eac3enc: use different numbers of blocks per frame to allow higher bitrates

1 files changed, 22 insertions, 8 deletions

diff --git a/libavcodec/eac3enc.c b/libavcodec/eac3enc.c
index 09fa80fcb9..038aa2a234 100644
--- a/libavcodec/eac3enc.c
+++ b/libavcodec/eac3enc.c
@@ -63,6 +63,11 @@ void ff_eac3_get_frame_exp_strategy(AC3EncodeContext *s)
 {
     int ch;
 
+    if (s->num_blocks < 6) {
+        s->use_frame_exp_strategy = 0;
+        return;
+    }
+
     s->use_frame_exp_strategy = 1;
     for (ch = !s->cpl_on; ch <= s->fbw_channels; ch++) {
         int expstr = eac3_frame_expstr_index_tab[s->exp_strategy[ch][0]-1]
@@ -89,7 +94,7 @@ void ff_eac3_set_cpl_states(AC3EncodeContext *s)
     /* set first cpl coords */
     for (ch = 1; ch <= s->fbw_channels; ch++)
         first_cpl_coords[ch] = 1;
-    for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
+    for (blk = 0; blk < s->num_blocks; blk++) {
         AC3Block *block = &s->blocks[blk];
         for (ch = 1; ch <= s->fbw_channels; ch++) {
             if (block->channel_in_cpl[ch]) {
@@ -104,7 +109,7 @@ void ff_eac3_set_cpl_states(AC3EncodeContext *s)
     }
 
     /* set first cpl leak */
-    for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
+    for (blk = 0; blk < s->num_blocks; blk++) {
         AC3Block *block = &s->blocks[blk];
         if (block->cpl_in_use) {
             block->new_cpl_leak = 2;
@@ -130,7 +135,7 @@ void ff_eac3_output_frame_header(AC3EncodeContext *s)
         put_bits(&s->pb, 2, s->bit_alloc.sr_code);  /* sample rate code */
     } else {
         put_bits(&s->pb, 2, s->bit_alloc.sr_code);  /* sample rate code */
-        put_bits(&s->pb, 2, 0x3);                   /* number of blocks = 6 */
+        put_bits(&s->pb, 2, s->num_blks_code);      /* number of blocks */
     }
     put_bits(&s->pb, 3, s->channel_mode);           /* audio coding mode */
     put_bits(&s->pb, 1, s->lfe_on);                 /* LFE channel indicator */
@@ -141,11 +146,15 @@ void ff_eac3_output_frame_header(AC3EncodeContext *s)
     /* TODO: mixing metadata */
     put_bits(&s->pb, 1, 0);                         /* no info metadata */
     /* TODO: info metadata */
+    if (s->num_blocks != 6)
+        put_bits(&s->pb, 1, !(s->avctx->frame_number % 6)); /* converter sync flag */
     put_bits(&s->pb, 1, 0);                         /* no additional bit stream info */
 
     /* frame header */
+    if (s->num_blocks == 6) {
     put_bits(&s->pb, 1, !s->use_frame_exp_strategy);/* exponent strategy syntax */
     put_bits(&s->pb, 1, 0);                         /* aht enabled = no */
+    }
     put_bits(&s->pb, 2, 0);                         /* snr offset strategy = 1 */
     put_bits(&s->pb, 1, 0);                         /* transient pre-noise processing enabled = no */
     put_bits(&s->pb, 1, 0);                         /* block switch syntax enabled = no */
@@ -158,7 +167,7 @@ void ff_eac3_output_frame_header(AC3EncodeContext *s)
     /* coupling strategy use flags */
     if (s->channel_mode > AC3_CHMODE_MONO) {
         put_bits(&s->pb, 1, s->blocks[0].cpl_in_use);
-        for (blk = 1; blk < AC3_MAX_BLOCKS; blk++) {
+        for (blk = 1; blk < s->num_blocks; blk++) {
             AC3Block *block = &s->blocks[blk];
             put_bits(&s->pb, 1, block->new_cpl_strategy);
             if (block->new_cpl_strategy)
@@ -170,26 +179,31 @@ void ff_eac3_output_frame_header(AC3EncodeContext *s)
         for (ch = !s->cpl_on; ch <= s->fbw_channels; ch++)
             put_bits(&s->pb, 5, s->frame_exp_strategy[ch]);
     } else {
-        for (blk = 0; blk < AC3_MAX_BLOCKS; blk++)
+        for (blk = 0; blk < s->num_blocks; blk++)
             for (ch = !s->blocks[blk].cpl_in_use; ch <= s->fbw_channels; ch++)
                 put_bits(&s->pb, 2, s->exp_strategy[ch][blk]);
     }
     if (s->lfe_on) {
-        for (blk = 0; blk < AC3_MAX_BLOCKS; blk++)
+        for (blk = 0; blk < s->num_blocks; blk++)
             put_bits(&s->pb, 1, s->exp_strategy[s->lfe_channel][blk]);
     }
-    /* E-AC-3 to AC-3 converter exponent strategy (unfortunately not optional...) */
+    /* E-AC-3 to AC-3 converter exponent strategy (not optional when num blocks == 6) */
+    if (s->num_blocks != 6) {
+        put_bits(&s->pb, 1, 0);
+    } else {
     for (ch = 1; ch <= s->fbw_channels; ch++) {
         if (s->use_frame_exp_strategy)
             put_bits(&s->pb, 5, s->frame_exp_strategy[ch]);
         else
             put_bits(&s->pb, 5, 0);
     }
+    }
     /* snr offsets */
     put_bits(&s->pb, 6, s->coarse_snr_offset);
     put_bits(&s->pb, 4, s->fine_snr_offset[1]);
     /* block start info */
-    put_bits(&s->pb, 1, 0);
+    if (s->num_blocks > 1)
+        put_bits(&s->pb, 1, 0);
 }