mpeg.c 17.8 KB
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/*
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 * MPEG1/2 demuxer
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 * Copyright (c) 2000, 2001, 2002 Fabrice Bellard
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 *
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 * This file is part of Libav.
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 *
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 * Libav is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * Libav is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with Libav; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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#include "avformat.h"
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#include "internal.h"
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#include "mpeg.h"
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#undef NDEBUG
#include <assert.h>

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

#define MAX_SYNC_SIZE 100000

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static int check_pes(uint8_t *p, uint8_t *end)
{
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    int pes1;
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    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;
    else if ((*p & 0xF0) == 0x30)
        pes1 = p[0] & p[2] & p[4] & p[5] & p[7] & p[9] & 1;
    else
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        pes1 = *p == 0x0F;

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    return pes1 || pes2;
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}

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static int check_pack_header(const uint8_t *buf)
{
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    return (buf[1] & 0xC0) == 0x40 || (buf[1] & 0xF0) == 0x20;
}

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static int mpegps_probe(AVProbeData *p)
{
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    uint32_t code = -1;
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    int i;
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    int sys = 0, pspack = 0, priv1 = 0, vid = 0;
    int audio = 0, invalid = 0, score = 0;
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    for (i = 0; i < p->buf_size; i++) {
        code = (code << 8) + p->buf[i];
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        if ((code & 0xffffff00) == 0x100) {
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            int len  = p->buf[i + 1] << 8 | p->buf[i + 2];
            int pes  = check_pes(p->buf + i, p->buf + p->buf_size);
            int pack = check_pack_header(p->buf + i);

            if (code == SYSTEM_HEADER_START_CODE)
                sys++;
            else if (code == PACK_START_CODE && pack)
                pspack++;
            else if ((code & 0xf0) == VIDEO_ID && pes)
                vid++;
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            // skip pes payload to avoid start code emulation for private
            // and audio streams
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            else if ((code & 0xe0) == AUDIO_ID && pes) {
                audio++;
                i += len;
            } else if (code == PRIVATE_STREAM_1 && pes) {
                priv1++;
                i += len;
            } else if ((code & 0xf0) == VIDEO_ID && !pes)
                invalid++;
            else if ((code & 0xe0) == AUDIO_ID && !pes)
                invalid++;
            else if (code == PRIVATE_STREAM_1 && !pes)
                invalid++;
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        }
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    }
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    if (vid + audio > invalid)   /* invalid VDR files nd short PES streams */
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        score = AVPROBE_SCORE_EXTENSION / 2;
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    if (sys > invalid && sys * 9 <= pspack * 10)
        return pspack > 2 ? AVPROBE_SCORE_EXTENSION + 2
                          : AVPROBE_SCORE_EXTENSION / 2; // 1 more than .mpg
    if (pspack > invalid && (priv1 + vid + audio) * 10 >= pspack * 9)
        return pspack > 2 ? AVPROBE_SCORE_EXTENSION + 2
                          : AVPROBE_SCORE_EXTENSION / 2; // 1 more than .mpg
    if ((!!vid ^ !!audio) && (audio > 4 || vid > 1) && !sys &&
        !pspack && p->buf_size > 2048 && vid + audio > invalid) /* PES stream */
        return (audio > 12 || vid > 3) ? AVPROBE_SCORE_EXTENSION + 2
                                       : AVPROBE_SCORE_EXTENSION / 2;

    // 02-Penguin.flac has sys:0 priv1:0 pspack:0 vid:0 audio:1
    // mp3_misidentified_2.mp3 has sys:0 priv1:0 pspack:0 vid:0 audio:6
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    return score;
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}

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

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static int mpegps_read_header(AVFormatContext *s)
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{
    MpegDemuxContext *m = s->priv_data;
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    const char *sofdec  = "Sofdec";
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    int v, i = 0;
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    m->header_state = 0xff;
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    s->ctx_flags   |= AVFMTCTX_NOHEADER;
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    m->sofdec = -1;
    do {
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        v = avio_r8(s->pb);
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        m->header_state = m->header_state << 8 | v;
        m->sofdec++;
    } while (v == sofdec[i] && i++ < 6);
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    m->sofdec = (m->sofdec == 6) ? 1 : 0;

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

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

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    buf[0] = c < 0 ? avio_r8(pb) : c;
    avio_read(pb, buf + 1, 4);
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    return ff_parse_pes_pts(buf);
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}

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static int find_next_start_code(AVIOContext *pb, int *size_ptr,
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                                int32_t *header_state)
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{
    unsigned int state, v;
    int val, n;

    state = *header_state;
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    n     = *size_ptr;
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    while (n > 0) {
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        if (pb->eof_reached)
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            break;
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        v = avio_r8(pb);
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        n--;
        if (state == 0x000001) {
            state = ((state << 8) | v) & 0xffffff;
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            val   = state;
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            goto found;
        }
        state = ((state << 8) | v) & 0xffffff;
    }
    val = -1;
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found:
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    *header_state = state;
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    *size_ptr     = n;
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    return val;
}

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

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    psm_length = avio_rb16(pb);
    avio_r8(pb);
    avio_r8(pb);
    ps_info_length = avio_rb16(pb);
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    /* skip program_stream_info */
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    avio_skip(pb, ps_info_length);
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    es_map_length = avio_rb16(pb);
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    /* at least one es available? */
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    while (es_map_length >= 4) {
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        unsigned char type      = avio_r8(pb);
        unsigned char es_id     = avio_r8(pb);
        uint16_t es_info_length = avio_rb16(pb);
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        /* remember mapping from stream id to stream type */
        m->psm_es_type[es_id] = type;
        /* skip program_stream_info */
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        avio_skip(pb, es_info_length);
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        es_map_length -= 4 + es_info_length;
    }
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    avio_rb32(pb); /* crc32 */
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    return 2 + psm_length;
}

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

error_redo:
    avio_seek(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 = avio_tell(s->pb);
    if (startcode < 0) {
        if (s->pb->eof_reached)
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            return AVERROR_EOF;
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        // FIXME we should remember header_state
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        return AVERROR(EAGAIN);
    }

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    if (startcode == PACK_START_CODE)
        goto redo;
    if (startcode == SYSTEM_HEADER_START_CODE)
        goto redo;
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    if (startcode == PADDING_STREAM) {
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        avio_skip(s->pb, avio_rb16(s->pb));
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        goto redo;
    }
    if (startcode == PRIVATE_STREAM_2) {
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        len = avio_rb16(s->pb);
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        if (!m->sofdec) {
            while (len-- >= 6) {
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                if (avio_r8(s->pb) == 'S') {
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                    uint8_t buf[5];
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                    avio_read(s->pb, buf, sizeof(buf));
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                    m->sofdec = !memcmp(buf, "ofdec", 5);
                    len -= sizeof(buf);
                    break;
                }
            }
            m->sofdec -= !m->sofdec;
        }
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        avio_skip(s->pb, len);
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        goto redo;
    }
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    if (startcode == PROGRAM_STREAM_MAP) {
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        mpegps_psm_parse(m, s->pb);
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        goto redo;
    }
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    /* find matching stream */
    if (!((startcode >= 0x1c0 && startcode <= 0x1df) ||
          (startcode >= 0x1e0 && startcode <= 0x1ef) ||
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          (startcode == 0x1bd) || (startcode == 0x1fd)))
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        goto redo;
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    if (ppos) {
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        *ppos = avio_tell(s->pb) - 4;
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    }
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    len = avio_rb16(s->pb);
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    pts =
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    dts = AV_NOPTS_VALUE;
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    /* stuffing */
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    for (;;) {
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        if (len < 1)
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            goto error_redo;
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        c = avio_r8(s->pb);
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        len--;
        /* XXX: for mpeg1, should test only bit 7 */
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        if (c != 0xff)
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            break;
    }
    if ((c & 0xc0) == 0x40) {
        /* buffer scale & size */
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        avio_r8(s->pb);
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        c    = avio_r8(s->pb);
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        len -= 2;
    }
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    if ((c & 0xe0) == 0x20) {
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        dts  =
        pts  = get_pts(s->pb, c);
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        len -= 4;
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        if (c & 0x10) {
            dts  = get_pts(s->pb, -1);
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            len -= 5;
        }
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    } else if ((c & 0xc0) == 0x80) {
        /* mpeg 2 PES */
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        flags      = avio_r8(s->pb);
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        header_len = avio_r8(s->pb);
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        len       -= 2;
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        if (header_len > len)
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            goto error_redo;
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        len -= header_len;
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        if (flags & 0x80) {
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            dts         = pts = get_pts(s->pb, -1);
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            header_len -= 5;
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            if (flags & 0x40) {
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                dts         = get_pts(s->pb, -1);
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                header_len -= 5;
            }
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        }
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        if (flags & 0x3f && header_len == 0) {
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            flags &= 0xC0;
            av_log(s, AV_LOG_WARNING, "Further flags set but no bytes left\n");
        }
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        if (flags & 0x01) { /* PES extension */
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            pes_ext = avio_r8(s->pb);
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            header_len--;
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            /* Skip PES private data, program packet sequence counter
             * and P-STD buffer */
            skip  = (pes_ext >> 4) & 0xb;
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            skip += skip & 0x9;
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            if (pes_ext & 0x40 || skip > header_len) {
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                av_log(s, AV_LOG_WARNING, "pes_ext %X is invalid\n", pes_ext);
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                pes_ext = skip = 0;
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            }
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            avio_skip(s->pb, skip);
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            header_len -= skip;

            if (pes_ext & 0x01) { /* PES extension 2 */
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                ext2_len = avio_r8(s->pb);
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                header_len--;
                if ((ext2_len & 0x7f) > 0) {
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                    id_ext = avio_r8(s->pb);
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                    if ((id_ext & 0x80) == 0)
                        startcode = ((startcode & 0xff) << 8) | id_ext;
                    header_len--;
                }
            }
        }
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        if (header_len < 0)
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            goto error_redo;
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        avio_skip(s->pb, header_len);
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    } else if (c != 0xf)
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        goto redo;

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    if (startcode == PRIVATE_STREAM_1 && !m->psm_es_type[startcode & 0xff]) {
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        startcode = avio_r8(s->pb);
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        len--;
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        if (startcode >= 0x80 && startcode <= 0xcf) {
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            /* audio: skip header */
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            avio_r8(s->pb);
            avio_r8(s->pb);
            avio_r8(s->pb);
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            len -= 3;
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            if (startcode >= 0xb0 && startcode <= 0xbf) {
                /* MLP/TrueHD audio has a 4-byte header */
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                avio_r8(s->pb);
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                len--;
            }
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        }
    }
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    if (len < 0)
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        goto error_redo;
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    if (dts != AV_NOPTS_VALUE && ppos) {
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        int i;
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        for (i = 0; i < s->nb_streams; i++) {
            if (startcode == s->streams[i]->id &&
                s->pb->seekable /* index useless on streams anyway */) {
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                ff_reduce_index(s, i);
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                av_add_index_entry(s->streams[i], *ppos, dts, 0, 0,
                                   AVINDEX_KEYFRAME /* FIXME keyframe? */);
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            }
        }
    }
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    *pstart_code = startcode;
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    *ppts        = pts;
    *pdts        = dts;
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    return len;
}

static int mpegps_read_packet(AVFormatContext *s,
                              AVPacket *pkt)
{
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    MpegDemuxContext *m = s->priv_data;
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    AVStream *st;
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    int len, startcode, i, es_type, ret;
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    enum AVCodecID codec_id = AV_CODEC_ID_NONE;
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    enum AVMediaType type;
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    int64_t pts, dts, dummy_pos; // dummy_pos is needed for the index building to work
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    uint8_t av_uninit(dvdaudio_substream_type);
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redo:
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    len = mpegps_read_pes_header(s, &dummy_pos, &startcode, &pts, &dts);
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    if (len < 0)
        return len;
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    if (startcode == 0x1bd) {
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        dvdaudio_substream_type = avio_r8(s->pb);
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        avio_skip(s->pb, 3);
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        len -= 4;
    }

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    /* now find stream */
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    for (i = 0; i < s->nb_streams; i++) {
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        st = s->streams[i];
        if (st->id == startcode)
            goto found;
    }
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    es_type = m->psm_es_type[startcode & 0xff];
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    if (es_type > 0 && es_type != STREAM_TYPE_PRIVATE_DATA) {
        if (es_type == STREAM_TYPE_VIDEO_MPEG1) {
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            codec_id = AV_CODEC_ID_MPEG2VIDEO;
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            type     = AVMEDIA_TYPE_VIDEO;
        } else if (es_type == STREAM_TYPE_VIDEO_MPEG2) {
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            codec_id = AV_CODEC_ID_MPEG2VIDEO;
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            type     = AVMEDIA_TYPE_VIDEO;
        } else if (es_type == STREAM_TYPE_AUDIO_MPEG1 ||
                   es_type == STREAM_TYPE_AUDIO_MPEG2) {
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            codec_id = AV_CODEC_ID_MP3;
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            type     = AVMEDIA_TYPE_AUDIO;
        } else if (es_type == STREAM_TYPE_AUDIO_AAC) {
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            codec_id = AV_CODEC_ID_AAC;
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            type     = AVMEDIA_TYPE_AUDIO;
        } else if (es_type == STREAM_TYPE_VIDEO_MPEG4) {
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            codec_id = AV_CODEC_ID_MPEG4;
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            type     = AVMEDIA_TYPE_VIDEO;
        } else if (es_type == STREAM_TYPE_VIDEO_H264) {
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            codec_id = AV_CODEC_ID_H264;
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            type     = AVMEDIA_TYPE_VIDEO;
        } else if (es_type == STREAM_TYPE_AUDIO_AC3) {
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            codec_id = AV_CODEC_ID_AC3;
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            type     = AVMEDIA_TYPE_AUDIO;
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        } else {
            goto skip;
        }
    } else if (startcode >= 0x1e0 && startcode <= 0x1ef) {
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        static const unsigned char avs_seqh[4] = { 0, 0, 1, 0xb0 };
        unsigned char buf[8];
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        avio_read(s->pb, buf, 8);
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        avio_seek(s->pb, -8, SEEK_CUR);
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        if (!memcmp(buf, avs_seqh, 4) && (buf[6] != 0 || buf[7] != 1))
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            codec_id = AV_CODEC_ID_CAVS;
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        else
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            codec_id = AV_CODEC_ID_PROBE;
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        type = AVMEDIA_TYPE_VIDEO;
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    } else if (startcode >= 0x1c0 && startcode <= 0x1df) {
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        type     = AVMEDIA_TYPE_AUDIO;
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        codec_id = m->sofdec > 0 ? AV_CODEC_ID_ADPCM_ADX : AV_CODEC_ID_MP2;
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    } else if (startcode >= 0x80 && startcode <= 0x87) {
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        type     = AVMEDIA_TYPE_AUDIO;
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        codec_id = AV_CODEC_ID_AC3;
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    } else if ((startcode >= 0x88 && startcode <= 0x8f) ||
               (startcode >= 0x98 && startcode <= 0x9f)) {
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        /* 0x90 - 0x97 is reserved for SDDS in DVD specs */
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        type     = AVMEDIA_TYPE_AUDIO;
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        codec_id = AV_CODEC_ID_DTS;
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    } else if (startcode >= 0xa0 && startcode <= 0xaf) {
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        type     = AVMEDIA_TYPE_AUDIO;
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        codec_id = AV_CODEC_ID_PCM_DVD;
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    } else if (startcode >= 0xb0 && startcode <= 0xbf) {
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        type     = AVMEDIA_TYPE_AUDIO;
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        codec_id = AV_CODEC_ID_TRUEHD;
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    } else if (startcode >= 0xc0 && startcode <= 0xcf) {
        /* Used for both AC-3 and E-AC-3 in EVOB files */
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        type     = AVMEDIA_TYPE_AUDIO;
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        codec_id = AV_CODEC_ID_AC3;
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    } else if (startcode >= 0x20 && startcode <= 0x3f) {
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        type     = AVMEDIA_TYPE_SUBTITLE;
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        codec_id = AV_CODEC_ID_DVD_SUBTITLE;
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    } else if (startcode >= 0xfd55 && startcode <= 0xfd5f) {
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        type     = AVMEDIA_TYPE_VIDEO;
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        codec_id = AV_CODEC_ID_VC1;
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    } else if (startcode == 0x1bd) {
        // check dvd audio substream type
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        type = AVMEDIA_TYPE_AUDIO;
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        switch (dvdaudio_substream_type & 0xe0) {
        case 0xa0:
            codec_id = AV_CODEC_ID_PCM_DVD;
            break;
        case 0x80:
            if ((dvdaudio_substream_type & 0xf8) == 0x88)
                codec_id = AV_CODEC_ID_DTS;
            else
                codec_id = AV_CODEC_ID_AC3;
            break;
        default:
            av_log(s, AV_LOG_ERROR, "Unknown 0x1bd sub-stream\n");
            goto skip;
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        }
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    } else {
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skip:
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        /* skip packet */
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        avio_skip(s->pb, len);
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        goto redo;
    }
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    /* no stream found: add a new stream */
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    st = avformat_new_stream(s, NULL);
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    if (!st)
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        goto skip;
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    st->id                = startcode;
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    st->codec->codec_type = type;
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    st->codec->codec_id   = codec_id;
    st->need_parsing      = AVSTREAM_PARSE_FULL;

found:
    if (st->discard >= AVDISCARD_ALL)
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        goto skip;
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    ret = av_get_packet(s->pb, pkt, len);
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    pkt->pts          = pts;
    pkt->dts          = dts;
    pkt->pos          = dummy_pos;
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    pkt->stream_index = st->index;
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    av_dlog(s, "%d: pts=%0.3f dts=%0.3f size=%d\n",
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            pkt->stream_index, pkt->pts / 90000.0, pkt->dts / 90000.0,
            pkt->size);
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    return (ret < 0) ? ret : 0;
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}

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static int64_t mpegps_read_dts(AVFormatContext *s, int stream_index,
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                               int64_t *ppos, int64_t pos_limit)
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{
    int len, startcode;
    int64_t pos, pts, dts;

    pos = *ppos;
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    if (avio_seek(s->pb, pos, SEEK_SET) < 0)
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        return AV_NOPTS_VALUE;

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    for (;;) {
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        len = mpegps_read_pes_header(s, &pos, &startcode, &pts, &dts);
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        if (len < 0) {
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            av_dlog(s, "none (ret=%d)\n", len);
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            return AV_NOPTS_VALUE;
        }
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        if (startcode == s->streams[stream_index]->id &&
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            dts != AV_NOPTS_VALUE) {
            break;
        }
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        avio_skip(s->pb, len);
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    }
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    av_dlog(s, "pos=0x%"PRIx64" dts=0x%"PRIx64" %0.3f\n",
            pos, dts, dts / 90000.0);
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    *ppos = pos;
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    return dts;
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}

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AVInputFormat ff_mpegps_demuxer = {
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    .name           = "mpeg",
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    .long_name      = NULL_IF_CONFIG_SMALL("MPEG-PS (MPEG-2 Program Stream)"),
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    .priv_data_size = sizeof(MpegDemuxContext),
    .read_probe     = mpegps_probe,
    .read_header    = mpegps_read_header,
    .read_packet    = mpegps_read_packet,
    .read_timestamp = mpegps_read_dts,
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    .flags          = AVFMT_SHOW_IDS | AVFMT_TS_DISCONT,
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};