mpegts.c

ffmpeg源码分析

static void pat_cb(void *opaque, const uint8_t *section, int section_len)
{
    MpegTSContext *ts = opaque;
    SectionHeader h1, *h = &h1;
    const uint8_t *p, *p_end;
    int sid, pmt_pid;

#ifdef DEBUG_SI
    printf("PAT:\n");
    av_hex_dump(stdout, (uint8_t *)section, section_len);
#endif
    p_end = section + section_len - 4;
    p = section;
    if (parse_section_header(h, &p, p_end) < 0)
        return;
    if (h->tid != PAT_TID)
        return;

    for(;;) {
        sid = get16(&p, p_end);
        if (sid < 0)
            break;
        pmt_pid = get16(&p, p_end) & 0x1fff;
        if (pmt_pid < 0)
            break;
#ifdef DEBUG_SI
        printf("sid=0x%x pid=0x%x\n", sid, pmt_pid);
#endif
        if (sid == 0x0000) {
            /* NIT info */
        } else {
            if (ts->req_sid == sid) {
                ts->pmt_filter = mpegts_open_section_filter(ts, pmt_pid,
                                                            pmt_cb, ts, 1);
                goto found;
            }
        }
    }
    /* not found */
    ts->set_service_cb(ts->set_service_opaque, -1);

 found:
    mpegts_close_filter(ts, ts->pat_filter);
    ts->pat_filter = NULL;
}

/* add all services found in the PAT */
static void pat_scan_cb(void *opaque, const uint8_t *section, int section_len)
{
    MpegTSContext *ts = opaque;
    SectionHeader h1, *h = &h1;
    const uint8_t *p, *p_end;
    int sid, pmt_pid;
    char *provider_name, *name;
    char buf[256];

#ifdef DEBUG_SI
    printf("PAT:\n");
    av_hex_dump(stdout, (uint8_t *)section, section_len);
#endif
    p_end = section + section_len - 4;
    p = section;
    if (parse_section_header(h, &p, p_end) < 0)
        return;
    if (h->tid != PAT_TID)
        return;

    for(;;) {
        sid = get16(&p, p_end);
        if (sid < 0)
            break;
        pmt_pid = get16(&p, p_end) & 0x1fff;
        if (pmt_pid < 0)
            break;
#ifdef DEBUG_SI
        printf("sid=0x%x pid=0x%x\n", sid, pmt_pid);
#endif
        if (sid == 0x0000) {
            /* NIT info */
        } else {
            /* add the service with a dummy name */
            snprintf(buf, sizeof(buf), "Service %x\n", sid);
            name = av_strdup(buf);
            provider_name = av_strdup("");
            if (name && provider_name) {
                new_service(ts, sid, provider_name, name);
            } else {
                av_freep(&name);
                av_freep(&provider_name);
            }
        }
    }
    ts->stop_parse = 1;

    /* remove filter */
    mpegts_close_filter(ts, ts->pat_filter);
    ts->pat_filter = NULL;
}

void mpegts_set_service(MpegTSContext *ts, int sid,
                        SetServiceCallback *set_service_cb, void *opaque)
{
    ts->set_service_cb = set_service_cb;
    ts->set_service_opaque = opaque;
    ts->req_sid = sid;
    ts->pat_filter = mpegts_open_section_filter(ts, PAT_PID,
                                                pat_cb, ts, 1);
}

static void sdt_cb(void *opaque, const uint8_t *section, int section_len)
{
    MpegTSContext *ts = opaque;
    SectionHeader h1, *h = &h1;
    const uint8_t *p, *p_end, *desc_list_end, *desc_end;
    int onid, val, sid, desc_list_len, desc_tag, desc_len, service_type;
    char *name, *provider_name;

#ifdef DEBUG_SI
    printf("SDT:\n");
    av_hex_dump(stdout, (uint8_t *)section, section_len);
#endif

    p_end = section + section_len - 4;
    p = section;
    if (parse_section_header(h, &p, p_end) < 0)
        return;
    if (h->tid != SDT_TID)
        return;
    onid = get16(&p, p_end);
    if (onid < 0)
        return;
    val = get8(&p, p_end);
    if (val < 0)
        return;
    for(;;) {
        sid = get16(&p, p_end);
        if (sid < 0)
            break;
        val = get8(&p, p_end);
        if (val < 0)
            break;
        desc_list_len = get16(&p, p_end) & 0xfff;
        if (desc_list_len < 0)
            break;
        desc_list_end = p + desc_list_len;
        if (desc_list_end > p_end)
            break;
        for(;;) {
            desc_tag = get8(&p, desc_list_end);
            if (desc_tag < 0)
                break;
            desc_len = get8(&p, desc_list_end);
            desc_end = p + desc_len;
            if (desc_end > desc_list_end)
                break;
#ifdef DEBUG_SI
            printf("tag: 0x%02x len=%d\n", desc_tag, desc_len);
#endif
            switch(desc_tag) {
            case 0x48:
                service_type = get8(&p, p_end);
                if (service_type < 0)
                    break;
                provider_name = getstr8(&p, p_end);
                if (!provider_name)
                    break;
                name = getstr8(&p, p_end);
                if (!name)
                    break;
                new_service(ts, sid, provider_name, name);
                break;
            default:
                break;
            }
            p = desc_end;
        }
        p = desc_list_end;
    }
    ts->stop_parse = 1;

    /* remove filter */
    mpegts_close_filter(ts, ts->sdt_filter);
    ts->sdt_filter = NULL;
}

/* scan services in a transport stream by looking at the SDT */
void mpegts_scan_sdt(MpegTSContext *ts)
{
    ts->sdt_filter = mpegts_open_section_filter(ts, SDT_PID,
                                                sdt_cb, ts, 1);
}

/* scan services in a transport stream by looking at the PAT (better
   than nothing !) */
void mpegts_scan_pat(MpegTSContext *ts)
{
    ts->pat_filter = mpegts_open_section_filter(ts, PAT_PID,
                                                pat_scan_cb, ts, 1);
}

/* TS stream handling */

enum MpegTSState {
    MPEGTS_HEADER = 0,
    MPEGTS_PESHEADER_FILL,
    MPEGTS_PAYLOAD,
    MPEGTS_SKIP,
};

/* enough for PES header + length */
#define PES_START_SIZE 9
#define MAX_PES_HEADER_SIZE (9 + 255)

struct PESContext {
    int pid;
    int stream_type;
    MpegTSContext *ts;
    AVFormatContext *stream;
    AVStream *st;
    enum MpegTSState state;
    /* used to get the format */
    int data_index;
    int total_size;
    int pes_header_size;
    int64_t pts, dts;
    uint8_t header[MAX_PES_HEADER_SIZE];
};

static int64_t get_pts(const uint8_t *p)
{
    int64_t pts;
    int val;

    pts = (int64_t)((p[0] >> 1) & 0x07) << 30;
    val = (p[1] << 8) | p[2];
    pts |= (int64_t)(val >> 1) << 15;
    val = (p[3] << 8) | p[4];
    pts |= (int64_t)(val >> 1);
    return pts;
}

/* return non zero if a packet could be constructed */
static void mpegts_push_data(void *opaque,
                             const uint8_t *buf, int buf_size, int is_start)
{
    PESContext *pes = opaque;
    MpegTSContext *ts = pes->ts;
    const uint8_t *p;
    int len, code;

    if (is_start) {
        pes->state = MPEGTS_HEADER;
        pes->data_index = 0;
    }
    p = buf;
    while (buf_size > 0) {
        switch(pes->state) {
        case MPEGTS_HEADER:
            len = PES_START_SIZE - pes->data_index;
            if (len > buf_size)
                len = buf_size;
            memcpy(pes->header + pes->data_index, p, len);
            pes->data_index += len;
            p += len;
            buf_size -= len;
            if (pes->data_index == PES_START_SIZE) {
                /* we got all the PES or section header. We can now
                   decide */
#if 0
                av_hex_dump(pes->header, pes->data_index);
#endif
                if (pes->header[0] == 0x00 && pes->header[1] == 0x00 &&
                    pes->header[2] == 0x01) {
                    /* it must be an mpeg2 PES stream */
                    code = pes->header[3] | 0x100;
                    if (!((code >= 0x1c0 && code <= 0x1df) ||
                          (code >= 0x1e0 && code <= 0x1ef) ||
                          (code == 0x1bd)))
                        goto skip;
                    if (!pes->st) {
                        /* allocate stream */
                        new_pes_av_stream(pes, code);
                    }
                    pes->state = MPEGTS_PESHEADER_FILL;
                    pes->total_size = (pes->header[4] << 8) | pes->header[5];
                    /* NOTE: a zero total size means the PES size is
                       unbounded */
                    if (pes->total_size)
                        pes->total_size += 6;
                    pes->pes_header_size = pes->header[8] + 9;
                } else {
                    /* otherwise, it should be a table */
                    /* skip packet */
                skip:
                    pes->state = MPEGTS_SKIP;
                    continue;
                }
            }
            break;
            /**********************************************/
            /* PES packing parsing */
        case MPEGTS_PESHEADER_FILL:
            len = pes->pes_header_size - pes->data_index;
            if (len > buf_size)
                len = buf_size;
            memcpy(pes->header + pes->data_index, p, len);
            pes->data_index += len;
            p += len;
            buf_size -= len;
            if (pes->data_index == pes->pes_header_size) {
                const uint8_t *r;
                unsigned int flags;

                flags = pes->header[7];
                r = pes->header + 9;
                pes->pts = AV_NOPTS_VALUE;
                pes->dts = AV_NOPTS_VALUE;
                if ((flags & 0xc0) == 0x80) {
                    pes->pts = get_pts(r);
                    r += 5;
                } else if ((flags & 0xc0) == 0xc0) {
                    pes->pts = get_pts(r);
                    r += 5;
                    pes->dts = get_pts(r);
                    r += 5;
                }
                /* we got the full header. We parse it and get the payload */
                pes->state = MPEGTS_PAYLOAD;
            }
            break;
        case MPEGTS_PAYLOAD:
            if (pes->total_size) {
                len = pes->total_size - pes->data_index;
                if (len > buf_size)
                    len = buf_size;
            } else {
                len = buf_size;
            }
            if (len > 0) {
                AVPacket *pkt = ts->pkt;
                if (pes->st && av_new_packet(pkt, len) == 0) {
                    memcpy(pkt->data, p, len);
                    pkt->stream_index = pes->st->index;
                    pkt->pts = pes->pts;
                    pkt->dts = pes->dts;
                    /* reset pts values */
                    pes->pts = AV_NOPTS_VALUE;
                    pes->dts = AV_NOPTS_VALUE;
                    ts->stop_parse = 1;
                    return;
                }
            }
            buf_size = 0;
            break;
        case MPEGTS_SKIP:
            buf_size = 0;
            break;
        }
    }
}

static AVStream* new_pes_av_stream(PESContext *pes, uint32_t code)
{
    AVStream *st;
    int codec_type, codec_id;

    switch(pes->stream_type){
    case STREAM_TYPE_AUDIO_MPEG1:
    case STREAM_TYPE_AUDIO_MPEG2:
        codec_type = CODEC_TYPE_AUDIO;
        codec_id = CODEC_ID_MP3;
        break;
    case STREAM_TYPE_VIDEO_MPEG1:
    case STREAM_TYPE_VIDEO_MPEG2:
        codec_type = CODEC_TYPE_VIDEO;
        codec_id = CODEC_ID_MPEG2VIDEO;
        break;
    case STREAM_TYPE_VIDEO_MPEG4:
        codec_type = CODEC_TYPE_VIDEO;
        codec_id = CODEC_ID_MPEG4;
        break;
    case STREAM_TYPE_VIDEO_H264:
        codec_type = CODEC_TYPE_VIDEO;
        codec_id = CODEC_ID_H264;
        break;
    case STREAM_TYPE_AUDIO_AAC:
        codec_type = CODEC_TYPE_AUDIO;
        codec_id = CODEC_ID_AAC;
        break;
    case STREAM_TYPE_AUDIO_AC3:
        codec_type = CODEC_TYPE_AUDIO;
        codec_id = CODEC_ID_AC3;
        break;
    case STREAM_TYPE_AUDIO_DTS:
        codec_type = CODEC_TYPE_AUDIO;
        codec_id = CODEC_ID_DTS;
        break;
    case STREAM_TYPE_SUBTITLE_DVB:
        codec_type = CODEC_TYPE_SUBTITLE;
        codec_id = CODEC_ID_DVB_SUBTITLE;
        break;
    default:
        if (code >= 0x1c0 && code <= 0x1df) {
            codec_type = CODEC_TYPE_AUDIO;
            codec_id = CODEC_ID_MP2;
        } else if (code == 0x1bd) {
            codec_type = CODEC_TYPE_AUDIO;
            codec_id = CODEC_ID_AC3;
        } else {
            codec_type = CODEC_TYPE_VIDEO;
            codec_id = CODEC_ID_MPEG1VIDEO;
        }
        break;
    }
    st = av_new_stream(pes->stream, pes->pid);
    if (st) {
        av_set_pts_info(st, 33, 1, 90000);
        st->priv_data = pes;
        st->codec->codec_type = codec_type;
        st->codec->codec_id = codec_id;
        st->need_parsing = 1;
        pes->st = st;
    }
    return st;
}


static PESContext *add_pes_stream(MpegTSContext *ts, int pid, int stream_type)
{
    MpegTSFilter *tss;
    PESContext *pes;

    /* if no pid found, then add a pid context */
    pes = av_mallocz(sizeof(PESContext));
    if (!pes)
        return 0;
    pes->ts = ts;
    pes->stream = ts->stream;
    pes->pid = pid;
    pes->stream_type = stream_type;
    tss = mpegts_open_pes_filter(ts, pid, mpegts_push_data, pes);
    if (!tss) {
        av_free(pes);
        return 0;
    }
    return pes;
}

/* handle one TS packet */
static void handle_packet(MpegTSContext *ts, const uint8_t *packet)
{
    AVFormatContext *s = ts->stream;
    MpegTSFilter *tss;
    int len, pid, cc, cc_ok, afc, is_start;
    const uint8_t *p, *p_end;

    pid = ((packet[1] & 0x1f) << 8) | packet[2];
    is_start = packet[1] & 0x40;
    tss = ts->pids[pid];
    if (ts->auto_guess && tss == NULL && is_start) {
        add_pes_stream(ts, pid, 0);
        tss = ts->pids[pid];
    }
    if (!tss)
        return;

    /* continuity check (currently not used) */
    cc = (packet[3] & 0xf);
    cc_ok = (tss->last_cc < 0) || ((((tss->last_cc + 1) & 0x0f) == cc));
    tss->last_cc = cc;

    /* skip adaptation field */
    afc = (packet[3] >> 4) & 3;
    p = packet + 4;
    if (afc == 0) /* reserved value */
        return;
    if (afc == 2) /* adaptation field only */
        return;
    if (afc == 3) {
        /* skip adapation field */
        p += p[0] + 1;
    }
    /* if past the end of packet, ignore */
    p_end = packet + TS_PACKET_SIZE;
    if (p >= p_end)
        return;

    if (tss->type == MPEGTS_SECTION) {
        if (is_start) {
            /* pointer field present */
            len = *p++;
            if (p + len > p_end)
                return;
            if (len && cc_ok) {
                /* write remaining section bytes */
                write_section_data(s, tss,
                                   p, len, 0);
                /* check whether filter has been closed */
                if (!ts->pids[pid])
                    return;
            }
            p += len;
            if (p < p_end) {
                write_section_data(s, tss,
                                   p, p_end - p, 1);
            }
        } else {
            if (cc_ok) {
                write_section_data(s, tss,
                                   p, p_end - p, 0);