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ffmpeg/libavformat/mpeg.c

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/*
* MPEG1/2 mux/demux
* Copyright (c) 2000, 2001, 2002 Fabrice Bellard.
*
* This library 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 of the License, or (at your option) any later version.
*
* This library 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 this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include "avformat.h"
#define MAX_PAYLOAD_SIZE 4096
#define NB_STREAMS 2
typedef struct {
uint8_t buffer[MAX_PAYLOAD_SIZE];
int buffer_ptr;
uint8_t id;
int max_buffer_size; /* in bytes */
int packet_number;
int64_t start_pts;
} StreamInfo;
typedef struct {
int packet_size; /* required packet size */
int packet_data_max_size; /* maximum data size inside a packet */
int packet_number;
int pack_header_freq; /* frequency (in packets^-1) at which we send pack headers */
int system_header_freq;
int mux_rate; /* bitrate in units of 50 bytes/s */
/* stream info */
int audio_bound;
int video_bound;
int is_mpeg2;
int is_vcd;
} MpegMuxContext;
#define PACK_START_CODE ((unsigned int)0x000001ba)
#define SYSTEM_HEADER_START_CODE ((unsigned int)0x000001bb)
#define SEQUENCE_END_CODE ((unsigned int)0x000001b7)
#define PACKET_START_CODE_MASK ((unsigned int)0xffffff00)
#define PACKET_START_CODE_PREFIX ((unsigned int)0x00000100)
#define ISO_11172_END_CODE ((unsigned int)0x000001b9)
/* mpeg2 */
#define PROGRAM_STREAM_MAP 0x1bc
#define PRIVATE_STREAM_1 0x1bd
#define PADDING_STREAM 0x1be
#define PRIVATE_STREAM_2 0x1bf
#define AUDIO_ID 0xc0
#define VIDEO_ID 0xe0
extern AVOutputFormat mpeg1system_mux;
extern AVOutputFormat mpeg1vcd_mux;
extern AVOutputFormat mpeg2vob_mux;
static int put_pack_header(AVFormatContext *ctx,
uint8_t *buf, int64_t timestamp)
{
MpegMuxContext *s = ctx->priv_data;
PutBitContext pb;
init_put_bits(&pb, buf, 128, NULL, NULL);
put_bits(&pb, 32, PACK_START_CODE);
if (s->is_mpeg2) {
put_bits(&pb, 2, 0x1);
} else {
put_bits(&pb, 4, 0x2);
}
put_bits(&pb, 3, (uint32_t)((timestamp >> 30) & 0x07));
put_bits(&pb, 1, 1);
put_bits(&pb, 15, (uint32_t)((timestamp >> 15) & 0x7fff));
put_bits(&pb, 1, 1);
put_bits(&pb, 15, (uint32_t)((timestamp) & 0x7fff));
put_bits(&pb, 1, 1);
if (s->is_mpeg2) {
/* clock extension */
put_bits(&pb, 9, 0);
put_bits(&pb, 1, 1);
}
put_bits(&pb, 1, 1);
put_bits(&pb, 22, s->mux_rate);
put_bits(&pb, 1, 1);
if (s->is_mpeg2) {
put_bits(&pb, 5, 0x1f); /* reserved */
put_bits(&pb, 3, 0); /* stuffing length */
}
flush_put_bits(&pb);
return pbBufPtr(&pb) - pb.buf;
}
static int put_system_header(AVFormatContext *ctx, uint8_t *buf)
{
MpegMuxContext *s = ctx->priv_data;
int size, rate_bound, i, private_stream_coded, id;
PutBitContext pb;
init_put_bits(&pb, buf, 128, NULL, NULL);
put_bits(&pb, 32, SYSTEM_HEADER_START_CODE);
put_bits(&pb, 16, 0);
put_bits(&pb, 1, 1);
rate_bound = s->mux_rate; /* maximum bit rate of the multiplexed stream */
put_bits(&pb, 22, rate_bound);
put_bits(&pb, 1, 1); /* marker */
put_bits(&pb, 6, s->audio_bound);
put_bits(&pb, 1, 1); /* variable bitrate */
put_bits(&pb, 1, 1); /* non constrainted bit stream */
put_bits(&pb, 1, 0); /* audio locked */
put_bits(&pb, 1, 0); /* video locked */
put_bits(&pb, 1, 1); /* marker */
put_bits(&pb, 5, s->video_bound);
put_bits(&pb, 8, 0xff); /* reserved byte */
/* audio stream info */
private_stream_coded = 0;
for(i=0;i<ctx->nb_streams;i++) {
StreamInfo *stream = ctx->streams[i]->priv_data;
id = stream->id;
if (id < 0xc0) {
/* special case for private streams (AC3 use that) */
if (private_stream_coded)
continue;
private_stream_coded = 1;
id = 0xbd;
}
put_bits(&pb, 8, id); /* stream ID */
put_bits(&pb, 2, 3);
if (id < 0xe0) {
/* audio */
put_bits(&pb, 1, 0);
put_bits(&pb, 13, stream->max_buffer_size / 128);
} else {
/* video */
put_bits(&pb, 1, 1);
put_bits(&pb, 13, stream->max_buffer_size / 1024);
}
}
flush_put_bits(&pb);
size = pbBufPtr(&pb) - pb.buf;
/* patch packet size */
buf[4] = (size - 6) >> 8;
buf[5] = (size - 6) & 0xff;
return size;
}
static int mpeg_mux_init(AVFormatContext *ctx)
{
MpegMuxContext *s = ctx->priv_data;
int bitrate, i, mpa_id, mpv_id, ac3_id;
AVStream *st;
StreamInfo *stream;
s->packet_number = 0;
s->is_vcd = (ctx->oformat == &mpeg1vcd_mux);
s->is_mpeg2 = (ctx->oformat == &mpeg2vob_mux);
if (s->is_vcd)
s->packet_size = 2324; /* VCD packet size */
else
s->packet_size = 2048;
/* startcode(4) + length(2) + flags(1) */
s->packet_data_max_size = s->packet_size - 7;
s->audio_bound = 0;
s->video_bound = 0;
mpa_id = AUDIO_ID;
ac3_id = 0x80;
mpv_id = VIDEO_ID;
for(i=0;i<ctx->nb_streams;i++) {
st = ctx->streams[i];
stream = av_mallocz(sizeof(StreamInfo));
if (!stream)
goto fail;
st->priv_data = stream;
switch(st->codec.codec_type) {
case CODEC_TYPE_AUDIO:
if (st->codec.codec_id == CODEC_ID_AC3)
stream->id = ac3_id++;
else
stream->id = mpa_id++;
stream->max_buffer_size = 4 * 1024;
s->audio_bound++;
break;
case CODEC_TYPE_VIDEO:
stream->id = mpv_id++;
stream->max_buffer_size = 46 * 1024;
s->video_bound++;
break;
default:
av_abort();
}
}
/* we increase slightly the bitrate to take into account the
headers. XXX: compute it exactly */
bitrate = 2000;
for(i=0;i<ctx->nb_streams;i++) {
st = ctx->streams[i];
bitrate += st->codec.bit_rate;
}
s->mux_rate = (bitrate + (8 * 50) - 1) / (8 * 50);
if (s->is_vcd || s->is_mpeg2)
/* every packet */
s->pack_header_freq = 1;
else
/* every 2 seconds */
s->pack_header_freq = 2 * bitrate / s->packet_size / 8;
if (s->is_mpeg2)
/* every 200 packets. Need to look at the spec. */
s->system_header_freq = s->pack_header_freq * 40;
else if (s->is_vcd)
/* every 40 packets, this is my invention */
s->system_header_freq = s->pack_header_freq * 40;
else
s->system_header_freq = s->pack_header_freq * 5;
for(i=0;i<ctx->nb_streams;i++) {
stream = ctx->streams[i]->priv_data;
stream->buffer_ptr = 0;
stream->packet_number = 0;
stream->start_pts = -1;
}
return 0;
fail:
for(i=0;i<ctx->nb_streams;i++) {
av_free(ctx->streams[i]->priv_data);
}
return -ENOMEM;
}
/* flush the packet on stream stream_index */
static void flush_packet(AVFormatContext *ctx, int stream_index)
{
MpegMuxContext *s = ctx->priv_data;
StreamInfo *stream = ctx->streams[stream_index]->priv_data;
uint8_t *buf_ptr;
int size, payload_size, startcode, id, len, stuffing_size, i, header_len;
int64_t timestamp;
uint8_t buffer[128];
id = stream->id;
timestamp = stream->start_pts;
#if 0
printf("packet ID=%2x PTS=%0.3f\n",
id, timestamp / 90000.0);
#endif
buf_ptr = buffer;
if (((s->packet_number % s->pack_header_freq) == 0)) {
/* output pack and systems header if needed */
size = put_pack_header(ctx, buf_ptr, timestamp);
buf_ptr += size;
if ((s->packet_number % s->system_header_freq) == 0) {
size = put_system_header(ctx, buf_ptr);
buf_ptr += size;
}
}
size = buf_ptr - buffer;
put_buffer(&ctx->pb, buffer, size);
/* packet header */
if (s->is_mpeg2) {
header_len = 8;
} else {
header_len = 5;
}
payload_size = s->packet_size - (size + 6 + header_len);
if (id < 0xc0) {
startcode = PRIVATE_STREAM_1;
payload_size -= 4;
} else {
startcode = 0x100 + id;
}
stuffing_size = payload_size - stream->buffer_ptr;
if (stuffing_size < 0)
stuffing_size = 0;
put_be32(&ctx->pb, startcode);
put_be16(&ctx->pb, payload_size + header_len);
/* stuffing */
for(i=0;i<stuffing_size;i++)
put_byte(&ctx->pb, 0xff);
if (s->is_mpeg2) {
put_byte(&ctx->pb, 0x80); /* mpeg2 id */
put_byte(&ctx->pb, 0x80); /* flags */
put_byte(&ctx->pb, 0x05); /* header len (only pts is included) */
}
put_byte(&ctx->pb,
(0x02 << 4) |
(((timestamp >> 30) & 0x07) << 1) |
1);
put_be16(&ctx->pb, (uint16_t)((((timestamp >> 15) & 0x7fff) << 1) | 1));
put_be16(&ctx->pb, (uint16_t)((((timestamp) & 0x7fff) << 1) | 1));
if (startcode == PRIVATE_STREAM_1) {
put_byte(&ctx->pb, id);
if (id >= 0x80 && id <= 0xbf) {
/* XXX: need to check AC3 spec */
put_byte(&ctx->pb, 1);
put_byte(&ctx->pb, 0);
put_byte(&ctx->pb, 2);
}
}
/* output data */
put_buffer(&ctx->pb, stream->buffer, payload_size - stuffing_size);
put_flush_packet(&ctx->pb);
/* preserve remaining data */
len = stream->buffer_ptr - payload_size;
if (len < 0)
len = 0;
memmove(stream->buffer, stream->buffer + stream->buffer_ptr - len, len);
stream->buffer_ptr = len;
s->packet_number++;
stream->packet_number++;
stream->start_pts = -1;
}
static int mpeg_mux_write_packet(AVFormatContext *ctx, int stream_index,
const uint8_t *buf, int size, int64_t pts)
{
MpegMuxContext *s = ctx->priv_data;
AVStream *st = ctx->streams[stream_index];
StreamInfo *stream = st->priv_data;
int len;
while (size > 0) {
/* set pts */
if (stream->start_pts == -1) {
stream->start_pts = pts;
}
len = s->packet_data_max_size - stream->buffer_ptr;
if (len > size)
len = size;
memcpy(stream->buffer + stream->buffer_ptr, buf, len);
stream->buffer_ptr += len;
buf += len;
size -= len;
while (stream->buffer_ptr >= s->packet_data_max_size) {
/* output the packet */
if (stream->start_pts == -1)
stream->start_pts = pts;
flush_packet(ctx, stream_index);
}
}
return 0;
}
static int mpeg_mux_end(AVFormatContext *ctx)
{
StreamInfo *stream;
int i;
/* flush each packet */
for(i=0;i<ctx->nb_streams;i++) {
stream = ctx->streams[i]->priv_data;
if (stream->buffer_ptr > 0) {
flush_packet(ctx, i);
}
}
/* End header according to MPEG1 systems standard. We do not write
it as it is usually not needed by decoders and because it
complicates MPEG stream concatenation. */
//put_be32(&ctx->pb, ISO_11172_END_CODE);
//put_flush_packet(&ctx->pb);
for(i=0;i<ctx->nb_streams;i++)
av_freep(&ctx->streams[i]->priv_data);
return 0;
}
/*********************************************/
/* demux code */
#define MAX_SYNC_SIZE 100000
static int mpegps_probe(AVProbeData *p)
{
int code, c, i;
code = 0xff;
/* we search the first start code. If it is a packet start code,
then we decide it is mpeg ps. We do not send highest value to
give a chance to mpegts */
/* NOTE: the search range was restricted to avoid too many false
detections */
if (p->buf_size < 6)
return 0;
for (i = 0; i < 20; i++) {
c = p->buf[i];
code = (code << 8) | c;
if ((code & 0xffffff00) == 0x100) {
if (code == PACK_START_CODE ||
code == SYSTEM_HEADER_START_CODE ||
(code >= 0x1e0 && code <= 0x1ef) ||
(code >= 0x1c0 && code <= 0x1df) ||
code == PRIVATE_STREAM_2 ||
code == PROGRAM_STREAM_MAP ||
code == PRIVATE_STREAM_1 ||
code == PADDING_STREAM)
return AVPROBE_SCORE_MAX - 2;
else
return 0;
}
}
return 0;
}
typedef struct MpegDemuxContext {
int header_state;
} MpegDemuxContext;
static int find_start_code(ByteIOContext *pb, int *size_ptr,
uint32_t *header_state)
{
unsigned int state, v;
int val, n;
state = *header_state;
n = *size_ptr;
while (n > 0) {
if (url_feof(pb))
break;
v = get_byte(pb);
n--;
if (state == 0x000001) {
state = ((state << 8) | v) & 0xffffff;
val = state;
goto found;
}
state = ((state << 8) | v) & 0xffffff;
}
val = -1;
found:
*header_state = state;
*size_ptr = n;
return val;
}
static int mpegps_read_header(AVFormatContext *s,
AVFormatParameters *ap)
{
MpegDemuxContext *m = s->priv_data;
m->header_state = 0xff;
/* no need to do more */
return 0;
}
static int64_t get_pts(ByteIOContext *pb, int c)
{
int64_t pts;
int val;
if (c < 0)
c = get_byte(pb);
pts = (int64_t)((c >> 1) & 0x07) << 30;
val = get_be16(pb);
pts |= (int64_t)(val >> 1) << 15;
val = get_be16(pb);
pts |= (int64_t)(val >> 1);
return pts;
}
static int mpegps_read_packet(AVFormatContext *s,
AVPacket *pkt)
{
MpegDemuxContext *m = s->priv_data;
AVStream *st;
int len, size, startcode, i, c, flags, header_len, type, codec_id;
int64_t pts, dts;
/* next start code (should be immediately after) */
redo:
m->header_state = 0xff;
size = MAX_SYNC_SIZE;
startcode = find_start_code(&s->pb, &size, &m->header_state);
//printf("startcode=%x pos=0x%Lx\n", startcode, url_ftell(&s->pb));
if (startcode < 0)
return -EIO;
if (startcode == PACK_START_CODE)
goto redo;
if (startcode == SYSTEM_HEADER_START_CODE)
goto redo;
if (startcode == PADDING_STREAM ||
startcode == PRIVATE_STREAM_2) {
/* skip them */
len = get_be16(&s->pb);
url_fskip(&s->pb, len);
goto redo;
}
/* find matching stream */
if (!((startcode >= 0x1c0 && startcode <= 0x1df) ||
(startcode >= 0x1e0 && startcode <= 0x1ef) ||
(startcode == 0x1bd)))
goto redo;
len = get_be16(&s->pb);
pts = AV_NOPTS_VALUE;
dts = AV_NOPTS_VALUE;
/* stuffing */
for(;;) {
c = get_byte(&s->pb);
len--;
/* XXX: for mpeg1, should test only bit 7 */
if (c != 0xff)
break;
}
if ((c & 0xc0) == 0x40) {
/* buffer scale & size */
get_byte(&s->pb);
c = get_byte(&s->pb);
len -= 2;
}
if ((c & 0xf0) == 0x20) {
pts = get_pts(&s->pb, c);
len -= 4;
} else if ((c & 0xf0) == 0x30) {
pts = get_pts(&s->pb, c);
dts = get_pts(&s->pb, -1);
len -= 9;
} else if ((c & 0xc0) == 0x80) {
/* mpeg 2 PES */
if ((c & 0x30) != 0) {
fprintf(stderr, "Encrypted multiplex not handled\n");
return -EIO;
}
flags = get_byte(&s->pb);
header_len = get_byte(&s->pb);
len -= 2;
if (header_len > len)
goto redo;
if ((flags & 0xc0) == 0x80) {
pts = get_pts(&s->pb, -1);
header_len -= 5;
len -= 5;
} if ((flags & 0xc0) == 0xc0) {
pts = get_pts(&s->pb, -1);
dts = get_pts(&s->pb, -1);
header_len -= 10;
len -= 10;
}
len -= header_len;
while (header_len > 0) {
get_byte(&s->pb);
header_len--;
}
}
if (startcode == 0x1bd) {
startcode = get_byte(&s->pb);
len--;
if (startcode >= 0x80 && startcode <= 0xbf) {
/* audio: skip header */
get_byte(&s->pb);
get_byte(&s->pb);
get_byte(&s->pb);
len -= 3;
}
}
/* now find stream */
for(i=0;i<s->nb_streams;i++) {
st = s->streams[i];
if (st->id == startcode)
goto found;
}
if (startcode >= 0x1e0 && startcode <= 0x1ef) {
type = CODEC_TYPE_VIDEO;
codec_id = CODEC_ID_MPEG1VIDEO;
} else if (startcode >= 0x1c0 && startcode <= 0x1df) {
type = CODEC_TYPE_AUDIO;
codec_id = CODEC_ID_MP2;
} else if (startcode >= 0x80 && startcode <= 0x9f) {
type = CODEC_TYPE_AUDIO;
codec_id = CODEC_ID_AC3;
} else if (startcode >= 0xa0 && startcode <= 0xbf) {
type = CODEC_TYPE_AUDIO;
codec_id = CODEC_ID_PCM_S16BE;
} else {
skip:
/* skip packet */
url_fskip(&s->pb, len);
goto redo;
}
/* no stream found: add a new stream */
st = av_new_stream(s, startcode);
if (!st)
goto skip;
st->codec.codec_type = type;
st->codec.codec_id = codec_id;
found:
if (startcode >= 0xa0 && startcode <= 0xbf) {
int b1, freq;
static const int lpcm_freq_tab[4] = { 48000, 96000, 44100, 32000 };
/* for LPCM, we just skip the header and consider it is raw
audio data */
if (len <= 3)
goto skip;
get_byte(&s->pb); /* emphasis (1), muse(1), reserved(1), frame number(5) */
b1 = get_byte(&s->pb); /* quant (2), freq(2), reserved(1), channels(3) */
get_byte(&s->pb); /* dynamic range control (0x80 = off) */
len -= 3;
freq = (b1 >> 4) & 3;
st->codec.sample_rate = lpcm_freq_tab[freq];
st->codec.channels = 1 + (b1 & 7);
st->codec.bit_rate = st->codec.channels * st->codec.sample_rate * 2;
}
av_new_packet(pkt, len);
//printf("\nRead Packet ID: %x PTS: %f Size: %d", startcode,
// (float)pts/90000, len);
get_buffer(&s->pb, pkt->data, pkt->size);
pkt->pts = pts;
pkt->stream_index = st->index;
return 0;
}
static int mpegps_read_close(AVFormatContext *s)
{
return 0;
}
static AVOutputFormat mpeg1system_mux = {
"mpeg",
"MPEG1 System format",
"video/mpeg",
"mpg,mpeg",
sizeof(MpegMuxContext),
CODEC_ID_MP2,
CODEC_ID_MPEG1VIDEO,
mpeg_mux_init,
mpeg_mux_write_packet,
mpeg_mux_end,
};
static AVOutputFormat mpeg1vcd_mux = {
"vcd",
"MPEG1 System format (VCD)",
"video/mpeg",
NULL,
sizeof(MpegMuxContext),
CODEC_ID_MP2,
CODEC_ID_MPEG1VIDEO,
mpeg_mux_init,
mpeg_mux_write_packet,
mpeg_mux_end,
};
static AVOutputFormat mpeg2vob_mux = {
"vob",
"MPEG2 PS format (VOB)",
"video/mpeg",
"vob",
sizeof(MpegMuxContext),
CODEC_ID_MP2,
CODEC_ID_MPEG1VIDEO,
mpeg_mux_init,
mpeg_mux_write_packet,
mpeg_mux_end,
};
AVInputFormat mpegps_demux = {
"mpeg",
"MPEG PS format",
sizeof(MpegDemuxContext),
mpegps_probe,
mpegps_read_header,
mpegps_read_packet,
mpegps_read_close,
.flags = AVFMT_NOHEADER,
};
int mpegps_init(void)
{
av_register_output_format(&mpeg1system_mux);
av_register_output_format(&mpeg1vcd_mux);
av_register_output_format(&mpeg2vob_mux);
av_register_input_format(&mpegps_demux);
return 0;
}
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