opusdec: do not fail when LBRR frames are present

Decode and discard them.

Fixes ticket 4641.

libavcodec/opus_silk.c

@@ -506,7 +506,8 @@ static inline void silk_decode_excitation(SilkContext *s, OpusRangeCoder *rc,
 #define LTP_ORDER 5
 
 static void silk_decode_frame(SilkContext *s, OpusRangeCoder *rc,
-                              int frame_num, int channel, int coded_channels, int active, int active1)
+                              int frame_num, int channel, int coded_channels,
+                              int active, int active1, int redundant)
 {
     /* per frame */
     int voiced;       // combines with active to indicate inactive, active, or active+voiced
@@ -665,8 +666,9 @@ static void silk_decode_frame(SilkContext *s, OpusRangeCoder *rc,
     silk_decode_excitation(s, rc, residual + SILK_MAX_LAG, qoffset_high,
                            active, voiced);
 
-    /* skip synthesising the side channel if we want mono-only */
-    if (s->output_channels == channel)
+    /* skip synthesising the output if we do not need it */
+    // TODO: implement error recovery
+    if (s->output_channels == channel || redundant)
         return;
 
     /* generate the output signal */
@@ -814,15 +816,27 @@ int ff_silk_decode_superframe(SilkContext *s, OpusRangeCoder *rc,
             active[i][j] = ff_opus_rc_dec_log(rc, 1);
 
         redundancy[i] = ff_opus_rc_dec_log(rc, 1);
-        if (redundancy[i]) {
-            avpriv_report_missing_feature(s->avctx, "LBRR frames");
-            return AVERROR_PATCHWELCOME;
+    }
+
+    /* read the per-frame LBRR flags */
+    for (i = 0; i < coded_channels; i++)
+        if (redundancy[i] && duration_ms > 20) {
+            redundancy[i] = ff_opus_rc_dec_cdf(rc, duration_ms == 40 ?
+                                                   ff_silk_model_lbrr_flags_40 : ff_silk_model_lbrr_flags_60);
         }
+
+    /* decode the LBRR frames */
+    for (i = 0; i < nb_frames; i++) {
+        for (j = 0; j < coded_channels; j++)
+            if (redundancy[j] & (1 << i)) {
+                int active1 = (j == 0 && !(redundancy[1] & (1 << i))) ? 0 : 1;
+                silk_decode_frame(s, rc, i, j, coded_channels, 1, active1, 1);
+            }
     }
 
     for (i = 0; i < nb_frames; i++) {
         for (j = 0; j < coded_channels && !s->midonly; j++)
-            silk_decode_frame(s, rc, i, j, coded_channels, active[j][i], active[1][i]);
+            silk_decode_frame(s, rc, i, j, coded_channels, active[j][i], active[1][i], 0);
 
         /* reset the side channel if it is not coded */
         if (s->midonly && s->frame[1].coded)

libavcodec/opustab.c

@@ -26,6 +26,9 @@ const uint8_t ff_opus_default_coupled_streams[] = { 0, 1, 1, 2, 2, 2, 2, 3 };
 
 const uint8_t ff_celt_band_end[] = { 13, 17, 17, 19, 21 };
 
+const uint16_t ff_silk_model_lbrr_flags_40[] = { 256, 0, 53, 106, 256 };
+const uint16_t ff_silk_model_lbrr_flags_60[] = { 256, 0, 41, 61, 90, 131, 146, 174, 256 };
+
 const uint16_t ff_silk_model_stereo_s1[] = {
     256,   7,   9,  10,  11,  12,  22,  46,  54,  55,  56,  59,  82, 174, 197, 200,
     201, 202, 210, 234, 244, 245, 246, 247, 249, 256

libavcodec/opustab.h

@@ -31,6 +31,9 @@ extern const uint8_t  ff_celt_band_end[];
 
 extern const uint8_t  ff_opus_default_coupled_streams[];
 
+extern const uint16_t ff_silk_model_lbrr_flags_40[];
+extern const uint16_t ff_silk_model_lbrr_flags_60[];
+
 extern const uint16_t ff_silk_model_stereo_s1[];
 extern const uint16_t ff_silk_model_stereo_s2[];
 extern const uint16_t ff_silk_model_stereo_s3[];