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af_volume: implement replaygain clipping prevention

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This adds a new "replaygain_noclip" option to the filter, and, if enabled,
limits the gain applied for tracks where clipping would occur.

Signed-off-by: Anton Khirnov <anton@khirnov.net>
This commit is contained in:
Alessandro Ghedini 2014-04-06 16:25:08 +02:00 committed by Anton Khirnov
parent ac976ed91e
commit aaab192df2
3 changed files with 23 additions and 6 deletions
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5
doc/filters.texi
View File

@ -676,6 +676,11 @@ Pre-amplification gain in dB to apply to the selected replaygain gain.
Default value for @var{replaygain_preamp} is 0.0.
@item replaygain_noclip
Prevent clipping by limiting the gain applied.
Default value for @var{replaygain_noclip} is 1.
@end table
@subsection Examples

23
libavfilter/af_volume.c
View File

@ -61,6 +61,8 @@ static const AVOption options[] = {
{ "album", "album gain is preferred", 0, AV_OPT_TYPE_CONST, { .i64 = REPLAYGAIN_ALBUM }, 0, 0, A, "replaygain" },
{ "replaygain_preamp", "Apply replaygain pre-amplification",
OFFSET(replaygain_preamp), AV_OPT_TYPE_DOUBLE, { .dbl = 0.0 }, -15.0, 15.0, A },
{ "replaygain_noclip", "Apply replaygain clipping prevention",
OFFSET(replaygain_noclip), AV_OPT_TYPE_INT, { .i64 = 1 }, 0, 1, A },
{ NULL },
};
@ -246,25 +248,34 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *buf)
if (sd && vol->replaygain != REPLAYGAIN_IGNORE) {
if (vol->replaygain != REPLAYGAIN_DROP) {
AVReplayGain *replaygain = (AVReplayGain*)sd->data;
int32_t gain;
float g;
int32_t gain = 100000;
uint32_t peak = 100000;
float g, p;
if (vol->replaygain == REPLAYGAIN_TRACK &&
replaygain->track_gain != INT32_MIN)
replaygain->track_gain != INT32_MIN) {
gain = replaygain->track_gain;
else if (replaygain->album_gain != INT32_MIN)
if (replaygain->track_peak != 0)
peak = replaygain->track_peak;
} else if (replaygain->album_gain != INT32_MIN) {
gain = replaygain->album_gain;
else {
if (replaygain->album_peak != 0)
peak = replaygain->album_peak;
} else {
av_log(inlink->dst, AV_LOG_WARNING, "Both ReplayGain gain "
"values are unknown.\n");
gain = 100000;
}
g = gain / 100000.0f;
p = peak / 100000.0f;
av_log(inlink->dst, AV_LOG_VERBOSE,
"Using gain %f dB from replaygain side data.\n", g);
vol->volume = pow(10, (g + vol->replaygain_preamp) / 20);
if (vol->replaygain_noclip)
vol->volume = FFMIN(vol->volume, 1.0 / p);
vol->volume_i = (int)(vol->volume * 256 + 0.5);
volume_init(vol);

1
libavfilter/af_volume.h
View File

@ -48,6 +48,7 @@ typedef struct VolumeContext {
enum PrecisionType precision;
enum ReplayGainType replaygain;
double replaygain_preamp;
int replaygain_noclip;
double volume;
int volume_i;
int channels;