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Redesign encode_exponents_blk_ch() so that duplicate exponent sets are no 

longer required. This gets rid of the temp buffer as well as encoded_exp in
AC3EncodeContext. It also allows for skipping the exponent grouping for
EXP_D15. 56% faster in encode_exponents_blk_ch().

Originally committed as revision 26034 to svn://svn.ffmpeg.org/ffmpeg/trunk
tags/n0.8
Justin Ruggles 15 years ago
parent
8846ee54ad
commit
27af78cf0e
1 changed files with 23 additions and 30 deletions
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  1. +23
    -30
      libavcodec/ac3enc.c

+ 23
- 30
libavcodec/ac3enc.c View File

@@ -1,6 +1,8 @@
/*
* The simplest AC-3 encoder
* Copyright (c) 2000 Fabrice Bellard
* Copyright (c) 2006-2010 Justin Ruggles <justin.ruggles@gmail.com>
* Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de>
*
* This file is part of FFmpeg.
*
@@ -69,7 +71,6 @@ typedef struct AC3Block {
uint8_t **bap; ///< bit allocation pointers (bap)
int32_t **mdct_coef; ///< MDCT coefficients
uint8_t **exp; ///< original exponents
uint8_t **encoded_exp; ///< encoded exponents
uint8_t **grouped_exp; ///< grouped exponents
int16_t **psd; ///< psd per frequency bin
int16_t **band_psd; ///< psd per critical band
@@ -134,7 +135,6 @@ typedef struct AC3EncodeContext {
uint8_t *bap1_buffer;
int32_t *mdct_coef_buffer;
uint8_t *exp_buffer;
uint8_t *encoded_exp_buffer;
uint8_t *grouped_exp_buffer;
int16_t *psd_buffer;
int16_t *band_psd_buffer;
@@ -606,19 +606,18 @@ static void exponent_min(uint8_t *exp, uint8_t *exp1, int n)
/**
* Update the exponents so that they are the ones the decoder will decode.
*/
static void encode_exponents_blk_ch(uint8_t *encoded_exp, uint8_t *exp,
static void encode_exponents_blk_ch(uint8_t *exp,
int nb_exps, int exp_strategy,
uint8_t *num_exp_groups)
{
int group_size, nb_groups, i, j, k, exp_min;
uint8_t exp1[AC3_MAX_COEFS];

group_size = exp_strategy + (exp_strategy == EXP_D45);
*num_exp_groups = (nb_exps + (group_size * 3) - 4) / (3 * group_size);
nb_groups = *num_exp_groups * 3;

/* for each group, compute the minimum exponent */
exp1[0] = exp[0]; /* DC exponent is handled separately */
if (exp_strategy > EXP_D15) {
k = 1;
for (i = 1; i <= nb_groups; i++) {
exp_min = exp[k];
@@ -627,28 +626,30 @@ static void encode_exponents_blk_ch(uint8_t *encoded_exp, uint8_t *exp,
if (exp[k+j] < exp_min)
exp_min = exp[k+j];
}
exp1[i] = exp_min;
exp[i] = exp_min;
k += group_size;
}
}

/* constraint for DC exponent */
if (exp1[0] > 15)
exp1[0] = 15;
if (exp[0] > 15)
exp[0] = 15;

/* decrease the delta between each groups to within 2 so that they can be
differentially encoded */
for (i = 1; i <= nb_groups; i++)
exp1[i] = FFMIN(exp1[i], exp1[i-1] + 2);
exp[i] = FFMIN(exp[i], exp[i-1] + 2);
for (i = nb_groups-1; i >= 0; i--)
exp1[i] = FFMIN(exp1[i], exp1[i+1] + 2);
exp[i] = FFMIN(exp[i], exp[i+1] + 2);

/* now we have the exponent values the decoder will see */
encoded_exp[0] = exp1[0];
k = 1;
for (i = 1; i <= nb_groups; i++) {
if (exp_strategy > EXP_D15) {
k = nb_groups * group_size;
for (i = nb_groups; i > 0; i--) {
for (j = 0; j < group_size; j++)
encoded_exp[k+j] = exp1[i];
k += group_size;
exp[k-j] = exp[i];
k -= group_size;
}
}
}

@@ -676,14 +677,13 @@ static void encode_exponents(AC3EncodeContext *s)
blk1++;
block1++;
}
encode_exponents_blk_ch(block->encoded_exp[ch],
block->exp[ch], s->nb_coefs[ch],
encode_exponents_blk_ch(block->exp[ch], s->nb_coefs[ch],
block->exp_strategy[ch],
&block->num_exp_groups[ch]);
/* copy encoded exponents for reuse case */
block2 = block + 1;
for (blk2 = blk+1; blk2 < blk1; blk2++, block2++) {
memcpy(block2->encoded_exp[ch], block->encoded_exp[ch],
memcpy(block2->exp[ch], block->exp[ch],
s->nb_coefs[ch] * sizeof(uint8_t));
}
blk = blk1;
@@ -716,7 +716,7 @@ static void group_exponents(AC3EncodeContext *s)
}
group_size = block->exp_strategy[ch] + (block->exp_strategy[ch] == EXP_D45);
bit_count += 4 + (block->num_exp_groups[ch] * 7);
p = block->encoded_exp[ch];
p = block->exp[ch];

/* DC exponent */
exp1 = *p++;
@@ -915,7 +915,7 @@ static void bit_alloc_masking(AC3EncodeContext *s)
memcpy(block->psd[ch], block1->psd[ch], AC3_MAX_COEFS*sizeof(block->psd[0][0]));
memcpy(block->mask[ch], block1->mask[ch], AC3_CRITICAL_BANDS*sizeof(block->mask[0][0]));
} else {
ff_ac3_bit_alloc_calc_psd(block->encoded_exp[ch], 0,
ff_ac3_bit_alloc_calc_psd(block->exp[ch], 0,
s->nb_coefs[ch],
block->psd[ch], block->band_psd[ch]);
ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, block->band_psd[ch],
@@ -1098,7 +1098,7 @@ static inline int asym_quant(int c, int e, int qbits)
*/
static void quantize_mantissas_blk_ch(AC3EncodeContext *s,
int32_t *mdct_coef, int8_t exp_shift,
uint8_t *encoded_exp, uint8_t *bap,
uint8_t *exp, uint8_t *bap,
uint16_t *qmant, int n)
{
int i;
@@ -1106,7 +1106,7 @@ static void quantize_mantissas_blk_ch(AC3EncodeContext *s,
for (i = 0; i < n; i++) {
int v;
int c = mdct_coef[i];
int e = encoded_exp[i] - exp_shift;
int e = exp[i] - exp_shift;
int b = bap[i];
switch (b) {
case 0:
@@ -1203,7 +1203,7 @@ static void quantize_mantissas(AC3EncodeContext *s)

for (ch = 0; ch < s->channels; ch++) {
quantize_mantissas_blk_ch(s, block->mdct_coef[ch], block->exp_shift[ch],
block->encoded_exp[ch], block->bap[ch],
block->exp[ch], block->bap[ch],
block->qmant[ch], s->nb_coefs[ch]);
}
}
@@ -1496,7 +1496,6 @@ static av_cold int ac3_encode_close(AVCodecContext *avctx)
av_freep(&s->bap1_buffer);
av_freep(&s->mdct_coef_buffer);
av_freep(&s->exp_buffer);
av_freep(&s->encoded_exp_buffer);
av_freep(&s->grouped_exp_buffer);
av_freep(&s->psd_buffer);
av_freep(&s->band_psd_buffer);
@@ -1507,7 +1506,6 @@ static av_cold int ac3_encode_close(AVCodecContext *avctx)
av_freep(&block->bap);
av_freep(&block->mdct_coef);
av_freep(&block->exp);
av_freep(&block->encoded_exp);
av_freep(&block->grouped_exp);
av_freep(&block->psd);
av_freep(&block->band_psd);
@@ -1667,8 +1665,6 @@ static av_cold int allocate_buffers(AVCodecContext *avctx)
AC3_MAX_COEFS * sizeof(*s->mdct_coef_buffer), alloc_fail);
FF_ALLOC_OR_GOTO(avctx, s->exp_buffer, AC3_MAX_BLOCKS * s->channels *
AC3_MAX_COEFS * sizeof(*s->exp_buffer), alloc_fail);
FF_ALLOC_OR_GOTO(avctx, s->encoded_exp_buffer, AC3_MAX_BLOCKS * s->channels *
AC3_MAX_COEFS * sizeof(*s->encoded_exp_buffer), alloc_fail);
FF_ALLOC_OR_GOTO(avctx, s->grouped_exp_buffer, AC3_MAX_BLOCKS * s->channels *
128 * sizeof(*s->grouped_exp_buffer), alloc_fail);
FF_ALLOC_OR_GOTO(avctx, s->psd_buffer, AC3_MAX_BLOCKS * s->channels *
@@ -1687,8 +1683,6 @@ static av_cold int allocate_buffers(AVCodecContext *avctx)
alloc_fail);
FF_ALLOCZ_OR_GOTO(avctx, block->exp, s->channels * sizeof(*block->exp),
alloc_fail);
FF_ALLOCZ_OR_GOTO(avctx, block->encoded_exp, s->channels * sizeof(*block->encoded_exp),
alloc_fail);
FF_ALLOCZ_OR_GOTO(avctx, block->grouped_exp, s->channels * sizeof(*block->grouped_exp),
alloc_fail);
FF_ALLOCZ_OR_GOTO(avctx, block->psd, s->channels * sizeof(*block->psd),
@@ -1704,7 +1698,6 @@ static av_cold int allocate_buffers(AVCodecContext *avctx)
block->bap[ch] = &s->bap_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
block->mdct_coef[ch] = &s->mdct_coef_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
block->exp[ch] = &s->exp_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
block->encoded_exp[ch] = &s->encoded_exp_buffer[AC3_MAX_COEFS * (blk * s->channels + ch)];
block->grouped_exp[ch] = &s->grouped_exp_buffer[128 * (blk * s->channels + ch)];
block->psd[ch] = &s->psd_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
block->band_psd[ch] = &s->band_psd_buffer [64 * (blk * s->channels + ch)];


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