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Split out grouping of exponents into a separate function. 

Originally committed as revision 25998 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles 2010-12-14 14:53:26 +00:00
parent b6a1e5236e
commit f94bacc538
1 changed files with 93 additions and 52 deletions
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145
libavcodec/ac3enc.c
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@ -37,6 +37,9 @@
#define MDCT_NBITS 9
#define MDCT_SAMPLES (1 << MDCT_NBITS)
/** Maximum number of exponent groups. +1 for separate DC exponent. */
#define AC3_MAX_EXP_GROUPS 85
/** Scale a float value by 2^bits and convert to an integer. */
#define SCALE_FLOAT(a, bits) lrintf((a) * (float)(1 << (bits)))
@ -569,11 +572,10 @@ static void exponent_min(uint8_t exp[AC3_MAX_COEFS], uint8_t exp1[AC3_MAX_COEFS]
/**
* Update the exponents so that they are the ones the decoder will decode.
* @return the number of bits used to encode the exponents.
*/
static int encode_exponents_blk_ch(uint8_t encoded_exp[AC3_MAX_COEFS],
uint8_t exp[AC3_MAX_COEFS],
int nb_exps, int exp_strategy)
static void encode_exponents_blk_ch(uint8_t encoded_exp[AC3_MAX_COEFS],
uint8_t exp[AC3_MAX_COEFS],
int nb_exps, int exp_strategy)
{
int group_size, nb_groups, i, j, k, exp_min;
uint8_t exp1[AC3_MAX_COEFS];
@ -614,8 +616,6 @@ static int encode_exponents_blk_ch(uint8_t encoded_exp[AC3_MAX_COEFS],
encoded_exp[k+j] = exp1[i];
k += group_size;
}
return 4 + (nb_groups / 3) * 7;
}
@ -624,17 +624,14 @@ static int encode_exponents_blk_ch(uint8_t encoded_exp[AC3_MAX_COEFS],
* This copies and groups exponents based on exponent strategy and reduces
* deltas between adjacent exponent groups so that they can be differentially
* encoded.
* @return bits needed to encode the exponents
*/
static int encode_exponents(AC3EncodeContext *s,
uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS])
static void encode_exponents(AC3EncodeContext *s,
uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS])
{
int blk, blk1, blk2, ch;
int frame_bits;
frame_bits = 0;
for (ch = 0; ch < s->channels; ch++) {
/* for the EXP_REUSE case we select the min of the exponents */
blk = 0;
@ -644,7 +641,7 @@ static int encode_exponents(AC3EncodeContext *s,
exponent_min(exp[blk][ch], exp[blk1][ch], s->nb_coefs[ch]);
blk1++;
}
frame_bits += encode_exponents_blk_ch(encoded_exp[blk][ch],
encode_exponents_blk_ch(encoded_exp[blk][ch],
exp[blk][ch], s->nb_coefs[ch],
exp_strategy[blk][ch]);
/* copy encoded exponents for reuse case */
@ -655,8 +652,67 @@ static int encode_exponents(AC3EncodeContext *s,
blk = blk1;
}
}
}
return frame_bits;
/**
* Group exponents.
* 3 delta-encoded exponents are in each 7-bit group. The number of groups
* varies depending on exponent strategy and bandwidth.
* @return bits needed to encode the exponents
*/
static int group_exponents(AC3EncodeContext *s,
uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
uint8_t num_exp_groups[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
uint8_t grouped_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_EXP_GROUPS])
{
int blk, ch, i;
int group_size, bit_count;
uint8_t *p;
int delta0, delta1, delta2;
int exp0, exp1;
bit_count = 0;
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
for (ch = 0; ch < s->channels; ch++) {
if (exp_strategy[blk][ch] == EXP_REUSE) {
num_exp_groups[blk][ch] = 0;
continue;
}
group_size = exp_strategy[blk][ch] + (exp_strategy[blk][ch] == EXP_D45);
num_exp_groups[blk][ch] = (s->nb_coefs[ch] + (group_size * 3) - 4) / (3 * group_size);
bit_count += 4 + (num_exp_groups[blk][ch] * 7);
p = encoded_exp[blk][ch];
/* DC exponent */
exp1 = *p++;
grouped_exp[blk][ch][0] = exp1;
/* remaining exponents are delta encoded */
for (i = 1; i <= num_exp_groups[blk][ch]; i++) {
/* merge three delta in one code */
exp0 = exp1;
exp1 = p[0];
p += group_size;
delta0 = exp1 - exp0 + 2;
exp0 = exp1;
exp1 = p[0];
p += group_size;
delta1 = exp1 - exp0 + 2;
exp0 = exp1;
exp1 = p[0];
p += group_size;
delta2 = exp1 - exp0 + 2;
grouped_exp[blk][ch][i] = ((delta0 * 5 + delta1) * 5) + delta2;
}
}
}
return bit_count;
}
@ -671,13 +727,17 @@ static int process_exponents(AC3EncodeContext *s,
int8_t exp_shift[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS])
uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
uint8_t num_exp_groups[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
uint8_t grouped_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_EXP_GROUPS])
{
extract_exponents(s, mdct_coef, exp_shift, exp);
compute_exp_strategy(s, exp_strategy, exp);
return encode_exponents(s, exp, exp_strategy, encoded_exp);
encode_exponents(s, exp, exp_strategy, encoded_exp);
return group_exponents(s, encoded_exp, exp_strategy, num_exp_groups, grouped_exp);
}
@ -1125,15 +1185,13 @@ static void output_frame_header(AC3EncodeContext *s)
*/
static void output_audio_block(AC3EncodeContext *s,
uint8_t exp_strategy[AC3_MAX_CHANNELS],
uint8_t encoded_exp[AC3_MAX_CHANNELS][AC3_MAX_COEFS],
uint8_t num_exp_groups[AC3_MAX_CHANNELS],
uint8_t grouped_exp[AC3_MAX_CHANNELS][AC3_MAX_EXP_GROUPS],
uint8_t bap[AC3_MAX_CHANNELS][AC3_MAX_COEFS],
uint16_t qmant[AC3_MAX_CHANNELS][AC3_MAX_COEFS],
int block_num)
{
int ch, nb_groups, group_size, i, baie, rbnd;
uint8_t *p;
int exp0, exp1;
int delta0, delta1, delta2;
int ch, i, baie, rbnd;
for (ch = 0; ch < s->fbw_channels; ch++)
put_bits(&s->pb, 1, 0); /* no block switching */
@ -1178,34 +1236,13 @@ static void output_audio_block(AC3EncodeContext *s,
for (ch = 0; ch < s->channels; ch++) {
if (exp_strategy[ch] == EXP_REUSE)
continue;
group_size = exp_strategy[ch] + (exp_strategy[ch] == EXP_D45);
nb_groups = (s->nb_coefs[ch] + (group_size * 3) - 4) / (3 * group_size);
p = encoded_exp[ch];
/* first exponent */
exp1 = *p++;
put_bits(&s->pb, 4, exp1);
put_bits(&s->pb, 4, grouped_exp[ch][0]);
/* next ones are delta encoded */
for (i = 0; i < nb_groups; i++) {
/* merge three delta in one code */
exp0 = exp1;
exp1 = p[0];
p += group_size;
delta0 = exp1 - exp0 + 2;
exp0 = exp1;
exp1 = p[0];
p += group_size;
delta1 = exp1 - exp0 + 2;
exp0 = exp1;
exp1 = p[0];
p += group_size;
delta2 = exp1 - exp0 + 2;
put_bits(&s->pb, 7, ((delta0 * 5 + delta1) * 5) + delta2);
}
/* next ones are delta-encoded and grouped */
for (i = 1; i <= num_exp_groups[ch]; i++)
put_bits(&s->pb, 7, grouped_exp[ch][i]);
if (ch != s->lfe_channel)
put_bits(&s->pb, 2, 0); /* no gain range info */
@ -1335,7 +1372,8 @@ static void output_frame_end(AC3EncodeContext *s)
static void output_frame(AC3EncodeContext *s,
unsigned char *frame,
uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
uint8_t num_exp_groups[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
uint8_t grouped_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_EXP_GROUPS],
uint8_t bap[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
uint16_t qmant[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS])
{
@ -1346,8 +1384,8 @@ static void output_frame(AC3EncodeContext *s,
output_frame_header(s);
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
output_audio_block(s, exp_strategy[blk], encoded_exp[blk],
bap[blk], qmant[blk], blk);
output_audio_block(s, exp_strategy[blk], num_exp_groups[blk],
grouped_exp[blk], bap[blk], qmant[blk], blk);
}
output_frame_end(s);
@ -1367,6 +1405,8 @@ static int ac3_encode_frame(AVCodecContext *avctx,
uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS];
uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
uint8_t num_exp_groups[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS];
uint8_t grouped_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_EXP_GROUPS];
uint8_t bap[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
int8_t exp_shift[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS];
uint16_t qmant[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
@ -1379,13 +1419,14 @@ static int ac3_encode_frame(AVCodecContext *avctx,
apply_mdct(s, planar_samples, exp_shift, mdct_coef);
frame_bits = process_exponents(s, mdct_coef, exp_shift, exp, exp_strategy, encoded_exp);
frame_bits = process_exponents(s, mdct_coef, exp_shift, exp, exp_strategy,
encoded_exp, num_exp_groups, grouped_exp);
compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits);
quantize_mantissas(s, mdct_coef, exp_shift, encoded_exp, bap, qmant);
output_frame(s, frame, exp_strategy, encoded_exp, bap, qmant);
output_frame(s, frame, exp_strategy, num_exp_groups, grouped_exp, bap, qmant);
return s->frame_size;
}