They introduce too much complexity for very little benefit. The result is that
encoding will be more likely to fail at extremely low bitrates where quality
would be awful anyway.
---
libavcodec/ac3enc.c | 71 +--------------------------------------------------
1 files changed, 1 insertions(+), 70 deletions(-)
diff --git a/libavcodec/ac3enc.c b/libavcodec/ac3enc.c
index 1f7d05e..3fbbbd0 100644
--- a/libavcodec/ac3enc.c
+++ b/libavcodec/ac3enc.c
@@ -1023,47 +1023,6 @@ static int cbr_bit_allocation(AC3EncodeContext *s)
/**
- * Downgrade exponent strategies to reduce the bits used by the exponents.
- * This is a fallback for when bit allocation fails with the normal exponent
- * strategies. Each time this function is run it only downgrades the
- * strategy in 1 channel of 1 block.
- * @return non-zero if downgrade was unsuccessful
- */
-static int downgrade_exponents(AC3EncodeContext *s)
-{
- int ch, blk;
-
- for (blk = AC3_MAX_BLOCKS-1; blk >= 0; blk--) {
- for (ch = !s->blocks[blk].cpl_in_use; ch <= s->fbw_channels; ch++) {
- if (s->exp_strategy[ch][blk] == EXP_D15) {
- s->exp_strategy[ch][blk] = EXP_D25;
- return 0;
- }
- }
- }
- for (blk = AC3_MAX_BLOCKS-1; blk >= 0; blk--) {
- for (ch = !s->blocks[blk].cpl_in_use; ch <= s->fbw_channels; ch++) {
- if (s->exp_strategy[ch][blk] == EXP_D25) {
- s->exp_strategy[ch][blk] = EXP_D45;
- return 0;
- }
- }
- }
- /* block 0 cannot reuse exponents, so only downgrade D45 to REUSE if
- the block number > 0 */
- for (blk = AC3_MAX_BLOCKS-1; blk > 0; blk--) {
- for (ch = !s->blocks[blk].cpl_in_use; ch <= s->fbw_channels; ch++) {
- if (s->exp_strategy[ch][blk] > EXP_REUSE) {
- s->exp_strategy[ch][blk] = EXP_REUSE;
- return 0;
- }
- }
- }
- return -1;
-}
-
-
-/**
* Perform bit allocation search.
* Finds the SNR offset value that maximizes quality and fits in the specified
* frame size. Output is the SNR offset and a set of bit allocation pointers
@@ -1071,39 +1030,11 @@ static int downgrade_exponents(AC3EncodeContext *s)
*/
static int compute_bit_allocation(AC3EncodeContext *s)
{
- int ret;
-
count_frame_bits(s);
bit_alloc_masking(s);
- ret = cbr_bit_allocation(s);
- while (ret) {
- /* fallback 1: disable channel coupling */
- if (s->cpl_on) {
- s->cpl_on = 0;
- compute_coupling_strategy(s);
- s->compute_rematrixing_strategy(s);
- apply_rematrixing(s);
- process_exponents(s);
- ret = compute_bit_allocation(s);
- continue;
- }
-
- /* fallback 2: downgrade exponents */
- if (!downgrade_exponents(s)) {
- extract_exponents(s);
- encode_exponents(s);
- group_exponents(s);
- ret = compute_bit_allocation(s);
- continue;
- }
-
- /* fallbacks were not enough... */
- break;
- }
-
- return ret;
+ return cbr_bit_allocation(s);
}
--
1.7.1
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