[FFmpeg-devel] [PATCH] lavf: add more beep options to sine asrc

[Nicolas George]

Thanks for the patch.

Le quintidi 15 vendémiaire, an CCXXVI, Michael Bradshaw a écrit :
> From: Michael Bradshaw <mjbshaw at google.com>
> 
> Signed-off-by: Michael Bradshaw <mjbshaw at google.com>
> ---
>  doc/filters.texi        | 13 ++++++++++++-
>  libavfilter/asrc_sine.c | 17 +++++++++++++----
>  2 files changed, 25 insertions(+), 5 deletions(-)
> 
> diff --git a/doc/filters.texi b/doc/filters.texi
> index 57189c77b0..ec1c335950 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -4624,7 +4624,18 @@ Set the carrier frequency. Default is 440 Hz.
>  
>  @item beep_factor, b
>  Enable a periodic beep every second with frequency @var{beep_factor} times
> -the carrier frequency. Default is 0, meaning the beep is disabled.
> +the carrier frequency. Default is 0, meaning the beep is disabled. If
> + at var{frequency} is 0, this value is interpreted as the beep frequency (in Hertz)
> +(rather than a multiplier of the @var{frequency}).
> +
> + at item beep_delay
> +The delay for the first beep, in seconds. Default is 0.
> +
> + at item beep_period
> +The time beriod between two beeps, in seconds. Default is 1.
> +
> + at item beep_duration
> +The duration of a beep, in seconds. Default is 0.04.
>  
>  @item sample_rate, r
>  Specify the sample rate, default is 44100.
> diff --git a/libavfilter/asrc_sine.c b/libavfilter/asrc_sine.c
> index 3a87210b4b..643952792f 100644
> --- a/libavfilter/asrc_sine.c
> +++ b/libavfilter/asrc_sine.c
> @@ -32,6 +32,9 @@ typedef struct SineContext {
>      const AVClass *class;
>      double frequency;
>      double beep_factor;
> +    double beep_delay;
> +    double beep_period_opt;
> +    double beep_duration;
>      char *samples_per_frame;
>      AVExpr *samples_per_frame_expr;
>      int sample_rate;
> @@ -71,6 +74,9 @@ static const AVOption sine_options[] = {
>      OPT_DBL("f",                 frequency,            440, 0, DBL_MAX,   "set the sine frequency",),
>      OPT_DBL("beep_factor",       beep_factor,            0, 0, DBL_MAX,   "set the beep frequency factor",),
>      OPT_DBL("b",                 beep_factor,            0, 0, DBL_MAX,   "set the beep frequency factor",),

> +    OPT_DBL("beep_delay",        beep_delay,             0, 0, DBL_MAX,   "set the delay for the first beep",),
> +    OPT_DBL("beep_period",       beep_period_opt,        1, DBL_MIN, DBL_MAX, "set the gap between beeps",),
> +    OPT_DBL("beep_duration",     beep_duration,       0.04, DBL_MIN, DBL_MAX, "set the duration of a beep",),

I think these should use OPT_DUR / AV_OPT_TYPE_DURATION rather than
doubles. Also, DBL_MIN seems strange: I do not think a negative value
makes sense.

>      OPT_INT("sample_rate",       sample_rate,        44100, 1, INT_MAX,   "set the sample rate",),
>      OPT_INT("r",                 sample_rate,        44100, 1, INT_MAX,   "set the sample rate",),
>      OPT_DUR("duration",          duration,               0, 0, INT64_MAX, "set the audio duration",),
> @@ -152,10 +158,13 @@ static av_cold int init(AVFilterContext *ctx)
>      make_sin_table(sine->sin);
>  
>      if (sine->beep_factor) {
> -        sine->beep_period = sine->sample_rate;
> -        sine->beep_length = sine->beep_period / 25;
> -        sine->dphi_beep = ldexp(sine->beep_factor * sine->frequency, 32) /
> -                          sine->sample_rate + 0.5;
> +        unsigned beep_start = sine->beep_delay * sine->sample_rate;
> +        double beep_frequency = (sine->frequency ? sine->frequency : 1.0) *
> +                                sine->beep_factor;

> +        sine->beep_period = sine->beep_period_opt * sine->sample_rate;

With integer durations, av_rescale() would be better.

> +        sine->beep_index = (sine->beep_period - beep_start) % sine->beep_period;

I think this will produce strange results if beep_start is greater than
beep_period. Maybe document the limitation, or adjust the arithmetic.

> +        sine->beep_length = sine->beep_duration * sine->sample_rate;
> +        sine->dphi_beep = ldexp(beep_frequency, 32) / sine->sample_rate + 0.5;
>      }
>  
>      ret = av_expr_parse(&sine->samples_per_frame_expr,

Regards,

-- 
  Nicolas George
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