mlp: implement support for AVCodecContext.request_channel_layout.

Also wrap usage of AVCodecContext.request_channels in FF_API_REQUEST_CHANNELS directives.
Signed-off-by: Justin Ruggles <justin.ruggles@gmail.com>

libavcodec/mlp_parser.c

@@ -322,28 +322,45 @@ static int mlp_parse(AVCodecParserContext *s,
 
         if (mh.stream_type == 0xbb) {
             /* MLP stream */
+#if FF_API_REQUEST_CHANNELS
             if (avctx->request_channels > 0 && avctx->request_channels <= 2 &&
                 mh.num_substreams > 1) {
                 avctx->channels       = 2;
                 avctx->channel_layout = AV_CH_LAYOUT_STEREO;
+            } else
+#endif
+            if (avctx->request_channel_layout == AV_CH_LAYOUT_STEREO &&
+                mh.num_substreams > 1) {
+                avctx->channels       = 2;
+                avctx->channel_layout = AV_CH_LAYOUT_STEREO;
             } else {
                 avctx->channels       = mh.channels_mlp;
                 avctx->channel_layout = mh.channel_layout_mlp;
             }
         } else { /* mh.stream_type == 0xba */
             /* TrueHD stream */
+#if FF_API_REQUEST_CHANNELS
             if (avctx->request_channels > 0 && avctx->request_channels <= 2 &&
                 mh.num_substreams > 1) {
                 avctx->channels       = 2;
                 avctx->channel_layout = AV_CH_LAYOUT_STEREO;
-            } else if (mh.channels_thd_stream2 &&
-                       (avctx->request_channels <= 0 ||
-                        avctx->request_channels > mh.channels_thd_stream1)) {
-                avctx->channels       = mh.channels_thd_stream2;
-                avctx->channel_layout = mh.channel_layout_thd_stream2;
-            } else {
+            } else if (avctx->request_channels > 0 &&
+                       avctx->request_channels <= mh.channels_thd_stream1) {
+                avctx->channels       = mh.channels_thd_stream1;
+                avctx->channel_layout = mh.channel_layout_thd_stream1;
+            } else
+#endif
+            if (avctx->request_channel_layout == AV_CH_LAYOUT_STEREO &&
+                mh.num_substreams > 1) {
+                avctx->channels       = 2;
+                avctx->channel_layout = AV_CH_LAYOUT_STEREO;
+            } else if (avctx->request_channel_layout == mh.channel_layout_thd_stream1 ||
+                       !mh.channels_thd_stream2) {
                 avctx->channels       = mh.channels_thd_stream1;
                 avctx->channel_layout = mh.channel_layout_thd_stream1;
+            } else {
+                avctx->channels       = mh.channels_thd_stream2;
+                avctx->channel_layout = mh.channel_layout_thd_stream2;
             }
         }
 

libavcodec/mlpdec.c

@@ -445,14 +445,24 @@ static int read_restart_header(MLPDecodeContext *m, GetBitContext *gbp,
         return AVERROR_INVALIDDATA;
     }
 
-    if (m->avctx->request_channels > 0
-        && s->max_channel + 1 >= m->avctx->request_channels
-        && substr < m->max_decoded_substream) {
+#if FF_API_REQUEST_CHANNELS
+    if (m->avctx->request_channels > 0 &&
+        m->avctx->request_channels <= s->max_channel + 1 &&
+        m->max_decoded_substream > substr) {
         av_log(m->avctx, AV_LOG_DEBUG,
-               "Extracting %d channel downmix from substream %d. "
+               "Extracting %d-channel downmix from substream %d. "
                "Further substreams will be skipped.\n",
                s->max_channel + 1, substr);
         m->max_decoded_substream = substr;
+    } else
+#endif
+    if (m->avctx->request_channel_layout == s->ch_layout &&
+        m->max_decoded_substream > substr) {
+        av_log(m->avctx, AV_LOG_DEBUG,
+               "Extracting %d-channel downmix (0x%"PRIx64") from substream %d. "
+               "Further substreams will be skipped.\n",
+               s->max_channel + 1, s->ch_layout, substr);
+        m->max_decoded_substream = substr;
     }
 
     s->noise_shift   = get_bits(gbp,  4);