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flacdec: Simplify frame sync by not using the bitstream reader. 

Originally committed as revision 17818 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles 2009-03-05 01:15:38 +00:00
parent a8ec12bc2e
commit fd6fd470ce
1 changed files with 11 additions and 9 deletions
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20
libavcodec/flacdec.c
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@ -610,7 +610,7 @@ static int flac_decode_frame(AVCodecContext *avctx,
const uint8_t *buf, int buf_size) const uint8_t *buf, int buf_size)
{ {
FLACContext *s = avctx->priv_data; FLACContext *s = avctx->priv_data;
int tmp = 0, i, j = 0, input_buf_size = 0, bytes_read = 0; int i, j = 0, input_buf_size = 0, bytes_read = 0;
int16_t *samples_16 = data; int16_t *samples_16 = data;
int32_t *samples_32 = data; int32_t *samples_32 = data;
int alloc_data_size= *data_size; int alloc_data_size= *data_size;
@ -664,15 +664,18 @@ static int flac_decode_frame(AVCodecContext *avctx,
goto end; goto end;
} }
init_get_bits(&s->gb, buf, buf_size*8); /* check for frame sync code and resync stream if necessary */
if ((AV_RB16(buf) & 0xFFFE) != 0xFFF8) {
tmp = show_bits(&s->gb, 16); const uint8_t *buf_end = buf + buf_size;
if ((tmp & 0xFFFE) != 0xFFF8) {
av_log(s->avctx, AV_LOG_ERROR, "FRAME HEADER not here\n"); av_log(s->avctx, AV_LOG_ERROR, "FRAME HEADER not here\n");
while (get_bits_count(&s->gb)/8+2 < buf_size && (show_bits(&s->gb, 16) & 0xFFFE) != 0xFFF8) while (buf+2 < buf_end && (AV_RB16(buf) & 0xFFFE) != 0xFFF8)
skip_bits(&s->gb, 8); buf++;
goto hdr_end; // we may not have enough bits left to decode a frame, so try next time bytes_read = buf_size - (buf_end - buf);
goto end; // we may not have enough bits left to decode a frame, so try next time
} }
/* decode frame */
init_get_bits(&s->gb, buf, buf_size*8);
skip_bits(&s->gb, 16); skip_bits(&s->gb, 16);
if (decode_frame(s, alloc_data_size) < 0) { if (decode_frame(s, alloc_data_size) < 0) {
av_log(s->avctx, AV_LOG_ERROR, "decode_frame() failed\n"); av_log(s->avctx, AV_LOG_ERROR, "decode_frame() failed\n");
@ -717,7 +720,6 @@ static int flac_decode_frame(AVCodecContext *avctx,
*data_size = s->blocksize * s->channels * (s->is32 ? 4 : 2); *data_size = s->blocksize * s->channels * (s->is32 ? 4 : 2);
hdr_end:
bytes_read = (get_bits_count(&s->gb)+7)/8; bytes_read = (get_bits_count(&s->gb)+7)/8;
end: end:
if (bytes_read > buf_size) { if (bytes_read > buf_size) {