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Deinterleave whole frame at once instead of per-block. 

This reduces the amount of memcpy() by using pointers to overlap samples for
successive blocks rather than copying.

Originally committed as revision 25986 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles 2010-12-14 14:52:46 +00:00
parent e0685bc98f
commit 12ed622699
1 changed files with 26 additions and 16 deletions
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42
libavcodec/ac3enc.c
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@ -1082,6 +1082,7 @@ static int ac3_encode_frame(AVCodecContext *avctx,
const int16_t *samples = data;
int v;
int blk, blk1, blk2, ch, i;
int16_t planar_samples[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE+AC3_FRAME_SIZE];
int16_t input_samples[AC3_WINDOW_SIZE];
int32_t mdct_coef[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
@ -1091,30 +1092,39 @@ static int ac3_encode_frame(AVCodecContext *avctx,
int8_t exp_shift[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS];
int frame_bits;
/* deinterleave and remap input samples */
for (ch = 0; ch < s->channels; ch++) {
const int16_t *sptr;
int sinc;
/* copy last 256 samples of previous frame to the start of the current frame */
memcpy(&planar_samples[ch][0], s->last_samples[ch],
AC3_BLOCK_SIZE * sizeof(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++) {
planar_samples[ch][i] = *sptr;
sptr += sinc;
}
/* save last 256 samples for next frame */
memcpy(s->last_samples[ch], &planar_samples[ch][6* AC3_BLOCK_SIZE],
AC3_BLOCK_SIZE * sizeof(planar_samples[0][0]));
}
frame_bits = 0;
for (ch = 0; ch < s->channels; ch++) {
int ich = s->channel_map[ch];
/* fixed mdct to the six sub blocks & exponent computation */
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
const int16_t *sptr;
int sinc;
/* compute input samples */
memcpy(input_samples, s->last_samples[ich], AC3_BLOCK_SIZE * sizeof(int16_t));
sinc = s->channels;
sptr = samples + (sinc * AC3_BLOCK_SIZE * blk) + ich;
for (i = 0; i < AC3_BLOCK_SIZE; i++) {
v = *sptr;
input_samples[i + AC3_BLOCK_SIZE] = v;
s->last_samples[ich][i] = v;
sptr += sinc;
}
int16_t *src_samples = &planar_samples[ch][blk * AC3_BLOCK_SIZE];
/* apply the MDCT window */
for (i = 0; i < AC3_BLOCK_SIZE; i++) {
input_samples[i] = MUL16(input_samples[i],
input_samples[i] = MUL16(src_samples[i],
ff_ac3_window[i]) >> 15;
input_samples[AC3_WINDOW_SIZE-i-1] = MUL16(input_samples[AC3_WINDOW_SIZE-i-1],
input_samples[AC3_WINDOW_SIZE-i-1] = MUL16(src_samples[AC3_WINDOW_SIZE-i-1],
ff_ac3_window[i]) >> 15;
}