mpeg.c.svn-base

mediastreamer2是开源的网络传输媒体流的库

/*
 * MPEG1/2 demuxer
 * Copyright (c) 2000, 2001, 2002 Fabrice Bellard.
 *
 * 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 "avformat.h"
#include "mpeg.h"

//#define DEBUG_SEEK

#undef NDEBUG
#include <assert.h>

/*********************************************/
/* demux code */

#define MAX_SYNC_SIZE 100000

static int check_pes(uint8_t *p, uint8_t *end){
    int pes1;
    int pes2=      (p[3] & 0xC0) == 0x80
                && (p[4] & 0xC0) != 0x40
                &&((p[4] & 0xC0) == 0x00 || (p[4]&0xC0)>>2 == (p[6]&0xF0));

    for(p+=3; p<end && *p == 0xFF; p++);
    if((*p&0xC0) == 0x40) p+=2;
    if((*p&0xF0) == 0x20){
        pes1= p[0]&p[2]&p[4]&1;
        p+=5;
    }else if((*p&0xF0) == 0x30){
        pes1= p[0]&p[2]&p[4]&p[5]&p[7]&p[9]&1;
        p+=10;
    }else
        pes1 = *p == 0x0F;

    return pes1||pes2;
}

static int mpegps_probe(AVProbeData *p)
{
    uint32_t code= -1;
    int sys=0, pspack=0, priv1=0, vid=0, audio=0, invalid=0;
    int i;
    int score=0;

    for(i=0; i<p->buf_size; i++){
        code = (code<<8) + p->buf[i];
        if ((code & 0xffffff00) == 0x100) {
            int pes= check_pes(p->buf+i, p->buf+p->buf_size);

            if(code == SYSTEM_HEADER_START_CODE) sys++;
            else if(code == PRIVATE_STREAM_1)    priv1++;
            else if(code == PACK_START_CODE)     pspack++;
            else if((code & 0xf0) == VIDEO_ID && pes) vid++;
            else if((code & 0xe0) == AUDIO_ID && pes) audio++;

            else if((code & 0xf0) == VIDEO_ID && !pes) invalid++;
            else if((code & 0xe0) == AUDIO_ID && !pes) invalid++;
        }
    }

    if(vid+audio > invalid)     /* invalid VDR files nd short PES streams */
        score= AVPROBE_SCORE_MAX/4;

//av_log(NULL, AV_LOG_ERROR, "%d %d %d %d %d len:%d\n", sys, priv1, pspack,vid, audio, p->buf_size);
    if(sys>invalid && sys*9 <= pspack*10)
        return AVPROBE_SCORE_MAX/2+2; // +1 for .mpg
    if(priv1 + vid + audio > invalid && (priv1+vid+audio)*9 <= pspack*10)
        return AVPROBE_SCORE_MAX/2+2; // +1 for .mpg
    if((!!vid ^ !!audio) && (audio+vid > 1) && !sys && !pspack && p->buf_size>2048) /* PES stream */
        return AVPROBE_SCORE_MAX/2+2;

    //02-Penguin.flac has sys:0 priv1:0 pspack:0 vid:0 audio:1
    return score;
}


typedef struct MpegDemuxContext {
    int32_t header_state;
    unsigned char psm_es_type[256];
    int sofdec;
} MpegDemuxContext;

static int mpegps_read_header(AVFormatContext *s,
                              AVFormatParameters *ap)
{
    MpegDemuxContext *m = s->priv_data;
    const char *sofdec = "Sofdec";
    int v, i = 0;

    m->header_state = 0xff;
    s->ctx_flags |= AVFMTCTX_NOHEADER;

    m->sofdec = -1;
    do {
        v = get_byte(s->pb);
        m->header_state = m->header_state << 8 | v;
        m->sofdec++;
    } while (v == sofdec[i] && i++ < 6);

    /* no need to do more */
    return 0;
}

static int64_t get_pts(ByteIOContext *pb, int c)
{
    uint8_t buf[5];

    buf[0] = c<0 ? get_byte(pb) : c;
    get_buffer(pb, buf+1, 4);

    return ff_parse_pes_pts(buf);
}

static int find_next_start_code(ByteIOContext *pb, int *size_ptr,
                                int32_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;
}

#if 0 /* unused, remove? */
/* XXX: optimize */
static int find_prev_start_code(ByteIOContext *pb, int *size_ptr)
{
    int64_t pos, pos_start;
    int max_size, start_code;

    max_size = *size_ptr;
    pos_start = url_ftell(pb);

    /* in order to go faster, we fill the buffer */
    pos = pos_start - 16386;
    if (pos < 0)
        pos = 0;
    url_fseek(pb, pos, SEEK_SET);
    get_byte(pb);

    pos = pos_start;
    for(;;) {
        pos--;
        if (pos < 0 || (pos_start - pos) >= max_size) {
            start_code = -1;
            goto the_end;
        }
        url_fseek(pb, pos, SEEK_SET);
        start_code = get_be32(pb);
        if ((start_code & 0xffffff00) == 0x100)
            break;
    }
 the_end:
    *size_ptr = pos_start - pos;
    return start_code;
}
#endif

/**
 * Extracts stream types from a program stream map
 * According to ISO/IEC 13818-1 ('MPEG-2 Systems') table 2-35
 *
 * @return number of bytes occupied by PSM in the bitstream
 */
static long mpegps_psm_parse(MpegDemuxContext *m, ByteIOContext *pb)
{
    int psm_length, ps_info_length, es_map_length;

    psm_length = get_be16(pb);
    get_byte(pb);
    get_byte(pb);
    ps_info_length = get_be16(pb);

    /* skip program_stream_info */
    url_fskip(pb, ps_info_length);
    es_map_length = get_be16(pb);

    /* at least one es available? */
    while (es_map_length >= 4){
        unsigned char type = get_byte(pb);
        unsigned char es_id = get_byte(pb);
        uint16_t es_info_length = get_be16(pb);
        /* remember mapping from stream id to stream type */
        m->psm_es_type[es_id] = type;
        /* skip program_stream_info */
        url_fskip(pb, es_info_length);
        es_map_length -= 4 + es_info_length;
    }
    get_be32(pb); /* crc32 */
    return 2 + psm_length;
}

/* read the next PES header. Return its position in ppos
   (if not NULL), and its start code, pts and dts.
 */
static int mpegps_read_pes_header(AVFormatContext *s,
                                  int64_t *ppos, int *pstart_code,
                                  int64_t *ppts, int64_t *pdts)
{
    MpegDemuxContext *m = s->priv_data;
    int len, size, startcode, c, flags, header_len;
    int pes_ext, ext2_len, id_ext, skip;
    int64_t pts, dts;
    int64_t last_sync= url_ftell(s->pb);

 error_redo:
        url_fseek(s->pb, last_sync, SEEK_SET);
 redo:
        /* next start code (should be immediately after) */
        m->header_state = 0xff;
        size = MAX_SYNC_SIZE;
        startcode = find_next_start_code(s->pb, &size, &m->header_state);
        last_sync = url_ftell(s->pb);
    //printf("startcode=%x pos=0x%"PRIx64"\n", startcode, url_ftell(s->pb));
    if (startcode < 0)
        return AVERROR(EIO);
    if (startcode == PACK_START_CODE)
        goto redo;
    if (startcode == SYSTEM_HEADER_START_CODE)
        goto redo;
    if (startcode == PADDING_STREAM) {
        url_fskip(s->pb, get_be16(s->pb));
        goto redo;
    }
    if (startcode == PRIVATE_STREAM_2) {
        len = get_be16(s->pb);
        if (!m->sofdec) {
            while (len-- >= 6) {
                if (get_byte(s->pb) == 'S') {
                    uint8_t buf[5];
                    get_buffer(s->pb, buf, sizeof(buf));
                    m->sofdec = !memcmp(buf, "ofdec", 5);
                    len -= sizeof(buf);
                    break;
                }
            }
            m->sofdec -= !m->sofdec;
        }
        url_fskip(s->pb, len);
        goto redo;
    }
    if (startcode == PROGRAM_STREAM_MAP) {
        mpegps_psm_parse(m, s->pb);
        goto redo;
    }

    /* find matching stream */
    if (!((startcode >= 0x1c0 && startcode <= 0x1df) ||
          (startcode >= 0x1e0 && startcode <= 0x1ef) ||
          (startcode == 0x1bd) || (startcode == 0x1fd)))
        goto redo;
    if (ppos) {
        *ppos = url_ftell(s->pb) - 4;
    }
    len = get_be16(s->pb);
    pts =
    dts = AV_NOPTS_VALUE;