Initialize the bitbuffer with the correct size of bits that would be
read instead of relying the bitstream reader overreading the correct
values.
---
libavcodec/mpegaudiodec_template.c | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)
diff --git a/libavcodec/mpegaudiodec_template.c
b/libavcodec/mpegaudiodec_template.c
index 820a7ae..12a288f 100644
--- a/libavcodec/mpegaudiodec_template.c
+++ b/libavcodec/mpegaudiodec_template.c
@@ -70,6 +70,7 @@ typedef struct MPADecodeContext {
MPA_DECODE_HEADER
uint8_t last_buf[LAST_BUF_SIZE];
int last_buf_size;
+ int extrasize;
/* next header (used in free format parsing) */
uint32_t free_format_next_header;
GetBitContext gb;
@@ -798,9 +799,10 @@ static void exponents_from_scale_factors(MPADecodeContext
*s, GranuleDef *g,
static void switch_buffer(MPADecodeContext *s, int *pos, int *end_pos,
int *end_pos2)
{
- if (s->in_gb.buffer && *pos >= s->gb.size_in_bits) {
+ if (s->in_gb.buffer && *pos >= s->gb.size_in_bits - s->extrasize) {
s->gb = s->in_gb;
s->in_gb.buffer = NULL;
+ s->extrasize = 0;
assert((get_bits_count(&s->gb) & 7) == 0);
skip_bits_long(&s->gb, *pos - *end_pos);
*end_pos2 =
@@ -1354,19 +1356,16 @@ 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,
+ s->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 */
ff_dlog(s->avctx, "seekback:%d, lastbuf:%d\n",
main_data_begin, s->last_buf_size);
- memcpy(s->last_buf + s->last_buf_size, ptr, extrasize);
+ memcpy(s->last_buf + s->last_buf_size, ptr, s->extrasize);
s->in_gb = s->gb;
- init_get_bits(&s->gb, s->last_buf, s->last_buf_size*8);
-#if !UNCHECKED_BITSTREAM_READER
- s->gb.size_in_bits_plus8 += extrasize * 8;
-#endif
+ init_get_bits(&s->gb, s->last_buf, (s->last_buf_size + s->extrasize) *
8);
s->last_buf_size <<= 3;
for (gr = 0; gr < nb_granules && (s->last_buf_size >> 3) <
main_data_begin; gr++) {
for (ch = 0; ch < s->nb_channels; ch++) {
@@ -1377,10 +1376,11 @@ static int mp_decode_layer3(MPADecodeContext *s)
}
}
skip = s->last_buf_size - 8 * main_data_begin;
- if (skip >= s->gb.size_in_bits && s->in_gb.buffer) {
- skip_bits_long(&s->in_gb, skip - s->gb.size_in_bits);
+ if (skip >= s->gb.size_in_bits - s->extrasize && s->in_gb.buffer) {
+ skip_bits_long(&s->in_gb, skip - s->gb.size_in_bits +
s->extrasize);
s->gb = s->in_gb;
s->in_gb.buffer = NULL;
+ s->extrasize = 0;
} else {
skip_bits_long(&s->gb, skip);
}
@@ -1553,7 +1553,7 @@ static int mp_decode_frame(MPADecodeContext *s, OUT_INT
**samples,
s->last_buf_size=0;
if (s->in_gb.buffer) {
align_get_bits(&s->gb);
- i = get_bits_left(&s->gb)>>3;
+ i = (get_bits_left(&s->gb) >> 3) - s->extrasize;
if (i >= 0 && i <= BACKSTEP_SIZE) {
memmove(s->last_buf, s->gb.buffer +
(get_bits_count(&s->gb)>>3), i);
s->last_buf_size=i;
@@ -1561,12 +1561,12 @@ static int mp_decode_frame(MPADecodeContext *s, OUT_INT
**samples,
av_log(s->avctx, AV_LOG_ERROR, "invalid old backstep %d\n", i);
s->gb = s->in_gb;
s->in_gb.buffer = NULL;
+ s->extrasize = 0;
}
align_get_bits(&s->gb);
assert((get_bits_count(&s->gb) & 7) == 0);
- i = get_bits_left(&s->gb) >> 3;
-
+ i = (get_bits_left(&s->gb) >> 3) - s->extrasize;
if (i < 0 || i > BACKSTEP_SIZE || nb_frames < 0) {
if (i < 0)
av_log(s->avctx, AV_LOG_ERROR, "invalid new backstep %d\n", i);
--
2.6.1
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