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mpegaudiodec: Prevent premature clipping of mp3 input buffer.

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Instead of clipping extrasize based on EXTRABYTES, clip based on the
amount of buffer actually left. Without this fix, there are warbles
and other distortions in the test case below.

http://kevincennis.com/mix/assets/sounds/1901_voxfx.mp3
(cherry picked from commit b716542691)

Signed-off-by: Alex Converse <alex.converse@gmail.com>
This commit is contained in:
Dale Curtis 2012-02-24 13:17:39 -05:00 • committed by Alex Converse
parent d0e53ecff7
commit feed0c6b6a
1 changed files with 4 additions and 2 deletions
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6
libavcodec/mpegaudiodec.c
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@ -40,6 +40,7 @@
#define BACKSTEP_SIZE 512
#define EXTRABYTES 24
#define LAST_BUF_SIZE 2 * BACKSTEP_SIZE + EXTRABYTES
/* layer 3 "granule" */
typedef struct GranuleDef {
@ -63,7 +64,7 @@ typedef struct GranuleDef {
typedef struct MPADecodeContext {
MPA_DECODE_HEADER
uint8_t last_buf[2 * BACKSTEP_SIZE + EXTRABYTES];
uint8_t last_buf[LAST_BUF_SIZE];
int last_buf_size;
/* next header (used in free format parsing) */
uint32_t free_format_next_header;
@ -1378,7 +1379,8 @@ static int mp_decode_layer3(MPADecodeContext *s)
if (!s->adu_mode) {
int skip;
const uint8_t *ptr = s->gb.buffer + (get_bits_count(&s->gb)>>3);
int extrasize = av_clip(get_bits_left(&s->gb) >> 3, 0, EXTRABYTES);
int extrasize = av_clip(get_bits_left(&s->gb) >> 3, 0,
FFMAX(0, LAST_BUF_SIZE - s->last_buf_size));
assert((get_bits_count(&s->gb) & 7) == 0);
/* now we get bits from the main_data_begin offset */
av_dlog(s->avctx, "seekback: %d\n", main_data_begin);