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

libavcodec/ac3enc.h

@@ -151,6 +151,8 @@ typedef struct AC3EncodeContext {
     int bit_rate;                           ///< target bit rate, in bits-per-second
     int sample_rate;                        ///< sampling frequency, in Hz
 
+    int num_blks_code;                      ///< number of blocks code                  (numblkscod)
+    int num_blocks;                         ///< number of blocks per frame
     int frame_size_min;                     ///< minimum frame size in case rounding is necessary
     int frame_size;                         ///< current frame size in bytes
     int frame_size_code;                    ///< frame size code                        (frmsizecod)

libavcodec/ac3enc_fixed.c

@@ -93,7 +93,7 @@ static void scale_coefficients(AC3EncodeContext *s)
 {
     int blk, ch;
 
-    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->channels; ch++) {
             s->ac3dsp.ac3_rshift_int32(block->mdct_coef[ch], AC3_MAX_COEFS,

libavcodec/ac3enc_float.c

@@ -103,7 +103,7 @@ static int normalize_samples(AC3EncodeContext *s)
  */
 static void scale_coefficients(AC3EncodeContext *s)
 {
-    int chan_size = AC3_MAX_COEFS * AC3_MAX_BLOCKS;
+    int chan_size = AC3_MAX_COEFS * s->num_blocks;
     s->ac3dsp.float_to_fixed24(s->fixed_coef_buffer + chan_size,
                                s->mdct_coef_buffer  + chan_size,
                                chan_size * s->channels);

libavcodec/ac3enc_template.c

@@ -79,13 +79,13 @@ static void deinterleave_input_samples(AC3EncodeContext *s,
         int sinc;
 
         /* copy last 256 samples of previous frame to the start of the current frame */
-        memcpy(&s->planar_samples[ch][0], &s->planar_samples[ch][AC3_FRAME_SIZE],
+        memcpy(&s->planar_samples[ch][0], &s->planar_samples[ch][AC3_BLOCK_SIZE * s->num_blocks],
                AC3_BLOCK_SIZE * sizeof(s->planar_samples[0][0]));
 
         /* deinterleave */
         sinc = s->channels;
         sptr = samples + s->channel_map[ch];
-        for (i = AC3_BLOCK_SIZE; i < AC3_FRAME_SIZE+AC3_BLOCK_SIZE; i++) {
+        for (i = AC3_BLOCK_SIZE; i < AC3_BLOCK_SIZE * (s->num_blocks + 1); i++) {
             s->planar_samples[ch][i] = *sptr;
             sptr += sinc;
         }
@@ -103,7 +103,7 @@ static void apply_mdct(AC3EncodeContext *s)
     int blk, ch;
 
     for (ch = 0; ch < s->channels; ch++) {
-        for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
+        for (blk = 0; blk < s->num_blocks; blk++) {
             AC3Block *block = &s->blocks[blk];
             const SampleType *input_samples = &s->planar_samples[ch][blk * AC3_BLOCK_SIZE];
 
@@ -159,7 +159,7 @@ static void apply_channel_coupling(AC3EncodeContext *s)
     cpl_start     = FFMIN(256, cpl_start + num_cpl_coefs) - num_cpl_coefs;
 
     /* calculate coupling channel from fbw channels */
-    for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
+    for (blk = 0; blk < s->num_blocks; blk++) {
         AC3Block *block = &s->blocks[blk];
         CoefType *cpl_coef = &block->mdct_coef[CPL_CH][cpl_start];
         if (!block->cpl_in_use)
@@ -188,7 +188,7 @@ static void apply_channel_coupling(AC3EncodeContext *s)
     while (i < s->cpl_end_freq) {
         int band_size = s->cpl_band_sizes[bnd];
         for (ch = CPL_CH; ch <= s->fbw_channels; ch++) {
-            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 || (ch > CPL_CH && !block->channel_in_cpl[ch]))
                     continue;
@@ -203,7 +203,7 @@ static void apply_channel_coupling(AC3EncodeContext *s)
     }
 
     /* determine which blocks to send new coupling coordinates for */
-    for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
+    for (blk = 0; blk < s->num_blocks; blk++) {
         AC3Block *block  = &s->blocks[blk];
         AC3Block *block0 = blk ? &s->blocks[blk-1] : NULL;
         int new_coords = 0;
@@ -261,7 +261,7 @@ static void apply_channel_coupling(AC3EncodeContext *s)
        coordinates in successive blocks */
     for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
         blk = 0;
-        while (blk < AC3_MAX_BLOCKS) {
+        while (blk < s->num_blocks) {
             int blk1;
             CoefSumType energy_cpl;
             AC3Block *block  = &s->blocks[blk];
@@ -273,7 +273,7 @@ static void apply_channel_coupling(AC3EncodeContext *s)
 
             energy_cpl = energy[blk][CPL_CH][bnd];
             blk1 = blk+1;
-            while (!s->blocks[blk1].new_cpl_coords && blk1 < AC3_MAX_BLOCKS) {
+            while (!s->blocks[blk1].new_cpl_coords && blk1 < s->num_blocks) {
                 if (s->blocks[blk1].cpl_in_use)
                     energy_cpl += energy[blk1][CPL_CH][bnd];
                 blk1++;
@@ -285,7 +285,7 @@ static void apply_channel_coupling(AC3EncodeContext *s)
                     continue;
                 energy_ch = energy[blk][ch][bnd];
                 blk1 = blk+1;
-                while (!s->blocks[blk1].new_cpl_coords && blk1 < AC3_MAX_BLOCKS) {
+                while (!s->blocks[blk1].new_cpl_coords && blk1 < s->num_blocks) {
                     if (s->blocks[blk1].cpl_in_use)
                         energy_ch += energy[blk1][ch][bnd];
                     blk1++;
@@ -297,7 +297,7 @@ static void apply_channel_coupling(AC3EncodeContext *s)
     }
 
     /* calculate exponents/mantissas for coupling coordinates */
-    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_coords)
             continue;
@@ -362,7 +362,7 @@ static void compute_rematrixing_strategy(AC3EncodeContext *s)
     if (s->channel_mode != AC3_CHMODE_STEREO)
         return;
 
-    for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
+    for (blk = 0; blk < s->num_blocks; blk++) {
         block = &s->blocks[blk];
         block->new_rematrixing_strategy = !blk;
 
@@ -440,7 +440,7 @@ int AC3_NAME(encode_frame)(AVCodecContext *avctx, unsigned char *frame,
         scale_coefficients(s);
 
     clip_coefficients(&s->dsp, s->blocks[0].mdct_coef[1],
-                      AC3_MAX_COEFS * AC3_MAX_BLOCKS * s->channels);
+                      AC3_MAX_COEFS * s->num_blocks * s->channels);
 
     s->cpl_on = s->cpl_enabled;
     ff_ac3_compute_coupling_strategy(s);

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);
 }