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avcodec/dca_parser: Extend DTS core sync word and fix existing check 

Check extended sync word for 16-bit LE and BE core streams to reduce
probability of alias sync detection. Previously sync word extension was
checked only for 14-bit streams (and this check did not properly work
across buffer boundary).

Use 64-bit parser state to make extended sync word detection work across
buffer boundary.

This is sufficient to make the sample in ticket #4492 parse
successfully.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This commit is contained in:
foo86 2015-04-29 14:14:55 +03:00 committed by Michael Niedermayer
parent 50e46b7f0d
commit e80b2b9c81
1 changed files with 25 additions and 17 deletions
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42
libavcodec/dca_parser.c
View File

@ -32,13 +32,20 @@ typedef struct DCAParseContext {
uint32_t lastmarker;
int size;
int framesize;
int hd_pos;
} DCAParseContext;
#define IS_MARKER(state, i, buf, buf_size) \
((state == DCA_SYNCWORD_CORE_14B_LE && (i < buf_size - 2) && (buf[i + 1] & 0xF0) == 0xF0 && buf[i + 2] == 0x07) || \
(state == DCA_SYNCWORD_CORE_14B_BE && (i < buf_size - 2) && buf[i + 1] == 0x07 && (buf[i + 2] & 0xF0) == 0xF0) || \
state == DCA_SYNCWORD_CORE_LE || state == DCA_SYNCWORD_CORE_BE || state == DCA_SYNCWORD_SUBSTREAM)
#define IS_CORE_MARKER(state) \
(((state & 0xFFFFFFFFF0FF) == (((uint64_t)DCA_SYNCWORD_CORE_14B_LE << 16) | 0xF007)) || \
((state & 0xFFFFFFFFFFF0) == (((uint64_t)DCA_SYNCWORD_CORE_14B_BE << 16) | 0x07F0)) || \
((state & 0xFFFFFFFF00FC) == (((uint64_t)DCA_SYNCWORD_CORE_LE << 16) | 0x00FC)) || \
((state & 0xFFFFFFFFFC00) == (((uint64_t)DCA_SYNCWORD_CORE_BE << 16) | 0xFC00)))
#define IS_EXSS_MARKER(state) ((state & 0xFFFFFFFF) == DCA_SYNCWORD_SUBSTREAM)
#define IS_MARKER(state) (IS_CORE_MARKER(state) || IS_EXSS_MARKER(state))
#define CORE_MARKER(state) ((state >> 16) & 0xFFFFFFFF)
#define EXSS_MARKER(state) (state & 0xFFFFFFFF)
/**
* Find the end of the current frame in the bitstream.
@ -48,20 +55,23 @@ static int dca_find_frame_end(DCAParseContext *pc1, const uint8_t *buf,
int buf_size)
{
int start_found, i;
uint32_t state;
uint64_t state;
ParseContext *pc = &pc1->pc;
start_found = pc->frame_start_found;
state = pc->state;
state = pc->state64;
i = 0;
if (!start_found) {
for (i = 0; i < buf_size; i++) {
state = (state << 8) | buf[i];
if (IS_MARKER(state, i, buf, buf_size)) {
if (!pc1->lastmarker || state == pc1->lastmarker || pc1->lastmarker == DCA_SYNCWORD_SUBSTREAM) {
start_found = 1;
pc1->lastmarker = state;
if (IS_MARKER(state)) {
if (!pc1->lastmarker || CORE_MARKER(state) == pc1->lastmarker || pc1->lastmarker == DCA_SYNCWORD_SUBSTREAM) {
start_found = 1;
if (IS_EXSS_MARKER(state))
pc1->lastmarker = EXSS_MARKER(state);
else
pc1->lastmarker = CORE_MARKER(state);
i++;
break;
}
@ -72,20 +82,18 @@ static int dca_find_frame_end(DCAParseContext *pc1, const uint8_t *buf,
for (; i < buf_size; i++) {
pc1->size++;
state = (state << 8) | buf[i];
if (state == DCA_SYNCWORD_SUBSTREAM && !pc1->hd_pos)
pc1->hd_pos = pc1->size;
if (IS_MARKER(state, i, buf, buf_size) && (state == pc1->lastmarker || pc1->lastmarker == DCA_SYNCWORD_SUBSTREAM)) {
if (IS_MARKER(state) && (CORE_MARKER(state) == pc1->lastmarker || pc1->lastmarker == DCA_SYNCWORD_SUBSTREAM)) {
if (pc1->framesize > pc1->size)
continue;
pc->frame_start_found = 0;
pc->state = -1;
pc->state64 = -1;
pc1->size = 0;
return i - 3;
return IS_EXSS_MARKER(state) ? i - 3 : i - 5;
}
}
}
pc->frame_start_found = start_found;
pc->state = state;
pc->state64 = state;
return END_NOT_FOUND;
}