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avfilter/af_amerge: add layout_mode option to control output channel layout

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Signed-off-by: Marton Balint <cus@passwd.hu>
This commit is contained in:
Marton Balint
2025-11-28 23:59:18 +01:00
parent 4e0a8b745a
commit 3d667b147a
2 changed files with 85 additions and 17 deletions
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49
doc/filters.texi
View File

@@ -2436,6 +2436,11 @@ Only used if option named @var{start} is set to @code{-1}.
Merge two or more audio streams into a single multi-channel stream.
All inputs must have the same sample rate, and format.
If inputs do not have the same duration, the output will stop with the
shortest.
The filter accepts the following options:
@table @option
@@ -2443,15 +2448,25 @@ The filter accepts the following options:
@item inputs
Set the number of inputs. Default is 2.
@end table
@item layout_mode
If the channel layouts of the inputs are disjoint, and therefore compatible,
the channel layout of the output will be set accordingly and the channels
will be reordered as necessary. If the channel layouts of the inputs are not
disjoint, the output will have all the channels of the first input then all
the channels of the second input, in that order, and the channel layout of
the output will be the default value corresponding to the total number of
channels.
This option controls how the output channel layout is determined and if the
audio channels are reordered during merge.
@table @option
@item legacy
This is the mode how the filter behaved historically so it is the default.
If the channel layouts of the inputs are known and disjoint, and therefore
compatible, the channel layout of the output will be set accordingly and the
channels will be reordered as necessary. If the channel layouts of the inputs
are not disjoint, some of them are unknown, or they are using special channel
layouts, such as ambisonics, the output will have all the channels of the first
input then all the channels of the second input, in that order, and the channel
layout of the output will be the default value corresponding to the total
number of channels.
For example, if the first input is in 2.1 (FL+FR+LF) and the second input
is FC+BL+BR, then the output will be in 5.1, with the channels in the
@@ -2462,10 +2477,22 @@ On the other hand, if both input are in stereo, the output channels will be
in the default order: a1, a2, b1, b2, and the channel layout will be
arbitrarily set to 4.0, which may or may not be the expected value.
All inputs must have the same sample rate, and format.
@item reset
This mode ignores the input channel layouts and does no channel reordering.
The output will have all the channels of the first input, then all the channels
of the second input, in that order, and so on.
If inputs do not have the same duration, the output will stop with the
shortest.
The output channel layout will only specify the total channel count.
@item normal
This mode keeps channel name and designation information from the input
channels and does no channel reordering. The output will have all the channels
of the first input, then all the channels of the second input, in that order,
and so on.
@end table
@end table
@subsection Examples

53
libavfilter/af_amerge.c
View File

@@ -23,6 +23,7 @@
* Audio merging filter
*/
#include "libavutil/avassert.h"
#include "libavutil/avstring.h"
#include "libavutil/bprint.h"
#include "libavutil/channel_layout.h"
@@ -43,14 +44,27 @@ typedef struct AMergeContext {
struct amerge_input {
int nb_ch; /**< number of channels for the input */
} *in;
int layout_mode; /**< the method for determining the output channel layout */
} AMergeContext;
#define OFFSET(x) offsetof(AMergeContext, x)
#define FLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
enum LayoutModes {
LM_LEGACY,
LM_RESET,
LM_NORMAL,
NB_LAYOUTMODES
};
static const AVOption amerge_options[] = {
{ "inputs", "specify the number of inputs", OFFSET(nb_inputs),
AV_OPT_TYPE_INT, { .i64 = 2 }, 1, SWR_CH_MAX, FLAGS },
{ "layout_mode", "method used to determine the output channel layout", OFFSET(layout_mode),
AV_OPT_TYPE_INT, { .i64 = LM_LEGACY }, 0, NB_LAYOUTMODES - 1, FLAGS, .unit = "layout_mode"},
{ "legacy", NULL, 0, AV_OPT_TYPE_CONST, {.i64 = LM_LEGACY }, 0, 0, FLAGS, .unit = "layout_mode" },
{ "reset", NULL, 0, AV_OPT_TYPE_CONST, {.i64 = LM_RESET }, 0, 0, FLAGS, .unit = "layout_mode" },
{ "normal", NULL, 0, AV_OPT_TYPE_CONST, {.i64 = LM_NORMAL }, 0, 0, FLAGS, .unit = "layout_mode" },
{ NULL }
};
@@ -101,9 +115,16 @@ static int query_formats(AVFilterContext *ctx)
av_log(ctx, AV_LOG_ERROR, "Too many channels (max %d)\n", SWR_CH_MAX);
return AVERROR(EINVAL);
}
ret = av_channel_layout_custom_init(&outlayout, nb_ch);
if (ret < 0)
return ret;
for (int i = 0, ch_idx = 0; i < s->nb_inputs; i++) {
for (int j = 0; j < s->in[i].nb_ch; j++) {
enum AVChannel id = av_channel_layout_channel_from_index(INLAYOUT(ctx, i), j);
if (INLAYOUT(ctx, i)->order == AV_CHANNEL_ORDER_CUSTOM)
outlayout.u.map[ch_idx] = INLAYOUT(ctx, i)->u.map[j];
else
outlayout.u.map[ch_idx].id = (id == AV_CHAN_NONE ? AV_CHAN_UNKNOWN : id);
if (id >= 0 && id < 64) {
outmask |= (1ULL << id);
native_layout_routes[id] = ch_idx;
@@ -112,6 +133,9 @@ static int query_formats(AVFilterContext *ctx)
ch_idx++;
}
}
switch (s->layout_mode) {
case LM_LEGACY:
av_channel_layout_uninit(&outlayout);
if (av_popcount64(outmask) != nb_ch) {
av_log(ctx, AV_LOG_WARNING,
"Input channel layouts overlap: "
@@ -125,22 +149,39 @@ static int query_formats(AVFilterContext *ctx)
s->route[native_layout_routes[c]] = ch_idx++;
av_channel_layout_from_mask(&outlayout, outmask);
}
break;
case LM_RESET:
av_channel_layout_uninit(&outlayout);
outlayout.order = AV_CHANNEL_ORDER_UNSPEC;
outlayout.nb_channels = nb_ch;
break;
case LM_NORMAL:
ret = av_channel_layout_retype(&outlayout, 0, AV_CHANNEL_LAYOUT_RETYPE_FLAG_CANONICAL);
if (ret < 0)
goto out;
break;
default:
av_unreachable("Invalid layout_mode");
}
if ((ret = ff_set_common_formats_from_list(ctx, packed_sample_fmts)) < 0)
return ret;
goto out;
for (i = 0; i < s->nb_inputs; i++) {
layouts = NULL;
if ((ret = ff_add_channel_layout(&layouts, INLAYOUT(ctx, i))) < 0)
return ret;
goto out;
if ((ret = ff_channel_layouts_ref(layouts, &ctx->inputs[i]->outcfg.channel_layouts)) < 0)
return ret;
goto out;
}
layouts = NULL;
if ((ret = ff_add_channel_layout(&layouts, &outlayout)) < 0)
return ret;
goto out;
if ((ret = ff_channel_layouts_ref(layouts, &ctx->outputs[0]->incfg.channel_layouts)) < 0)
return ret;
goto out;
return ff_set_common_all_samplerates(ctx);
ret = ff_set_common_all_samplerates(ctx);
out:
av_channel_layout_uninit(&outlayout);
return ret;
}
static int config_output(AVFilterLink *outlink)