diff --git a/libavdevice/alsa-audio-enc.c b/libavdevice/alsa-audio-enc.c
index 0f4e4a2c7a..83e1d2f85f 100644
--- a/libavdevice/alsa-audio-enc.c
+++ b/libavdevice/alsa-audio-enc.c
@@ -47,12 +47,17 @@
 static av_cold int audio_write_header(AVFormatContext *s1)
 {
     AlsaData *s = s1->priv_data;
-    AVStream *st;
+    AVStream *st = NULL;
     unsigned int sample_rate;
     enum AVCodecID codec_id;
     int res;
 
+    if (s1->nb_streams != 1 || s1->streams[0]->codec->codec_type != AVMEDIA_TYPE_AUDIO) {
+        av_log(s1, AV_LOG_ERROR, "Only a single audio stream is supported.\n");
+        return AVERROR(EINVAL);
+    }
     st = s1->streams[0];
+
     sample_rate = st->codec->sample_rate;
     codec_id    = st->codec->codec_id;
     res = ff_alsa_open(s1, SND_PCM_STREAM_PLAYBACK, &sample_rate,
@@ -80,6 +85,10 @@ static int audio_write_packet(AVFormatContext *s1, AVPacket *pkt)
     uint8_t *buf = pkt->data;
 
     size /= s->frame_size;
+    if (pkt->dts != AV_NOPTS_VALUE)
+        s->timestamp = pkt->dts;
+    s->timestamp += pkt->duration ? pkt->duration : size;
+
     if (s->reorder_func) {
         if (size > s->reorder_buf_size)
             if (ff_alsa_extend_reorder_buf(s, size))
@@ -112,7 +121,7 @@ audio_get_output_timestamp(AVFormatContext *s1, int stream,
     snd_pcm_sframes_t delay = 0;
     *wall = av_gettime();
     snd_pcm_delay(s->h, &delay);
-    *dts = s1->streams[0]->cur_dts - delay;
+    *dts = s->timestamp - delay;
 }
 
 AVOutputFormat ff_alsa_muxer = {
diff --git a/libavdevice/alsa-audio.h b/libavdevice/alsa-audio.h
index 44b7c72fc0..583c9119ac 100644
--- a/libavdevice/alsa-audio.h
+++ b/libavdevice/alsa-audio.h
@@ -57,6 +57,7 @@ typedef struct AlsaData {
     void (*reorder_func)(const void *, void *, int);
     void *reorder_buf;
     int reorder_buf_size; ///< in frames
+    int64_t timestamp; ///< current timestamp, without latency applied.
 } AlsaData;
 
 /**
diff --git a/libavdevice/lavfi.c b/libavdevice/lavfi.c
index 559f721c8f..a177ad0271 100644
--- a/libavdevice/lavfi.c
+++ b/libavdevice/lavfi.c
@@ -248,6 +248,10 @@ av_cold static int lavfi_read_header(AVFormatContext *avctx)
                 ret = av_opt_set_int_list(sink, "sample_fmts", sample_fmts,  AV_SAMPLE_FMT_NONE, AV_OPT_SEARCH_CHILDREN);
             if (ret < 0)
                 goto end;
+            ret = av_opt_set_int(sink, "all_channel_counts", 1,
+                                 AV_OPT_SEARCH_CHILDREN);
+            if (ret < 0)
+                goto end;
         }
 
         lavfi->sinks[i] = sink;
diff --git a/libavfilter/af_aconvert.c b/libavfilter/af_aconvert.c
index 10497aa787..19095cb7e6 100644
--- a/libavfilter/af_aconvert.c
+++ b/libavfilter/af_aconvert.c
@@ -66,7 +66,7 @@ static av_cold int init(AVFilterContext *ctx)
         (ret = ff_parse_sample_format(&aconvert->out_sample_fmt, aconvert->format_str, ctx)) < 0)
         return ret;
     if (aconvert->channel_layout_str && strcmp(aconvert->channel_layout_str, "auto"))
-        return ff_parse_channel_layout(&aconvert->out_chlayout, aconvert->channel_layout_str, ctx);
+        return ff_parse_channel_layout(&aconvert->out_chlayout, NULL, aconvert->channel_layout_str, ctx);
     return ret;
 }
 
diff --git a/libavfilter/af_pan.c b/libavfilter/af_pan.c
index 1a01664675..d28f382482 100644
--- a/libavfilter/af_pan.c
+++ b/libavfilter/af_pan.c
@@ -46,7 +46,6 @@ typedef struct PanContext {
     double gain[MAX_CHANNELS][MAX_CHANNELS];
     int64_t need_renorm;
     int need_renumber;
-    int nb_input_channels;
     int nb_output_channels;
 
     int pure_gains;
@@ -116,10 +115,10 @@ static av_cold int init(AVFilterContext *ctx)
     if (!args)
         return AVERROR(ENOMEM);
     arg = av_strtok(args, "|", &tokenizer);
-    ret = ff_parse_channel_layout(&pan->out_channel_layout, arg, ctx);
+    ret = ff_parse_channel_layout(&pan->out_channel_layout,
+                                  &pan->nb_output_channels, arg, ctx);
     if (ret < 0)
         goto fail;
-    pan->nb_output_channels = av_get_channel_layout_nb_channels(pan->out_channel_layout);
 
     /* parse channel specifications */
     while ((arg = arg0 = av_strtok(NULL, "|", &tokenizer))) {
@@ -239,12 +238,14 @@ static int query_formats(AVFilterContext *ctx)
     ff_set_common_samplerates(ctx, formats);
 
     // inlink supports any channel layout
-    layouts = ff_all_channel_layouts();
+    layouts = ff_all_channel_counts();
     ff_channel_layouts_ref(layouts, &inlink->out_channel_layouts);
 
     // outlink supports only requested output channel layout
     layouts = NULL;
-    ff_add_channel_layout(&layouts, pan->out_channel_layout);
+    ff_add_channel_layout(&layouts,
+                          pan->out_channel_layout ? pan->out_channel_layout :
+                          FF_COUNT2LAYOUT(pan->nb_output_channels));
     ff_channel_layouts_ref(layouts, &outlink->in_channel_layouts);
     return 0;
 }
@@ -257,7 +258,6 @@ static int config_props(AVFilterLink *link)
     int i, j, k, r;
     double t;
 
-    pan->nb_input_channels = av_get_channel_layout_nb_channels(link->channel_layout);
     if (pan->need_renumber) {
         // input channels were given by their name: renumber them
         for (i = j = 0; i < MAX_CHANNELS; i++) {
@@ -271,7 +271,7 @@ static int config_props(AVFilterLink *link)
 
     // sanity check; can't be done in query_formats since the inlink
     // channel layout is unknown at that time
-    if (pan->nb_input_channels > SWR_CH_MAX ||
+    if (link->channels > SWR_CH_MAX ||
         pan->nb_output_channels > SWR_CH_MAX) {
         av_log(ctx, AV_LOG_ERROR,
                "libswresample support a maximum of %d channels. "
@@ -286,6 +286,10 @@ static int config_props(AVFilterLink *link)
                                   0, ctx);
     if (!pan->swr)
         return AVERROR(ENOMEM);
+    if (!link->channel_layout)
+        av_opt_set_int(pan->swr, "ich", link->channels, 0);
+    if (!pan->out_channel_layout)
+        av_opt_set_int(pan->swr, "och", pan->nb_output_channels, 0);
 
     // gains are pure, init the channel mapping
     if (pan->pure_gains) {
@@ -293,7 +297,7 @@ static int config_props(AVFilterLink *link)
         // get channel map from the pure gains
         for (i = 0; i < pan->nb_output_channels; i++) {
             int ch_id = -1;
-            for (j = 0; j < pan->nb_input_channels; j++) {
+            for (j = 0; j < link->channels; j++) {
                 if (pan->gain[i][j]) {
                     ch_id = j;
                     break;
@@ -311,7 +315,7 @@ static int config_props(AVFilterLink *link)
             if (!((pan->need_renorm >> i) & 1))
                 continue;
             t = 0;
-            for (j = 0; j < pan->nb_input_channels; j++)
+            for (j = 0; j < link->channels; j++)
                 t += pan->gain[i][j];
             if (t > -1E-5 && t < 1E-5) {
                 // t is almost 0 but not exactly, this is probably a mistake
@@ -320,7 +324,7 @@ static int config_props(AVFilterLink *link)
                            "Degenerate coefficients while renormalizing\n");
                 continue;
             }
-            for (j = 0; j < pan->nb_input_channels; j++)
+            for (j = 0; j < link->channels; j++)
                 pan->gain[i][j] /= t;
         }
         av_opt_set_int(pan->swr, "icl", link->channel_layout, 0);
@@ -335,7 +339,7 @@ static int config_props(AVFilterLink *link)
     // summary
     for (i = 0; i < pan->nb_output_channels; i++) {
         cur = buf;
-        for (j = 0; j < pan->nb_input_channels; j++) {
+        for (j = 0; j < link->channels; j++) {
             r = snprintf(cur, buf + sizeof(buf) - cur, "%s%.3g i%d",
                          j ? " + " : "", pan->gain[i][j], j);
             cur += FFMIN(buf + sizeof(buf) - cur, r);
diff --git a/libavfilter/asrc_aevalsrc.c b/libavfilter/asrc_aevalsrc.c
index ded533d568..4c1bbdf1f8 100644
--- a/libavfilter/asrc_aevalsrc.c
+++ b/libavfilter/asrc_aevalsrc.c
@@ -109,7 +109,7 @@ static av_cold int init(AVFilterContext *ctx)
 
     if (eval->chlayout_str) {
         int n;
-        ret = ff_parse_channel_layout(&eval->chlayout, eval->chlayout_str, ctx);
+        ret = ff_parse_channel_layout(&eval->chlayout, NULL, eval->chlayout_str, ctx);
         if (ret < 0)
             goto end;
 
diff --git a/libavfilter/asrc_anullsrc.c b/libavfilter/asrc_anullsrc.c
index 26b32e1647..28d4500a25 100644
--- a/libavfilter/asrc_anullsrc.c
+++ b/libavfilter/asrc_anullsrc.c
@@ -68,7 +68,7 @@ static av_cold int init(AVFilterContext *ctx)
                                      null->sample_rate_str, ctx)) < 0)
         return ret;
 
-    if ((ret = ff_parse_channel_layout(&null->channel_layout,
+    if ((ret = ff_parse_channel_layout(&null->channel_layout, NULL,
                                         null->channel_layout_str, ctx)) < 0)
         return ret;
 
diff --git a/libavfilter/avfiltergraph.c b/libavfilter/avfiltergraph.c
index 506d79ec71..1fb83c4877 100644
--- a/libavfilter/avfiltergraph.c
+++ b/libavfilter/avfiltergraph.c
@@ -654,6 +654,10 @@ static int pick_format(AVFilterLink *link, AVFilterLink *ref)
             av_log(link->src, AV_LOG_ERROR, "Cannot select channel layout for"
                    " the link between filters %s and %s.\n", link->src->name,
                    link->dst->name);
+            if (!link->in_channel_layouts->all_counts)
+                av_log(link->src, AV_LOG_ERROR, "Unknown channel layouts not "
+                       "supported, try specifying a channel layout using "
+                       "'aformat=channel_layouts=something'.\n");
             return AVERROR(EINVAL);
         }
         link->in_channel_layouts->nb_channel_layouts = 1;
@@ -737,7 +741,8 @@ static int reduce_formats_on_filter(AVFilterContext *filter)
             if (inlink->type != outlink->type || fmts->nb_channel_layouts == 1)
                 continue;
 
-            if (fmts->all_layouts) {
+            if (fmts->all_layouts &&
+                (!FF_LAYOUT2COUNT(fmt) || fmts->all_counts)) {
                 /* Turn the infinite list into a singleton */
                 fmts->all_layouts = fmts->all_counts  = 0;
                 ff_add_channel_layout(&outlink->in_channel_layouts, fmt);
diff --git a/libavfilter/formats.c b/libavfilter/formats.c
index d51bf3c51d..5816032746 100644
--- a/libavfilter/formats.c
+++ b/libavfilter/formats.c
@@ -615,10 +615,21 @@ int ff_parse_sample_rate(int *ret, const char *arg, void *log_ctx)
     return 0;
 }
 
-int ff_parse_channel_layout(int64_t *ret, const char *arg, void *log_ctx)
+int ff_parse_channel_layout(int64_t *ret, int *nret, const char *arg,
+                            void *log_ctx)
 {
     char *tail;
-    int64_t chlayout = av_get_channel_layout(arg);
+    int64_t chlayout, count;
+
+    if (nret) {
+        count = strtol(arg, &tail, 10);
+        if (*tail == 'c' && !tail[1] && count > 0 && count < 63) {
+            *nret = count;
+            *ret = 0;
+            return 0;
+        }
+    }
+    chlayout = av_get_channel_layout(arg);
     if (chlayout == 0) {
         chlayout = strtol(arg, &tail, 10);
         if (*tail || chlayout == 0) {
@@ -627,6 +638,8 @@ int ff_parse_channel_layout(int64_t *ret, const char *arg, void *log_ctx)
         }
     }
     *ret = chlayout;
+    if (nret)
+        *nret = av_get_channel_layout_nb_channels(chlayout);
     return 0;
 }
 
diff --git a/libavfilter/internal.h b/libavfilter/internal.h
index f8d0cce638..5e19698d07 100644
--- a/libavfilter/internal.h
+++ b/libavfilter/internal.h
@@ -207,11 +207,14 @@ int ff_parse_sample_format(int *ret, const char *arg, void *log_ctx);
  * Parse a channel layout or a corresponding integer representation.
  *
  * @param ret 64bit integer pointer to where the value should be written.
+ * @param nret integer pointer to the number of channels;
+ *             if not NULL, then unknown channel layouts are accepted
  * @param arg string to parse
  * @param log_ctx log context
  * @return >= 0 in case of success, a negative AVERROR code on error
  */
-int ff_parse_channel_layout(int64_t *ret, const char *arg, void *log_ctx);
+int ff_parse_channel_layout(int64_t *ret, int *nret, const char *arg,
+                            void *log_ctx);
 
 void ff_update_link_current_pts(AVFilterLink *link, int64_t pts);
 
diff --git a/libavformat/wavenc.c b/libavformat/wavenc.c
index fea38cf326..0067dfef29 100644
--- a/libavformat/wavenc.c
+++ b/libavformat/wavenc.c
@@ -116,6 +116,11 @@ static int wav_write_header(AVFormatContext *s)
     AVIOContext *pb = s->pb;
     int64_t fmt;
 
+    if (s->nb_streams != 1) {
+        av_log(s, AV_LOG_ERROR, "WAVE files have exactly one stream\n");
+        return AVERROR(EINVAL);
+    }
+
     if (wav->rf64 == RF64_ALWAYS) {
         ffio_wfourcc(pb, "RF64");
         avio_wl32(pb, -1); /* RF64 chunk size: use size in ds64 */
diff --git a/libswresample/rematrix.c b/libswresample/rematrix.c
index 5c98e68990..e146edfcf7 100644
--- a/libswresample/rematrix.c
+++ b/libswresample/rematrix.c
@@ -433,8 +433,8 @@ int swri_rematrix(SwrContext *s, AudioData *out, AudioData *in, int len, int mus
         off = len1 * out->bps;
     }
 
-    av_assert0(out->ch_count == av_get_channel_layout_nb_channels(s->out_ch_layout));
-    av_assert0(in ->ch_count == av_get_channel_layout_nb_channels(s-> in_ch_layout));
+    av_assert0(!s->out_ch_layout || out->ch_count == av_get_channel_layout_nb_channels(s->out_ch_layout));
+    av_assert0(!s-> in_ch_layout || in ->ch_count == av_get_channel_layout_nb_channels(s-> in_ch_layout));
 
     for(out_i=0; out_i<out->ch_count; out_i++){
         switch(s->matrix_ch[out_i][0]){