avconv: check for an incompatible changing channel layout

The decoder can change the layout and channel count during decoding,
but currently we only validate that the two are compatible when opening
the codec. This checks for incompatibilities after each decoded frame.

avconv.c

@@ -1191,6 +1191,58 @@ static int check_recording_time(OutputStream *ost)
     return 1;
 }
 
+static void get_default_channel_layouts(OutputStream *ost, InputStream *ist)
+{
+    char layout_name[256];
+    AVCodecContext *enc = ost->st->codec;
+    AVCodecContext *dec = ist->st->codec;
+
+    if (dec->channel_layout &&
+        av_get_channel_layout_nb_channels(dec->channel_layout) != dec->channels) {
+        av_get_channel_layout_string(layout_name, sizeof(layout_name),
+                                     dec->channels, dec->channel_layout);
+        av_log(NULL, AV_LOG_ERROR, "New channel layout (%s) is invalid\n",
+               layout_name);
+        dec->channel_layout = 0;
+    }
+    if (!dec->channel_layout) {
+        if (enc->channel_layout && dec->channels == enc->channels) {
+            dec->channel_layout = enc->channel_layout;
+        } else {
+            dec->channel_layout = av_get_default_channel_layout(dec->channels);
+
+            if (!dec->channel_layout) {
+                av_log(NULL, AV_LOG_FATAL, "Unable to find default channel "
+                       "layout for Input Stream #%d.%d\n", ist->file_index,
+                       ist->st->index);
+                exit_program(1);
+            }
+        }
+        av_get_channel_layout_string(layout_name, sizeof(layout_name),
+                                     dec->channels, dec->channel_layout);
+        av_log(NULL, AV_LOG_WARNING, "Guessed Channel Layout for  Input Stream "
+               "#%d.%d : %s\n", ist->file_index, ist->st->index, layout_name);
+    }
+    if (!enc->channel_layout) {
+        if (dec->channels == enc->channels) {
+            enc->channel_layout = dec->channel_layout;
+            return;
+        } else {
+            enc->channel_layout = av_get_default_channel_layout(enc->channels);
+        }
+        if (!enc->channel_layout) {
+            av_log(NULL, AV_LOG_FATAL, "Unable to find default channel layout "
+                   "for Output Stream #%d.%d\n", ost->file_index,
+                   ost->st->index);
+            exit_program(1);
+        }
+        av_get_channel_layout_string(layout_name, sizeof(layout_name),
+                                     enc->channels, enc->channel_layout);
+        av_log(NULL, AV_LOG_WARNING, "Guessed Channel Layout for Output Stream "
+               "#%d.%d : %s\n", ost->file_index, ost->st->index, layout_name);
+    }
+}
+
 static void generate_silence(uint8_t* buf, enum AVSampleFormat sample_fmt, size_t size)
 {
     int fill_char = 0x00;
@@ -1301,6 +1353,8 @@ static void do_audio_out(AVFormatContext *s, OutputStream *ost,
     uint8_t *buf = decoded_frame->data[0];
     int size     = decoded_frame->nb_samples * dec->channels * isize;
 
+    get_default_channel_layouts(ost, ist);
+
     if (alloc_audio_output_buf(dec, enc, decoded_frame->nb_samples) < 0) {
         av_log(NULL, AV_LOG_FATAL, "Error allocating audio buffer\n");
         exit_program(1);
@@ -2430,51 +2484,6 @@ static void print_sdp(void)
     av_freep(&avc);
 }
 
-static void get_default_channel_layouts(OutputStream *ost, InputStream *ist)
-{
-    char layout_name[256];
-    AVCodecContext *enc = ost->st->codec;
-    AVCodecContext *dec = ist->st->codec;
-
-    if (!dec->channel_layout) {
-        if (enc->channel_layout && dec->channels == enc->channels) {
-            dec->channel_layout = enc->channel_layout;
-        } else {
-            dec->channel_layout = av_get_default_channel_layout(dec->channels);
-
-            if (!dec->channel_layout) {
-                av_log(NULL, AV_LOG_FATAL, "Unable to find default channel "
-                       "layout for Input Stream #%d.%d\n", ist->file_index,
-                       ist->st->index);
-                exit_program(1);
-            }
-        }
-        av_get_channel_layout_string(layout_name, sizeof(layout_name),
-                                     dec->channels, dec->channel_layout);
-        av_log(NULL, AV_LOG_WARNING, "Guessed Channel Layout for  Input Stream "
-               "#%d.%d : %s\n", ist->file_index, ist->st->index, layout_name);
-    }
-    if (!enc->channel_layout) {
-        if (dec->channels == enc->channels) {
-            enc->channel_layout = dec->channel_layout;
-            return;
-        } else {
-            enc->channel_layout = av_get_default_channel_layout(enc->channels);
-        }
-        if (!enc->channel_layout) {
-            av_log(NULL, AV_LOG_FATAL, "Unable to find default channel layout "
-                   "for Output Stream #%d.%d\n", ost->file_index,
-                   ost->st->index);
-            exit_program(1);
-        }
-        av_get_channel_layout_string(layout_name, sizeof(layout_name),
-                                     enc->channels, enc->channel_layout);
-        av_log(NULL, AV_LOG_WARNING, "Guessed Channel Layout for Output Stream "
-               "#%d.%d : %s\n", ost->file_index, ost->st->index, layout_name);
-    }
-}
-
-
 static int init_input_stream(int ist_index, char *error, int error_len)
 {
     int i;