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asrc_anullsrc: implement a request_frame callback for returning frames

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This is mainly useful for filters (like the sox synth), which
overwrite the content of the passed data.
This commit is contained in:
Stefano Sabatini 2011-09-17 03:17:06 +02:00
parent 44ab77db9e
commit e72aa524d8
3 changed files with 31 additions and 7 deletions
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10
doc/filters.texi
View File

@ -309,8 +309,10 @@ value is "-1".
@section anullsrc
Null audio source, never return audio frames. It is mainly useful as a
template and to be employed in analysis / debugging tools.
Null audio source, return unprocessed audio frames. It is mainly useful
as a template and to be employed in analysis / debugging tools, or as
the source for filters which ignore the input data (for example the sox
synth filter).
It accepts an optional sequence of @var{key}=@var{value} pairs,
separated by ":".
@ -331,6 +333,10 @@ is "stereo".
Check the channel_layout_map definition in
@file{libavcodec/audioconvert.c} for the mapping between strings and
channel layout values.
@item nb_samples, n
Set the number of samples per requested frames.
@end table
Follow some examples:

26
libavfilter/asrc_anullsrc.c
View File

@ -33,6 +33,8 @@ typedef struct {
int64_t channel_layout;
char *sample_rate_str;
int sample_rate;
int nb_samples; ///< number of samples per requested frame
int64_t pts;
} ANullContext;
#define OFFSET(x) offsetof(ANullContext, x)
@ -42,6 +44,8 @@ static const AVOption anullsrc_options[]= {
{ "cl", "set channel_layout", OFFSET(channel_layout_str), FF_OPT_TYPE_STRING, {.str = "stereo"}, 0, 0 },
{ "sample_rate", "set sample rate", OFFSET(sample_rate_str) , FF_OPT_TYPE_STRING, {.str = "44100"}, 0, 0 },
{ "r", "set sample rate", OFFSET(sample_rate_str) , FF_OPT_TYPE_STRING, {.str = "44100"}, 0, 0 },
{ "nb_samples", "set the number of samples per requested frame", OFFSET(nb_samples), FF_OPT_TYPE_INT, {.dbl = 1024}, 0, INT_MAX },
{ "n", "set the number of samples per requested frame", OFFSET(nb_samples), FF_OPT_TYPE_INT, {.dbl = 1024}, 0, INT_MAX },
{ NULL },
};
@ -92,15 +96,29 @@ static int config_props(AVFilterLink *outlink)
chans_nb = av_get_channel_layout_nb_channels(priv->channel_layout);
av_get_channel_layout_string(buf, sizeof(buf), chans_nb, priv->channel_layout);
av_log(outlink->src, AV_LOG_INFO,
"sample_rate:%d channel_layout:%"PRId64 " channel_layout_description:'%s'\n",
priv->sample_rate, priv->channel_layout, buf);
"sample_rate:%d channel_layout:%"PRId64 " channel_layout_description:'%s' nb_samples:%d\n",
priv->sample_rate, priv->channel_layout, buf, priv->nb_samples);
return 0;
}
static int request_frame(AVFilterLink *link)
static int request_frame(AVFilterLink *outlink)
{
return -1;
ANullContext *null = outlink->src->priv;
AVFilterBufferRef *samplesref;
samplesref =
avfilter_get_audio_buffer(outlink, AV_PERM_WRITE, null->nb_samples);
samplesref->pts = null->pts;
samplesref->pos = -1;
samplesref->audio->channel_layout = null->channel_layout;
samplesref->audio->sample_rate = outlink->sample_rate;
avfilter_filter_samples(outlink, avfilter_ref_buffer(samplesref, ~0));
avfilter_unref_buffer(samplesref);
null->pts += null->nb_samples;
return 0;
}
AVFilter avfilter_asrc_anullsrc = {

2
libavfilter/avfilter.h
View File

@ -30,7 +30,7 @@
#define LIBAVFILTER_VERSION_MAJOR 2
#define LIBAVFILTER_VERSION_MINOR 43
#define LIBAVFILTER_VERSION_MICRO 1
#define LIBAVFILTER_VERSION_MICRO 2
#define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
LIBAVFILTER_VERSION_MINOR, \