Reduce redundancy when SILK uses too many bits

Fix Hybrid redundancy assertion failure in ec_enc_shrink(), even
if SILK produces more than maxBits, by reducing or eliminating
redundancy when necessary.  Don't reserve space for redundancy that
is too small to be used for redundancy.  When there is not enough
space for redundancy, allow the regular frame to use all the bits.

2 files changed, 45 insertions, 24 deletions

diff --git a/src/opus_encoder.c b/src/opus_encoder.c
index 974bd129..b5f739c9 100644
--- a/src/opus_encoder.c
+++ b/src/opus_encoder.c
@@ -1961,7 +1961,6 @@ opus_int32 opus_encode_native(OpusEncoder *st, const opus_val16 *pcm, int frame_
               st->silk_mode.bitRate += 3*rate_offset/5;
            else
               st->silk_mode.bitRate += rate_offset;
-           bytes_target += rate_offset * frame_size / (8 * st->Fs);
         }
 
         st->silk_mode.payloadSize_ms = 1000 * frame_size / st->Fs;
@@ -2005,11 +2004,11 @@ opus_int32 opus_encode_native(OpusEncoder *st, const opus_val16 *pcm, int frame_
         /* Call SILK encoder for the low band */
 
         /* Max bits for SILK, counting ToC, redundancy bytes, and optionally redundancy. */
-        st->silk_mode.maxBits = IMIN(1275, max_data_bytes-1-redundancy_bytes)*8;
-        if (redundancy)
+        st->silk_mode.maxBits = (max_data_bytes-1)*8;
+        if (redundancy && redundancy_bytes >= 2)
         {
            /* Counting 1 bit for redundancy position and 20 bits for flag+size (only for hybrid). */
-           st->silk_mode.maxBits -= 1;
+           st->silk_mode.maxBits -= redundancy_bytes*8 + 1;
            if (st->mode == MODE_HYBRID)
               st->silk_mode.maxBits -= 20;
         }
@@ -2134,18 +2133,9 @@ opus_int32 opus_encode_native(OpusEncoder *st, const opus_val16 *pcm, int frame_
 
         if (st->mode == MODE_HYBRID)
         {
-            int len;
-
-            len = (ec_tell(&enc)+7)>>3;
-            if (redundancy)
-               len += st->mode == MODE_HYBRID ? 3 : 1;
             if( st->use_vbr ) {
                 celt_encoder_ctl(celt_enc, OPUS_SET_BITRATE(st->bitrate_bps-st->silk_mode.bitRate));
-                nb_compr_bytes = max_data_bytes-1-redundancy_bytes;
                 celt_encoder_ctl(celt_enc, OPUS_SET_VBR_CONSTRAINT(0));
-            } else {
-                /* check if SILK used up too much */
-                nb_compr_bytes = len > bytes_target ? len : bytes_target;
             }
         } else {
             if (st->use_vbr)
@@ -2162,14 +2152,8 @@ opus_int32 opus_encode_native(OpusEncoder *st, const opus_val16 *pcm, int frame_
                 celt_encoder_ctl(celt_enc, OPUS_SET_VBR(1));
                 celt_encoder_ctl(celt_enc, OPUS_SET_VBR_CONSTRAINT(st->vbr_constraint));
                 celt_encoder_ctl(celt_enc, OPUS_SET_BITRATE(st->bitrate_bps+bonus));
-                nb_compr_bytes = max_data_bytes-1-redundancy_bytes;
-            } else {
-                nb_compr_bytes = bytes_target;
             }
         }
-
-    } else {
-        nb_compr_bytes = 0;
     }
 
     ALLOC(tmp_prefill, st->channels*st->Fs/400, opus_val16);
@@ -2218,14 +2202,19 @@ opus_int32 opus_encode_native(OpusEncoder *st, const opus_val16 *pcm, int frame_
     if ( st->mode != MODE_CELT_ONLY && ec_tell(&enc)+17+20*(st->mode == MODE_HYBRID) <= 8*(max_data_bytes-1))
     {
         /* For SILK mode, the redundancy is inferred from the length */
-        if (st->mode == MODE_HYBRID && (redundancy || ec_tell(&enc)+37 <= 8*nb_compr_bytes))
+        if (st->mode == MODE_HYBRID)
            ec_enc_bit_logp(&enc, redundancy, 12);
         if (redundancy)
         {
             int max_redundancy;
             ec_enc_bit_logp(&enc, celt_to_silk, 1);
             if (st->mode == MODE_HYBRID)
-               max_redundancy = (max_data_bytes-1)-nb_compr_bytes;
+            {
+               /* Reserve the 8 bits needed for the redundancy length,
+                  and at least a few bits for CELT if possible */
+               max_redundancy = (max_data_bytes-1)-((ec_tell(&enc)+8+3+7)>>3);
+               max_redundancy = IMIN(max_redundancy, redundancy_bytes);
+            }
             else
                max_redundancy = (max_data_bytes-1)-((ec_tell(&enc)+7)>>3);
             /* Target the same bit-rate for redundancy as for the rest,
@@ -2252,7 +2241,7 @@ opus_int32 opus_encode_native(OpusEncoder *st, const opus_val16 *pcm, int frame_
         ec_enc_done(&enc);
         nb_compr_bytes = ret;
     } else {
-       nb_compr_bytes = IMIN((max_data_bytes-1)-redundancy_bytes, nb_compr_bytes);
+       nb_compr_bytes = (max_data_bytes-1)-redundancy_bytes;
        ec_enc_shrink(&enc, nb_compr_bytes);
     }
 
@@ -2299,7 +2288,7 @@ opus_int32 opus_encode_native(OpusEncoder *st, const opus_val16 *pcm, int frame_
            celt_encode_with_ec(celt_enc, tmp_prefill, st->Fs/400, dummy, 2, NULL);
            celt_encoder_ctl(celt_enc, CELT_SET_PREDICTION(0));
         }
-        /* If false, we already busted the budget and we'll end up with a "PLC packet" */
+        /* If false, we already busted the budget and we'll end up with a "PLC frame" */
         if (ec_tell(&enc) <= 8*nb_compr_bytes)
         {
            /* Set the bitrate again if it was overridden in the redundancy code above*/
@@ -2413,7 +2402,6 @@ opus_int32 opus_encode_native(OpusEncoder *st, const opus_val16 *pcm, int frame_
     if (!st->use_vbr)
     {
        if (opus_packet_pad(data, ret, max_data_bytes) != OPUS_OK)
-
        {
           RESTORE_STACK;
           return OPUS_INTERNAL_ERROR;
diff --git a/tests/opus_encode_regressions.c b/tests/opus_encode_regressions.c
index 2bc76491..aaeaf1e8 100644
--- a/tests/opus_encode_regressions.c
+++ b/tests/opus_encode_regressions.c
@@ -951,6 +951,38 @@ static int ec_enc_shrink_assert(void)
     return 0;
 }
 
+static int ec_enc_shrink_assert2(void)
+{
+    OpusEncoder *enc;
+    int err;
+    int data_len;
+    unsigned char data[2000];
+
+    enc = opus_encoder_create(48000, 1, OPUS_APPLICATION_AUDIO, &err);
+    opus_encoder_ctl(enc, OPUS_SET_COMPLEXITY(6));
+    opus_encoder_ctl(enc, OPUS_SET_SIGNAL(OPUS_SIGNAL_VOICE));
+    opus_encoder_ctl(enc, OPUS_SET_BANDWIDTH(OPUS_BANDWIDTH_FULLBAND));
+    opus_encoder_ctl(enc, OPUS_SET_PACKET_LOSS_PERC(26));
+    opus_encoder_ctl(enc, OPUS_SET_BITRATE(27000));
+    {
+        static const short pcm[960] = { 0 };
+        data_len = opus_encode(enc, pcm, 960, data, 2000);
+        assert(data_len > 0);
+    }
+    opus_encoder_ctl(enc, OPUS_SET_SIGNAL(OPUS_SIGNAL_MUSIC));
+    {
+        static const short pcm[480] =
+        {
+            32767, 32767, 0, 0, 32767, 32767, 0, 0, 32767, 32767,
+            -32768, -32768, 0, 0, -32768, -32768, 0, 0, -32768, -32768
+        };
+        data_len = opus_encode(enc, pcm, 480, data, 19);
+        assert(data_len > 0);
+    }
+    opus_encoder_destroy(enc);
+    return 0;
+}
+
 void regression_test(void)
 {
    fprintf(stderr, "Running simple tests for bugs that have been fixed previously\n");
@@ -959,4 +991,5 @@ void regression_test(void)
    mscbr_encode_fail();
    surround_analysis_uninit();
    ec_enc_shrink_assert();
+   ec_enc_shrink_assert2();
 }