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Code Issues Releases Activity

avcodec/dca_parser: improve frame end search

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Parse core frame size directly when searching for frame end instead of
using value extracted from previous frame.

Account for unused bits when calculating sync word distance for 14-bit
streams to avoid alias sync detection.

Parse EXSS frame size and skip over EXSS frame to avoid alias sync
detection.

Signed-off-by: James Almer <jamrial@gmail.com>
This commit is contained in:
foo86 2016-05-13 12:48:28 +03:00 committed by James Almer
parent 39f7620d76
commit a0349ae27c
1 changed files with 80 additions and 14 deletions
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94
libavcodec/dca_parser.c
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@ -47,6 +47,14 @@ typedef struct DCAParseContext {
#define CORE_MARKER(state) ((state >> 16) & 0xFFFFFFFF)
#define EXSS_MARKER(state) (state & 0xFFFFFFFF)
#define STATE_LE(state) (((state & 0xFF00FF00) >> 8) | ((state & 0x00FF00FF) << 8))
#define STATE_14(state) (((state & 0x3FFF0000) >> 8) | ((state & 0x00003FFF) >> 6))
#define CORE_FRAMESIZE(state) (((state >> 4) & 0x3FFF) + 1)
#define EXSS_FRAMESIZE(state) ((state & 0x2000000000) ? \
((state >> 5) & 0xFFFFF) + 1 : \
((state >> 13) & 0x0FFFF) + 1)
/**
* Find the end of the current frame in the bitstream.
* @return the position of the first byte of the next frame, or -1
@ -54,12 +62,13 @@ typedef struct DCAParseContext {
static int dca_find_frame_end(DCAParseContext *pc1, const uint8_t *buf,
int buf_size)
{
int start_found, i;
int start_found, size, i;
uint64_t state;
ParseContext *pc = &pc1->pc;
start_found = pc->frame_start_found;
state = pc->state64;
size = pc1->size;
i = 0;
if (!start_found) {
@ -80,15 +89,75 @@ static int dca_find_frame_end(DCAParseContext *pc1, const uint8_t *buf,
}
}
}
if (start_found) {
for (; i < buf_size; i++) {
pc1->size++;
size++;
state = (state << 8) | buf[i];
if (start_found == 1) {
switch (pc1->lastmarker) {
case DCA_SYNCWORD_CORE_BE:
if (size == 2) {
pc1->framesize = CORE_FRAMESIZE(state);
start_found = 2;
}
break;
case DCA_SYNCWORD_CORE_LE:
if (size == 2) {
pc1->framesize = CORE_FRAMESIZE(STATE_LE(state));
start_found = 2;
}
break;
case DCA_SYNCWORD_CORE_14B_BE:
if (size == 4) {
pc1->framesize = CORE_FRAMESIZE(STATE_14(state)) * 8 / 14 * 2;
start_found = 2;
}
break;
case DCA_SYNCWORD_CORE_14B_LE:
if (size == 4) {
pc1->framesize = CORE_FRAMESIZE(STATE_14(STATE_LE(state))) * 8 / 14 * 2;
start_found = 2;
}
break;
case DCA_SYNCWORD_SUBSTREAM:
if (size == 6) {
pc1->framesize = EXSS_FRAMESIZE(state);
start_found = 2;
}
break;
default:
av_assert0(0);
}
continue;
}
if (pc1->lastmarker == DCA_SYNCWORD_CORE_BE) {
if (pc1->framesize > size + 2)
continue;
if (start_found == 2 && IS_EXSS_MARKER(state)) {
pc1->framesize = size + 2;
start_found = 3;
continue;
}
if (start_found == 3) {
if (size == pc1->framesize + 4) {
pc1->framesize += EXSS_FRAMESIZE(state);
start_found = 4;
}
continue;
}
}
if (pc1->framesize > size)
continue;
if (IS_MARKER(state) &&
(pc1->lastmarker == CORE_MARKER(state) ||
pc1->lastmarker == DCA_SYNCWORD_SUBSTREAM)) {
if (pc1->framesize > pc1->size)
continue;
pc->frame_start_found = 0;
pc->state64 = -1;
pc1->size = 0;
@ -96,8 +165,10 @@ static int dca_find_frame_end(DCAParseContext *pc1, const uint8_t *buf,
}
}
}
pc->frame_start_found = start_found;
pc->state64 = state;
pc1->size = size;
return END_NOT_FOUND;
}
@ -110,11 +181,11 @@ static av_cold int dca_parse_init(AVCodecParserContext *s)
}
static int dca_parse_params(const uint8_t *buf, int buf_size, int *duration,
int *sample_rate, int *framesize)
int *sample_rate)
{
GetBitContext gb;
uint8_t hdr[12 + AV_INPUT_BUFFER_PADDING_SIZE] = { 0 };
int ret, sample_blocks, sr_code;
int ret, sample_blocks;
if (buf_size < 12)
return AVERROR_INVALIDDATA;
@ -130,13 +201,8 @@ static int dca_parse_params(const uint8_t *buf, int buf_size, int *duration,
return AVERROR_INVALIDDATA;
*duration = 256 * (sample_blocks / 8);
*framesize = get_bits(&gb, 14) + 1;
if (*framesize < 95)
return AVERROR_INVALIDDATA;
skip_bits(&gb, 6);
sr_code = get_bits(&gb, 4);
*sample_rate = avpriv_dca_sample_rates[sr_code];
skip_bits(&gb, 20);
*sample_rate = avpriv_dca_sample_rates[get_bits(&gb, 4)];
if (*sample_rate == 0)
return AVERROR_INVALIDDATA;
@ -164,7 +230,7 @@ static int dca_parse(AVCodecParserContext *s, AVCodecContext *avctx,
}
/* read the duration and sample rate from the frame header */
if (!dca_parse_params(buf, buf_size, &duration, &sample_rate, &pc1->framesize)) {
if (!dca_parse_params(buf, buf_size, &duration, &sample_rate)) {
if (!avctx->sample_rate)
avctx->sample_rate = sample_rate;
s->duration = av_rescale(duration, avctx->sample_rate, sample_rate);