@@ -1060,6 +1060,11 @@ Either a channel layout name from channel_layout_map in

 @file{libavutil/channel_layout.c} or its corresponding integer representation

 from the AV_CH_LAYOUT_* macros in @file{libavutil/channel_layout.h}

+@item channels

+The number of channels of the incoming audio buffers.

+If both @var{channels} and @var{channel_layout} are specified, then they

+must be consistent.

+

 @end table

 For example:

@@ -55,6 +55,7 @@ typedef struct {

     int sample_rate;

     enum AVSampleFormat sample_fmt;

     char               *sample_fmt_str;

+    int channels;

     uint64_t channel_layout;

     char    *channel_layout_str;

@@ -240,6 +241,7 @@ static const AVOption abuffer_options[] = {

     { "time_base",      NULL, OFFSET(time_base),           AV_OPT_TYPE_RATIONAL, { .dbl = 0 }, 0, INT_MAX, FLAGS },

     { "sample_rate",    NULL, OFFSET(sample_rate),         AV_OPT_TYPE_INT,      { .i64 = 0 }, 0, INT_MAX, FLAGS },

     { "sample_fmt",     NULL, OFFSET(sample_fmt_str),      AV_OPT_TYPE_STRING, .flags = FLAGS },

+    { "channels",       NULL, OFFSET(channels),            AV_OPT_TYPE_INT,      { .i64 = 0 }, 0, INT_MAX, FLAGS },

     { "channel_layout", NULL, OFFSET(channel_layout_str),  AV_OPT_TYPE_STRING, .flags = FLAGS },

     { NULL },

 };

@@ -265,6 +267,9 @@ static av_cold int init_audio(AVFilterContext *ctx, const char *args)

         goto fail;

     }

+    if (s->channel_layout_str) {

+        int n;

+        /* TODO reindent */

     s->channel_layout = av_get_channel_layout(s->channel_layout_str);

     if (!s->channel_layout) {

         av_log(ctx, AV_LOG_ERROR, "Invalid channel layout '%s'\n",

@@ -272,6 +277,24 @@ static av_cold int init_audio(AVFilterContext *ctx, const char *args)

         ret = AVERROR(EINVAL);

         goto fail;

     }

+        n = av_get_channel_layout_nb_channels(s->channel_layout);

+        if (s->channels) {

+            if (n != s->channels) {

+                av_log(ctx, AV_LOG_ERROR,

+                       "Mismatching channel count %d and layout '%s' "

+                       "(%d channels)\n",

+                       s->channels, s->channel_layout_str, n);

+                ret = AVERROR(EINVAL);

+                goto fail;

+            }

+        }

+        s->channels = n;

+    } else if (!s->channels) {

+        av_log(ctx, AV_LOG_ERROR, "Neither number of channels nor "

+                                  "channel layout specified\n");

+        ret = AVERROR(EINVAL);

+        goto fail;

+    }

     if (!(s->fifo = av_fifo_alloc(sizeof(AVFilterBufferRef*)))) {

         ret = AVERROR(ENOMEM);

@@ -324,7 +347,9 @@ static int query_formats(AVFilterContext *ctx)

         ff_add_format(&samplerates,       c->sample_rate);

         ff_set_common_samplerates(ctx, samplerates);

-        ff_add_channel_layout(&channel_layouts, c->channel_layout);

+        ff_add_channel_layout(&channel_layouts,

+                              c->channel_layout ? c->channel_layout :

+                              FF_COUNT2LAYOUT(c->channels));

         ff_set_common_channel_layouts(ctx, channel_layouts);

         break;

     default: