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ffmpeg/libavcodec/mlp_parser.c

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/*
* MLP parser
* Copyright (c) 2007 Ian Caulfield
*
* 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
*/
/**
* @file mlp_parser.c
* MLP parser
*/
#include <stdint.h>
#include "libavutil/crc.h"
#include "bitstream.h"
#include "parser.h"
#include "mlp_parser.h"
static const uint8_t mlp_quants[16] = {
16, 20, 24, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
};
static const uint8_t mlp_channels[32] = {
1, 2, 3, 4, 3, 4, 5, 3, 4, 5, 4, 5, 6, 4, 5, 4,
5, 6, 5, 5, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
};
static const uint8_t thd_chancount[13] = {
// LR C LFE LRs LRvh LRc LRrs Cs Ts LRsd LRw Cvh LFE2
2, 1, 1, 2, 2, 2, 2, 1, 1, 2, 2, 1, 1
};
static int mlp_samplerate(int in)
{
if (in == 0xF)
return 0;
return (in & 8 ? 44100 : 48000) << (in & 7) ;
}
static int truehd_channels(int chanmap)
{
int channels = 0, i;
for (i = 0; i < 13; i++)
channels += thd_chancount[i] * ((chanmap >> i) & 1);
return channels;
}
static int crc_init = 0;
static AVCRC crc_2D[1024];
/** MLP uses checksums that seem to be based on the standard CRC algorithm, but
* are not (in implementation terms, the table lookup and XOR are reversed).
* We can implement this behavior using a standard av_crc on all but the
* last element, then XOR that with the last element.
*/
static uint16_t mlp_checksum16(const uint8_t *buf, unsigned int buf_size)
{
uint16_t crc;
if (!crc_init) {
av_crc_init(crc_2D, 0, 16, 0x002D, sizeof(crc_2D));
crc_init = 1;
}
crc = av_crc(crc_2D, 0, buf, buf_size - 2);
crc ^= AV_RL16(buf + buf_size - 2);
return crc;
}
/** Read a major sync info header - contains high level information about
* the stream - sample rate, channel arrangement etc. Most of this
* information is not actually necessary for decoding, only for playback.
* gb must be a freshly initialized GetBitContext with no bits read.
*/
int ff_mlp_read_major_sync(void *log, MLPHeaderInfo *mh, GetBitContext *gb)
{
int ratebits;
uint16_t checksum;
assert(get_bits_count(gb) == 0);
if (gb->size_in_bits < 28 << 3) {
av_log(log, AV_LOG_ERROR, "packet too short, unable to read major sync\n");
return -1;
}
checksum = mlp_checksum16(gb->buffer, 26);
if (checksum != AV_RL16(gb->buffer+26)) {
av_log(log, AV_LOG_ERROR, "major sync info header checksum error\n");
return -1;
}
if (get_bits_long(gb, 24) != 0xf8726f) /* Sync words */
return -1;
mh->stream_type = get_bits(gb, 8);
if (mh->stream_type == 0xbb) {
mh->group1_bits = mlp_quants[get_bits(gb, 4)];
mh->group2_bits = mlp_quants[get_bits(gb, 4)];
ratebits = get_bits(gb, 4);
mh->group1_samplerate = mlp_samplerate(ratebits);
mh->group2_samplerate = mlp_samplerate(get_bits(gb, 4));
skip_bits(gb, 11);
mh->channels_mlp = get_bits(gb, 5);
} else if (mh->stream_type == 0xba) {
mh->group1_bits = 24; // TODO: Is this information actually conveyed anywhere?
mh->group2_bits = 0;
ratebits = get_bits(gb, 4);
mh->group1_samplerate = mlp_samplerate(ratebits);
mh->group2_samplerate = 0;
skip_bits(gb, 8);
mh->channels_thd_stream1 = get_bits(gb, 5);
skip_bits(gb, 2);
mh->channels_thd_stream2 = get_bits(gb, 13);
} else
return -1;
mh->access_unit_size = 40 << (ratebits & 7);
mh->access_unit_size_pow2 = 64 << (ratebits & 7);
skip_bits_long(gb, 48);
mh->is_vbr = get_bits1(gb);
mh->peak_bitrate = (get_bits(gb, 15) * mh->group1_samplerate + 8) >> 4;
mh->num_substreams = get_bits(gb, 4);
skip_bits_long(gb, 4 + 11 * 8);
return 0;
}
typedef struct MLPParseContext
{
ParseContext pc;
int bytes_left;
int in_sync;
int num_substreams;
} MLPParseContext;
static int mlp_parse(AVCodecParserContext *s,
AVCodecContext *avctx,
const uint8_t **poutbuf, int *poutbuf_size,
const uint8_t *buf, int buf_size)
{
MLPParseContext *mp = s->priv_data;
int sync_present;
uint8_t parity_bits;
int next;
int i, p = 0;
*poutbuf_size = 0;
if (buf_size == 0)
return 0;
if (!mp->in_sync) {
// Not in sync - find a major sync header
for (i = 0; i < buf_size; i++) {
mp->pc.state = (mp->pc.state << 8) | buf[i];
if ((mp->pc.state & 0xfffffffe) == 0xf8726fba) {
mp->in_sync = 1;
mp->bytes_left = 0;
break;
}
}
if (!mp->in_sync) {
ff_combine_frame(&mp->pc, END_NOT_FOUND, &buf, &buf_size);
return buf_size;
}
ff_combine_frame(&mp->pc, i - 7, &buf, &buf_size);
return i - 7;
}
if (mp->bytes_left == 0) {
// Find length of this packet
/* Copy overread bytes from last frame into buffer. */
for(; mp->pc.overread>0; mp->pc.overread--) {
mp->pc.buffer[mp->pc.index++]= mp->pc.buffer[mp->pc.overread_index++];
}
if (mp->pc.index + buf_size < 2) {
ff_combine_frame(&mp->pc, END_NOT_FOUND, &buf, &buf_size);
return buf_size;
}
mp->bytes_left = ((mp->pc.index > 0 ? mp->pc.buffer[0] : buf[0]) << 8)
| (mp->pc.index > 1 ? mp->pc.buffer[1] : buf[1-mp->pc.index]);
mp->bytes_left = (mp->bytes_left & 0xfff) * 2;
mp->bytes_left -= mp->pc.index;
}
next = (mp->bytes_left > buf_size) ? END_NOT_FOUND : mp->bytes_left;
if (ff_combine_frame(&mp->pc, next, &buf, &buf_size) < 0) {
mp->bytes_left -= buf_size;
return buf_size;
}
mp->bytes_left = 0;
sync_present = (AV_RB32(buf + 4) & 0xfffffffe) == 0xf8726fba;
if (!sync_present) {
/* The first nibble of a frame is a parity check of the 4-byte
* access unit header and all the 2- or 4-byte substream headers. */
// Only check when this isn't a sync frame - syncs have a checksum.
parity_bits = 0;
for (i = -1; i < mp->num_substreams; i++) {
parity_bits ^= buf[p++];
parity_bits ^= buf[p++];
if (i < 0 || buf[p-2] & 0x80) {
parity_bits ^= buf[p++];
parity_bits ^= buf[p++];
}
}
if ((((parity_bits >> 4) ^ parity_bits) & 0xF) != 0xF) {
av_log(avctx, AV_LOG_INFO, "mlpparse: Parity check failed.\n");
goto lost_sync;
}
} else {
GetBitContext gb;
MLPHeaderInfo mh;
init_get_bits(&gb, buf + 4, (buf_size - 4) << 3);
if (ff_mlp_read_major_sync(avctx, &mh, &gb) < 0)
goto lost_sync;
#ifdef CONFIG_AUDIO_NONSHORT
avctx->bits_per_sample = mh.group1_bits;
if (avctx->bits_per_sample > 16)
avctx->sample_fmt = SAMPLE_FMT_S32;
#endif
avctx->sample_rate = mh.group1_samplerate;
avctx->frame_size = mh.access_unit_size;
if (mh.stream_type == 0xbb) {
/* MLP stream */
avctx->channels = mlp_channels[mh.channels_mlp];
} else { /* mh.stream_type == 0xba */
/* TrueHD stream */
if (mh.channels_thd_stream2)
avctx->channels = truehd_channels(mh.channels_thd_stream2);
else
avctx->channels = truehd_channels(mh.channels_thd_stream1);
}
if (!mh.is_vbr) /* Stream is CBR */
avctx->bit_rate = mh.peak_bitrate;
mp->num_substreams = mh.num_substreams;
}
*poutbuf = buf;
*poutbuf_size = buf_size;
return next;
lost_sync:
mp->in_sync = 0;
return 1;
}
AVCodecParser mlp_parser = {
{ CODEC_ID_MLP },
sizeof(MLPParseContext),
NULL,
mlp_parse,
NULL,
};
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