[FFmpeg-cvslog] r26019 - trunk/libavcodec/ac3enc.c
jbr
subversion
Wed Dec 15 18:28:45 CET 2010
Author: jbr
Date: Wed Dec 15 18:28:44 2010
New Revision: 26019
Log:
cosmetics: comment clean-up and misc cosmetics
Modified:
trunk/libavcodec/ac3enc.c
Modified: trunk/libavcodec/ac3enc.c
==============================================================================
--- trunk/libavcodec/ac3enc.c Wed Dec 15 18:28:41 2010 (r26018)
+++ trunk/libavcodec/ac3enc.c Wed Dec 15 18:28:44 2010 (r26019)
@@ -144,7 +144,8 @@ static void adjust_frame_size(AC3EncodeC
s->bits_written -= s->bit_rate;
s->samples_written -= s->sample_rate;
}
- s->frame_size = s->frame_size_min + 2 * (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate);
+ s->frame_size = s->frame_size_min +
+ 2 * (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate);
s->bits_written += s->frame_size * 8;
s->samples_written += AC3_FRAME_SIZE;
}
@@ -401,7 +402,7 @@ static void lshift_tab(int16_t *tab, int
int i;
if (lshift > 0) {
- for(i = 0; i < n; i++)
+ for (i = 0; i < n; i++)
tab[i] <<= lshift;
} else if (lshift < 0) {
lshift = -lshift;
@@ -460,10 +461,8 @@ static void extract_exponents(AC3EncodeC
{
int blk, ch, i;
- /* extract exponents */
for (ch = 0; ch < s->channels; ch++) {
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
- /* compute "exponents". We take into account the normalization there */
AC3Block *block = &s->blocks[blk];
for (i = 0; i < AC3_MAX_COEFS; i++) {
int e;
@@ -576,7 +575,7 @@ static void compute_exp_strategy(AC3Enco
* exponent in the same frequency bin of a following block.
* exp[i] = min(exp[i], exp1[i]
*/
-static void exponent_min(uint8_t exp[AC3_MAX_COEFS], uint8_t exp1[AC3_MAX_COEFS], int n)
+static void exponent_min(uint8_t *exp, uint8_t *exp1, int n)
{
int i;
for (i = 0; i < n; i++) {
@@ -589,8 +588,7 @@ static void exponent_min(uint8_t exp[AC3
/**
* Update the exponents so that they are the ones the decoder will decode.
*/
-static void encode_exponents_blk_ch(uint8_t encoded_exp[AC3_MAX_COEFS],
- uint8_t exp[AC3_MAX_COEFS],
+static void encode_exponents_blk_ch(uint8_t *encoded_exp, uint8_t *exp,
int nb_exps, int exp_strategy,
uint8_t *num_exp_groups)
{
@@ -649,12 +647,12 @@ static void encode_exponents(AC3EncodeCo
AC3Block *block, *block1, *block2;
for (ch = 0; ch < s->channels; ch++) {
- /* for the EXP_REUSE case we select the min of the exponents */
blk = 0;
block = &s->blocks[0];
while (blk < AC3_MAX_BLOCKS) {
blk1 = blk + 1;
block1 = block + 1;
+ /* for the EXP_REUSE case we select the min of the exponents */
while (blk1 < AC3_MAX_BLOCKS && block1->exp_strategy[ch] == EXP_REUSE) {
exponent_min(block->exp[ch], block1->exp[ch], s->nb_coefs[ch]);
blk1++;
@@ -833,26 +831,26 @@ static void count_frame_bits(AC3EncodeCo
/**
* Calculate the number of bits needed to encode a set of mantissas.
*/
-static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *m, int nb_coefs)
+static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *bap, int nb_coefs)
{
- int bits, mant, i;
+ int bits, b, i;
bits = 0;
for (i = 0; i < nb_coefs; i++) {
- mant = m[i];
- switch (mant) {
+ b = bap[i];
+ switch (b) {
case 0:
- /* nothing */
+ /* bap=0 mantissas are not encoded */
break;
case 1:
- /* 3 mantissa in 5 bits */
+ /* 3 mantissas in 5 bits */
if (s->mant1_cnt == 0)
bits += 5;
if (++s->mant1_cnt == 3)
s->mant1_cnt = 0;
break;
case 2:
- /* 3 mantissa in 7 bits */
+ /* 3 mantissas in 7 bits */
if (s->mant2_cnt == 0)
bits += 7;
if (++s->mant2_cnt == 3)
@@ -862,7 +860,7 @@ static int compute_mantissa_size(AC3Enco
bits += 3;
break;
case 4:
- /* 2 mantissa in 7 bits */
+ /* 2 mantissas in 7 bits */
if (s->mant4_cnt == 0)
bits += 7;
if (++s->mant4_cnt == 2)
@@ -875,7 +873,7 @@ static int compute_mantissa_size(AC3Enco
bits += 16;
break;
default:
- bits += mant - 1;
+ bits += b - 1;
break;
}
}
@@ -966,9 +964,8 @@ static int cbr_bit_allocation(AC3EncodeC
bit_alloc(s, s->bap, snr_offset) > bits_left) {
snr_offset -= 64;
}
- if (snr_offset < 0) {
+ if (snr_offset < 0)
return AVERROR(EINVAL);
- }
while (snr_offset + 64 <= 1023 &&
bit_alloc(s, s->bap1, snr_offset + 64) <= bits_left) {
@@ -1007,10 +1004,8 @@ static int cbr_bit_allocation(AC3EncodeC
*/
static int compute_bit_allocation(AC3EncodeContext *s)
{
- /* count frame bits other than exponents and mantissas */
count_frame_bits(s);
- /* calculate psd and masking curve before doing bit allocation */
bit_alloc_masking(s);
return cbr_bit_allocation(s);
@@ -1033,7 +1028,7 @@ static inline int sym_quant(int c, int e
v = (v + 1) >> 1;
v = (levels >> 1) - v;
}
- assert (v >= 0 && v < levels);
+ assert(v >= 0 && v < levels);
return v;
}
@@ -1217,11 +1212,18 @@ static void output_audio_block(AC3Encode
int ch, i, baie, rbnd;
AC3Block *block = &s->blocks[block_num];
+ /* block switching */
for (ch = 0; ch < s->fbw_channels; ch++)
- put_bits(&s->pb, 1, 0); /* no block switching */
+ put_bits(&s->pb, 1, 0);
+
+ /* dither flags */
for (ch = 0; ch < s->fbw_channels; ch++)
- put_bits(&s->pb, 1, 1); /* no dither */
- put_bits(&s->pb, 1, 0); /* no dynamic range */
+ put_bits(&s->pb, 1, 1);
+
+ /* dynamic range codes */
+ put_bits(&s->pb, 1, 0);
+
+ /* channel coupling */
if (!block_num) {
put_bits(&s->pb, 1, 1); /* coupling strategy present */
put_bits(&s->pb, 1, 0); /* no coupling strategy */
@@ -1229,6 +1231,7 @@ static void output_audio_block(AC3Encode
put_bits(&s->pb, 1, 0); /* no new coupling strategy */
}
+ /* stereo rematrixing */
if (s->channel_mode == AC3_CHMODE_STEREO) {
if (!block_num) {
/* first block must define rematrixing (rematstr) */
@@ -1246,7 +1249,6 @@ static void output_audio_block(AC3Encode
/* exponent strategy */
for (ch = 0; ch < s->fbw_channels; ch++)
put_bits(&s->pb, 2, block->exp_strategy[ch]);
-
if (s->lfe_on)
put_bits(&s->pb, 1, block->exp_strategy[s->lfe_channel]);
@@ -1261,15 +1263,16 @@ static void output_audio_block(AC3Encode
if (block->exp_strategy[ch] == EXP_REUSE)
continue;
- /* first exponent */
+ /* DC exponent */
put_bits(&s->pb, 4, block->grouped_exp[ch][0]);
- /* next ones are delta-encoded and grouped */
+ /* exponent groups */
for (i = 1; i <= block->num_exp_groups[ch]; i++)
put_bits(&s->pb, 7, block->grouped_exp[ch][i]);
+ /* gain range info */
if (ch != s->lfe_channel)
- put_bits(&s->pb, 2, 0); /* no gain range info */
+ put_bits(&s->pb, 2, 0);
}
/* bit allocation info */
@@ -1296,10 +1299,9 @@ static void output_audio_block(AC3Encode
put_bits(&s->pb, 1, 0); /* no delta bit allocation */
put_bits(&s->pb, 1, 0); /* no data to skip */
- /* mantissa encoding */
+ /* mantissas */
for (ch = 0; ch < s->channels; ch++) {
int b, q;
-
for (i = 0; i < s->nb_coefs[ch]; i++) {
q = block->qmant[ch][i];
b = s->bap[block_num][ch][i];
@@ -1361,28 +1363,27 @@ static void output_frame_end(AC3EncodeCo
int frame_size, frame_size_58, pad_bytes, crc1, crc2, crc_inv;
uint8_t *frame;
- frame_size = s->frame_size; /* frame size in words */
- /* align to 8 bits */
+ frame_size = s->frame_size;
+ frame_size_58 = ((frame_size >> 2) + (frame_size >> 4)) << 1;
+
+ /* pad the remainder of the frame with zeros */
flush_put_bits(&s->pb);
- /* add zero bytes to reach the frame size */
frame = s->pb.buf;
pad_bytes = s->frame_size - (put_bits_ptr(&s->pb) - frame) - 2;
assert(pad_bytes >= 0);
if (pad_bytes > 0)
memset(put_bits_ptr(&s->pb), 0, pad_bytes);
- /* Now we must compute both crcs : this is not so easy for crc1
- because it is at the beginning of the data... */
- frame_size_58 = ((frame_size >> 2) + (frame_size >> 4)) << 1;
-
+ /* compute crc1 */
+ /* this is not so easy because it is at the beginning of the data... */
crc1 = av_bswap16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
frame + 4, frame_size_58 - 4));
-
/* XXX: could precompute crc_inv */
crc_inv = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY);
crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
AV_WB16(frame + 2, crc1);
+ /* compute crc2 */
crc2 = av_bswap16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
frame + frame_size_58,
frame_size - frame_size_58 - 2));
@@ -1402,9 +1403,8 @@ static void output_frame(AC3EncodeContex
output_frame_header(s);
- for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
+ for (blk = 0; blk < AC3_MAX_BLOCKS; blk++)
output_audio_block(s, blk);
- }
output_frame_end(s);
}
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