So user can pick which channels to extract.
Signed-off-by: Paul B Mahol <one...@gmail.com>
---
doc/filters.texi | 15 ++++++++++++
libavfilter/af_channelsplit.c | 54 +++++++++++++++++++++++++++++++++++--------
2 files changed, 60 insertions(+), 9 deletions(-)
diff --git a/doc/filters.texi b/doc/filters.texi
index bd43a7ac6e..81310e1cdf 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -2208,8 +2208,14 @@ It accepts the following parameters:
@table @option
@item channel_layout
The channel layout of the input stream. The default is "stereo".
+@item channels
+The channel layout of the channels for extraction. The default is "all".
@end table
+@subsection Examples
+
+@itemize
+@item
For example, assuming a stereo input MP3 file,
@example
ffmpeg -i in.mp3 -filter_complex channelsplit out.mkv
@@ -2217,6 +2223,7 @@ ffmpeg -i in.mp3 -filter_complex channelsplit out.mkv
will create an output Matroska file with two audio streams, one containing only
the left channel and the other the right channel.
+@item
Split a 5.1 WAV file into per-channel files:
@example
ffmpeg -i in.wav -filter_complex
@@ -2226,6 +2233,14 @@ front_center.wav -map '[LFE]' lfe.wav -map '[SL]'
side_left.wav -map '[SR]'
side_right.wav
@end example
+@item
+Extract LFE from a 5.1 WAV file:
+@example
+ffmpeg -i in.wav -filter_complex 'channelsplit=channel_layout=5.1:LFE[LFE]'
+-map '[LFE]' lfe.wav
+@end example
+@end itemize
+
@section chorus
Add a chorus effect to the audio.
diff --git a/libavfilter/af_channelsplit.c b/libavfilter/af_channelsplit.c
index 8c6b00fe4f..d9b9a60420 100644
--- a/libavfilter/af_channelsplit.c
+++ b/libavfilter/af_channelsplit.c
@@ -38,6 +38,9 @@ typedef struct ChannelSplitContext {
uint64_t channel_layout;
char *channel_layout_str;
+ char *channels_str;
+
+ int map[64];
} ChannelSplitContext;
#define OFFSET(x) offsetof(ChannelSplitContext, x)
@@ -45,6 +48,7 @@ typedef struct ChannelSplitContext {
#define F AV_OPT_FLAG_FILTERING_PARAM
static const AVOption channelsplit_options[] = {
{ "channel_layout", "Input channel layout.", OFFSET(channel_layout_str),
AV_OPT_TYPE_STRING, { .str = "stereo" }, .flags = A|F },
+ { "channels", "Channels to extract.", OFFSET(channels_str),
AV_OPT_TYPE_STRING, { .str = "all" }, .flags = A|F },
{ NULL }
};
@@ -64,15 +68,46 @@ static av_cold int init(AVFilterContext *ctx)
}
nb_channels = av_get_channel_layout_nb_channels(s->channel_layout);
- for (i = 0; i < nb_channels; i++) {
- uint64_t channel =
av_channel_layout_extract_channel(s->channel_layout, i);
- AVFilterPad pad = { 0 };
- pad.type = AVMEDIA_TYPE_AUDIO;
- pad.name = av_get_channel_name(channel);
+ if (!strcmp(s->channels_str, "all")) {
+ for (i = 0; i < nb_channels; i++) {
+ uint64_t channel =
av_channel_layout_extract_channel(s->channel_layout, i);
+ AVFilterPad pad = { 0 };
+
+ pad.type = AVMEDIA_TYPE_AUDIO;
+ pad.name = av_get_channel_name(channel);
+
+ s->map[i] = i;
- if ((ret = ff_insert_outpad(ctx, i, &pad)) < 0) {
+ if ((ret = ff_insert_outpad(ctx, i, &pad)) < 0) {
+ return ret;
+ }
+ }
+ } else {
+ uint64_t channel_layout;
+ int nb_extracted_channels;
+
+ if ((ret = av_get_extended_channel_layout(s->channels_str,
&channel_layout, &nb_extracted_channels)) < 0)
return ret;
+
+ for (i = 0; i < nb_extracted_channels; i++) {
+ uint64_t channel =
av_channel_layout_extract_channel(channel_layout, i);
+ AVFilterPad pad = { 0 };
+
+ if ((ret = av_get_channel_layout_channel_index(s->channel_layout,
channel)) < 0) {
+ av_log(ctx, AV_LOG_ERROR, "Channel name '%s' not present in
channel layout '%s'.\n",
+ av_get_channel_name(channel), s->channel_layout_str);
+ return ret;
+ }
+
+ s->map[i] = ret;
+
+ pad.type = AVMEDIA_TYPE_AUDIO;
+ pad.name = av_get_channel_name(channel);
+
+ if ((ret = ff_insert_outpad(ctx, i, &pad)) < 0) {
+ return ret;
+ }
}
}
@@ -96,7 +131,7 @@ static int query_formats(AVFilterContext *ctx)
for (i = 0; i < ctx->nb_outputs; i++) {
AVFilterChannelLayouts *out_layouts = NULL;
- uint64_t channel =
av_channel_layout_extract_channel(s->channel_layout, i);
+ uint64_t channel =
av_channel_layout_extract_channel(s->channel_layout, s->map[i]);
if ((ret = ff_add_channel_layout(&out_layouts, channel)) < 0 ||
(ret = ff_channel_layouts_ref(out_layouts,
&ctx->outputs[i]->in_channel_layouts)) < 0)
@@ -109,6 +144,7 @@ static int query_formats(AVFilterContext *ctx)
static int filter_frame(AVFilterLink *inlink, AVFrame *buf)
{
AVFilterContext *ctx = inlink->dst;
+ ChannelSplitContext *s = ctx->priv;
int i, ret = 0;
for (i = 0; i < ctx->nb_outputs; i++) {
@@ -119,9 +155,9 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *buf)
break;
}
- buf_out->data[0] = buf_out->extended_data[0] =
buf_out->extended_data[i];
+ buf_out->data[0] = buf_out->extended_data[0] =
buf_out->extended_data[s->map[i]];
buf_out->channel_layout =
- av_channel_layout_extract_channel(buf->channel_layout, i);
+ av_channel_layout_extract_channel(buf->channel_layout, s->map[i]);
buf_out->channels = 1;
ret = ff_filter_frame(ctx->outputs[i], buf_out);
--
2.11.0
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