aacdec: More robust output configuration.

Save the old output configuration (if it has been used
successfully) when trying a new configuration. If the new configuration
fails to decode, restore the last successful configuration.

libavcodec/aac.h

@@ -112,6 +112,15 @@ enum OCStatus {
     OC_LOCKED,      ///< Output configuration locked in place
 };
 
+typedef struct {
+    MPEG4AudioConfig m4ac;
+    uint8_t layout_map[MAX_ELEM_ID*4][3];
+    int layout_map_tags;
+    int channels;
+    uint64_t channel_layout;
+    enum OCStatus status;
+} OutputConfiguration;
+
 /**
  * Predictor State
  */
@@ -254,8 +263,6 @@ typedef struct {
     AVCodecContext *avctx;
     AVFrame frame;
 
-    MPEG4AudioConfig m4ac;
-
     int is_saved;                 ///< Set if elements have stored overlap from previous frame.
     DynamicRangeControl che_drc;
 
@@ -263,8 +270,6 @@ typedef struct {
      * @name Channel element related data
      * @{
      */
-    uint8_t layout_map[MAX_ELEM_ID*4][3];
-    int layout_map_tags;
     ChannelElement          *che[4][MAX_ELEM_ID];
     ChannelElement  *tag_che_map[4][MAX_ELEM_ID];
     int tags_mapped;
@@ -299,7 +304,7 @@ typedef struct {
 
     DECLARE_ALIGNED(32, float, temp)[128];
 
-    enum OCStatus output_configured;
+    OutputConfiguration oc[2];
 } AACContext;
 
 #endif /* AVCODEC_AAC_H */

libavcodec/aacsbr.c

@@ -914,7 +914,7 @@ static void read_sbr_extension(AACContext *ac, SpectralBandReplication *sbr,
 {
     switch (bs_extension_id) {
     case EXTENSION_ID_PS:
-        if (!ac->m4ac.ps) {
+        if (!ac->oc[1].m4ac.ps) {
             av_log(ac->avctx, AV_LOG_ERROR, "Parametric Stereo signaled to be not-present but was found in the bitstream.\n");
             skip_bits_long(gb, *num_bits_left); // bs_fill_bits
             *num_bits_left = 0;
@@ -1071,9 +1071,9 @@ int ff_decode_sbr_extension(AACContext *ac, SpectralBandReplication *sbr,
     sbr->reset = 0;
 
     if (!sbr->sample_rate)
-        sbr->sample_rate = 2 * ac->m4ac.sample_rate; //TODO use the nominal sample rate for arbitrary sample rate support
-    if (!ac->m4ac.ext_sample_rate)
-        ac->m4ac.ext_sample_rate = 2 * ac->m4ac.sample_rate;
+        sbr->sample_rate = 2 * ac->oc[1].m4ac.sample_rate; //TODO use the nominal sample rate for arbitrary sample rate support
+    if (!ac->oc[1].m4ac.ext_sample_rate)
+        ac->oc[1].m4ac.ext_sample_rate = 2 * ac->oc[1].m4ac.sample_rate;
 
     if (crc) {
         skip_bits(gb, 10); // bs_sbr_crc_bits; TODO - implement CRC check
@@ -1648,7 +1648,7 @@ static void sbr_hf_assemble(float Y1[38][64][2],
 void ff_sbr_apply(AACContext *ac, SpectralBandReplication *sbr, int id_aac,
                   float* L, float* R)
 {
-    int downsampled = ac->m4ac.ext_sample_rate < sbr->sample_rate;
+    int downsampled = ac->oc[1].m4ac.ext_sample_rate < sbr->sample_rate;
     int ch;
     int nch = (id_aac == TYPE_CPE) ? 2 : 1;
     int err;
@@ -1695,7 +1695,7 @@ void ff_sbr_apply(AACContext *ac, SpectralBandReplication *sbr, int id_aac,
                   sbr->X_low, ch);
     }
 
-    if (ac->m4ac.ps == 1) {
+    if (ac->oc[1].m4ac.ps == 1) {
         if (sbr->ps.start) {
             ff_ps_apply(ac->avctx, &sbr->ps, sbr->X[0], sbr->X[1], sbr->kx[1] + sbr->m[1]);
         } else {