ae7a7c 100644
>> --- a/libavfilter/af_tremolo.c
>> +++ b/libavfilter/af_tremolo.c
>> @@ -22,15 +22,13 @@
>>  #include "avfilter.h"
>>  #include "internal.h"
>>  #include "audio.h"
>> -#include "generate_wave_table.h"
>>
>>  typedef struct TremoloContext {
>>      const AVClass *class;
>>      double freq;
>>      double depth;
>> -    double *wave_table;
>> -    int wave_table_index;
>> -    int sample_rate;
>> +    double *table;
>> +    int index;
>>  } TremoloContext;
>>
>>  #define OFFSET(x) offsetof(TremoloContext, x)
>> @@ -44,20 +42,11 @@ static const AVOption tremolo_options[] = {
>>
>>  AVFILTER_DEFINE_CLASS(tremolo);
>>
>> -static double trem_env(AVFilterContext *ctx)
>> -{
>> -    TremoloContext *s = ctx->priv;
>> -    double env = s->wave_table[s->wave_table_index];
>> -    s->wave_table_index++;
>> -    if (s->wave_table_index >= s->sample_rate / s->freq)
>> -        s->wave_table_index = 0;
>> -    return 1.0 - (s->depth * env);
>> -}
>> -
>>  static int filter_frame(AVFilterLink *inlink, AVFrame *in)
>>  {
>>      AVFilterContext *ctx = inlink->dst;
>>      AVFilterLink *outlink = ctx->outputs[0];
>> +    TremoloContext *s = ctx->priv;
>>      const double *src = (const double *)in->data[0];
>>      const int channels = inlink->channels;
>>      const int nb_samples = in->nb_samples;
>> @@ -78,12 +67,13 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
>>      dst = (double *)out->data[0];
>>
>>      for (n = 0; n < nb_samples; n++) {
>> -        const double env = trem_env(ctx);
>> -
>>          for (c = 0; c < channels; c++)
>> -            dst[c] = src[c] * env;
>> +            dst[c] = src[c] * s->table[s->index];
>>          dst += channels;
>>          src += channels;
>> +        s->index++;
>> +        if (s->index >= inlink->sample_rate)
>> +            s->index = 0;
>>      }
>>
>>      if (in != out)
>> @@ -125,21 +115,30 @@ static int query_formats(AVFilterContext *ctx)
>>  static av_cold void uninit(AVFilterContext *ctx)
>>  {
>>      TremoloContext *s = ctx->priv;
>> -    av_freep(&s->wave_table);
>> +    av_freep(&s->table);
>>  }
>>
>>  static int config_input(AVFilterLink *inlink)
>>  {
>>      AVFilterContext *ctx = inlink->dst;
>>      TremoloContext *s = ctx->priv;
>> +    const double offset = 1. - s->depth / 2.;
>> +    int i;
>>
>> -    s->sample_rate = inlink->sample_rate;
>> -    s->wave_table = av_malloc_array(s->sample_rate / s->freq, sizeof(*s->wave_table));
>> -    if (!s->wave_table)
>> +    s->table = av_malloc_array(inlink->sample_rate, sizeof(*s->table));
>> +    if (!s->table)
>>          return AVERROR(ENOMEM);
>>
>> -    ff_generate_wave_table(WAVE_SIN, AV_SAMPLE_FMT_DBL, s->wave_table, s->sample_rate / s->freq, 0.0, 1.0, 0.0);
>> -    s->wave_table_index = 0;
>> +    for (i = 0; i < inlink->sample_rate; i++) {
>> +        double env = s->freq * i / inlink->sample_rate;
>> +
>> +        env = sin(2 * M_PI * fmod(env + 0.25, 1.0));
>> +
>> +        s->table[i] = env * (1 - fabs(offset)) + offset;
>> +    }
>> +
>> +    s->index = 0;
>> +
>>      return 0;
>>  }
>>
>> --
>> 1.9.1
>>
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