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FFmpeg/libavcodec/dca_parser.c
foo86 a0349ae27c avcodec/dca_parser: improve frame end search 
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>
2016-05-20 16:36:08 -03:00

252 lines
8.1 KiB
C
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/*
* DCA parser
* Copyright (C) 2004 Gildas Bazin
* Copyright (C) 2004 Benjamin Zores
* Copyright (C) 2006 Benjamin Larsson
* Copyright (C) 2007 Konstantin Shishkov
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "dca.h"
#include "dca_syncwords.h"
#include "get_bits.h"
#include "parser.h"
typedef struct DCAParseContext {
ParseContext pc;
uint32_t lastmarker;
int size;
int framesize;
} DCAParseContext;
#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)
#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
*/
static int dca_find_frame_end(DCAParseContext *pc1, const uint8_t *buf,
int buf_size)
{
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) {
for (i = 0; i < buf_size; i++) {
state = (state << 8) | buf[i];
if (IS_MARKER(state)) {
if (!pc1->lastmarker ||
pc1->lastmarker == CORE_MARKER(state) ||
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;
}
}
}
}
if (start_found) {
for (; i < buf_size; i++) {
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)) {
pc->frame_start_found = 0;
pc->state64 = -1;
pc1->size = 0;
return IS_EXSS_MARKER(state) ? i - 3 : i - 5;
}
}
}
pc->frame_start_found = start_found;
pc->state64 = state;
pc1->size = size;
return END_NOT_FOUND;
}
static av_cold int dca_parse_init(AVCodecParserContext *s)
{
DCAParseContext *pc1 = s->priv_data;
pc1->lastmarker = 0;
return 0;
}
static int dca_parse_params(const uint8_t *buf, int buf_size, int *duration,
int *sample_rate)
{
GetBitContext gb;
uint8_t hdr[12 + AV_INPUT_BUFFER_PADDING_SIZE] = { 0 };
int ret, sample_blocks;
if (buf_size < 12)
return AVERROR_INVALIDDATA;
if ((ret = avpriv_dca_convert_bitstream(buf, 12, hdr, 12)) < 0)
return ret;
init_get_bits(&gb, hdr, 96);
skip_bits_long(&gb, 39);
sample_blocks = get_bits(&gb, 7) + 1;
if (sample_blocks < 8)
return AVERROR_INVALIDDATA;
*duration = 256 * (sample_blocks / 8);
skip_bits(&gb, 20);
*sample_rate = avpriv_dca_sample_rates[get_bits(&gb, 4)];
if (*sample_rate == 0)
return AVERROR_INVALIDDATA;
return 0;
}
static int dca_parse(AVCodecParserContext *s, AVCodecContext *avctx,
const uint8_t **poutbuf, int *poutbuf_size,
const uint8_t *buf, int buf_size)
{
DCAParseContext *pc1 = s->priv_data;
ParseContext *pc = &pc1->pc;
int next, duration, sample_rate;
if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
next = buf_size;
} else {
next = dca_find_frame_end(pc1, buf, buf_size);
if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
*poutbuf = NULL;
*poutbuf_size = 0;
return buf_size;
}
}
/* read the duration and sample rate from the frame header */
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);
} else
s->duration = 0;
*poutbuf = buf;
*poutbuf_size = buf_size;
return next;
}
AVCodecParser ff_dca_parser = {
.codec_ids = { AV_CODEC_ID_DTS },
.priv_data_size = sizeof(DCAParseContext),
.parser_init = dca_parse_init,
.parser_parse = dca_parse,
.parser_close = ff_parse_close,
};
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