mpegtsenc.c

ffmpeg的完整源代码和作者自己写的文档。不但有在Linux的工程哦

    dynarray_add(&ts->services, &ts->nb_services, service);
    return service;
}

static void section_write_packet(MpegTSSection *s, const uint8_t *packet)
{
    AVFormatContext *ctx = s->opaque;
    put_buffer(&ctx->pb, packet, TS_PACKET_SIZE);
}

static int mpegts_write_header(AVFormatContext *s)
{
    MpegTSWrite *ts = s->priv_data;
    MpegTSWriteStream *ts_st;
    MpegTSService *service;
    AVStream *st;
    int i, total_bit_rate;
    const char *service_name;

    ts->tsid = DEFAULT_TSID;
    ts->onid = DEFAULT_ONID;
    /* allocate a single DVB service */
    service_name = s->title;
    if (service_name[0] == '\0')
        service_name = DEFAULT_SERVICE_NAME;
    service = mpegts_add_service(ts, DEFAULT_SID,
                                 DEFAULT_PROVIDER_NAME, service_name);
    service->pmt.write_packet = section_write_packet;
    service->pmt.opaque = s;

    ts->pat.pid = PAT_PID;
    ts->pat.cc = 0;
    ts->pat.write_packet = section_write_packet;
    ts->pat.opaque = s;

    ts->sdt.pid = SDT_PID;
    ts->sdt.cc = 0;
    ts->sdt.write_packet = section_write_packet;
    ts->sdt.opaque = s;

    /* assign pids to each stream */
    total_bit_rate = 0;
    for(i = 0;i < s->nb_streams; i++) {
        st = s->streams[i];
        ts_st = av_mallocz(sizeof(MpegTSWriteStream));
        if (!ts_st)
            goto fail;
        st->priv_data = ts_st;
        ts_st->service = service;
        ts_st->pid = DEFAULT_START_PID + i;
        ts_st->payload_pts = AV_NOPTS_VALUE;
        ts_st->payload_dts = AV_NOPTS_VALUE;
        /* update PCR pid by using the first video stream */
        if (st->codec->codec_type == CODEC_TYPE_VIDEO &&
            service->pcr_pid == 0x1fff)
            service->pcr_pid = ts_st->pid;
        total_bit_rate += st->codec->bit_rate;
    }

    /* if no video stream, use the first stream as PCR */
    if (service->pcr_pid == 0x1fff && s->nb_streams > 0) {
        ts_st = s->streams[0]->priv_data;
        service->pcr_pid = ts_st->pid;
    }

    if (total_bit_rate <= 8 * 1024)
        total_bit_rate = 8 * 1024;
    service->pcr_packet_freq = (total_bit_rate * PCR_RETRANS_TIME) /
        (TS_PACKET_SIZE * 8 * 1000);
    ts->sdt_packet_freq = (total_bit_rate * SDT_RETRANS_TIME) /
        (TS_PACKET_SIZE * 8 * 1000);
    ts->pat_packet_freq = (total_bit_rate * PAT_RETRANS_TIME) /
        (TS_PACKET_SIZE * 8 * 1000);
#if 0
    printf("%d %d %d\n",
           total_bit_rate, ts->sdt_packet_freq, ts->pat_packet_freq);
#endif

    /* write info at the start of the file, so that it will be fast to
       find them */
    mpegts_write_sdt(s);
    mpegts_write_pat(s);
    for(i = 0; i < ts->nb_services; i++) {
        mpegts_write_pmt(s, ts->services[i]);
    }
    put_flush_packet(&s->pb);

    return 0;

 fail:
    for(i = 0;i < s->nb_streams; i++) {
        st = s->streams[i];
        av_free(st->priv_data);
    }
    return -1;
}

/* send SDT, PAT and PMT tables regulary */
static void retransmit_si_info(AVFormatContext *s)
{
    MpegTSWrite *ts = s->priv_data;
    int i;

    if (++ts->sdt_packet_count == ts->sdt_packet_freq) {
        ts->sdt_packet_count = 0;
        mpegts_write_sdt(s);
    }
    if (++ts->pat_packet_count == ts->pat_packet_freq) {
        ts->pat_packet_count = 0;
        mpegts_write_pat(s);
        for(i = 0; i < ts->nb_services; i++) {
            mpegts_write_pmt(s, ts->services[i]);
        }
    }
}

static void write_pts(uint8_t *q, int fourbits, int64_t pts)
{
    int val;

    val = fourbits << 4 | (((pts >> 30) & 0x07) << 1) | 1;
    *q++ = val;
    val = (((pts >> 15) & 0x7fff) << 1) | 1;
    *q++ = val >> 8;
    *q++ = val;
    val = (((pts) & 0x7fff) << 1) | 1;
    *q++ = val >> 8;
    *q++ = val;
}

/* NOTE: pes_data contains all the PES packet */
static void mpegts_write_pes(AVFormatContext *s, AVStream *st,
                             const uint8_t *payload, int payload_size,
                             int64_t pts, int64_t dts)
{
    MpegTSWriteStream *ts_st = st->priv_data;
    uint8_t buf[TS_PACKET_SIZE];
    uint8_t *q;
    int val, is_start, len, header_len, write_pcr, private_code, flags;
    int afc_len, stuffing_len;
    int64_t pcr = -1; /* avoid warning */

    is_start = 1;
    while (payload_size > 0) {
        retransmit_si_info(s);

        write_pcr = 0;
        if (ts_st->pid == ts_st->service->pcr_pid) {
            ts_st->service->pcr_packet_count++;
            if (ts_st->service->pcr_packet_count >=
                ts_st->service->pcr_packet_freq) {
                ts_st->service->pcr_packet_count = 0;
                write_pcr = 1;
                /* XXX: this is incorrect, but at least we have a PCR
                   value */
                pcr = pts;
            }
        }

        /* prepare packet header */
        q = buf;
        *q++ = 0x47;
        val = (ts_st->pid >> 8);
        if (is_start)
            val |= 0x40;
        *q++ = val;
        *q++ = ts_st->pid;
        *q++ = 0x10 | ts_st->cc | (write_pcr ? 0x20 : 0);
        ts_st->cc = (ts_st->cc + 1) & 0xf;
        if (write_pcr) {
            *q++ = 7; /* AFC length */
            *q++ = 0x10; /* flags: PCR present */
            *q++ = pcr >> 25;
            *q++ = pcr >> 17;
            *q++ = pcr >> 9;
            *q++ = pcr >> 1;
            *q++ = (pcr & 1) << 7;
            *q++ = 0;
        }
        if (is_start) {
            /* write PES header */
            *q++ = 0x00;
            *q++ = 0x00;
            *q++ = 0x01;
            private_code = 0;
            if (st->codec->codec_type == CODEC_TYPE_VIDEO) {
                *q++ = 0xe0;
            } else if (st->codec->codec_type == CODEC_TYPE_AUDIO &&
                       (st->codec->codec_id == CODEC_ID_MP2 ||
                        st->codec->codec_id == CODEC_ID_MP3)) {
                *q++ = 0xc0;
            } else {
                *q++ = 0xbd;
                if (st->codec->codec_type == CODEC_TYPE_SUBTITLE) {
                    private_code = 0x20;
                }
            }
            header_len = 0;
            flags = 0;
            if (pts != AV_NOPTS_VALUE) {
                header_len += 5;
                flags |= 0x80;
            }
            if (dts != AV_NOPTS_VALUE) {
                header_len += 5;
                flags |= 0x40;
            }
            len = payload_size + header_len + 3;
            if (private_code != 0)
                len++;
            *q++ = len >> 8;
            *q++ = len;
            val = 0x80;
            /* data alignment indicator is required for subtitle data */
            if (st->codec->codec_type == CODEC_TYPE_SUBTITLE)
                val |= 0x04;
            *q++ = val;
            *q++ = flags;
            *q++ = header_len;
            if (pts != AV_NOPTS_VALUE) {
                write_pts(q, flags >> 6, pts);
                q += 5;
            }
            if (dts != AV_NOPTS_VALUE) {
                write_pts(q, 1, dts);
                q += 5;
            }
            if (private_code != 0)
                *q++ = private_code;
            is_start = 0;
        }
        /* header size */
        header_len = q - buf;
        /* data len */
        len = TS_PACKET_SIZE - header_len;
        if (len > payload_size)
            len = payload_size;
        stuffing_len = TS_PACKET_SIZE - header_len - len;
        if (stuffing_len > 0) {
            /* add stuffing with AFC */
            if (buf[3] & 0x20) {
                /* stuffing already present: increase its size */
                afc_len = buf[4] + 1;
                memmove(buf + 4 + afc_len + stuffing_len,
                        buf + 4 + afc_len,
                        header_len - (4 + afc_len));
                buf[4] += stuffing_len;
                memset(buf + 4 + afc_len, 0xff, stuffing_len);
            } else {
                /* add stuffing */
                memmove(buf + 4 + stuffing_len, buf + 4, header_len - 4);
                buf[3] |= 0x20;
                buf[4] = stuffing_len - 1;
                if (stuffing_len >= 2) {
                    buf[5] = 0x00;
                    memset(buf + 6, 0xff, stuffing_len - 2);
                }
            }
        }
        memcpy(buf + TS_PACKET_SIZE - len, payload, len);
        payload += len;
        payload_size -= len;
        put_buffer(&s->pb, buf, TS_PACKET_SIZE);
    }
    put_flush_packet(&s->pb);
}

static int mpegts_write_packet(AVFormatContext *s, AVPacket *pkt)
{
    AVStream *st = s->streams[pkt->stream_index];
    int size= pkt->size;
    uint8_t *buf= pkt->data;
    MpegTSWriteStream *ts_st = st->priv_data;
    int len, max_payload_size;

    if (st->codec->codec_type == CODEC_TYPE_SUBTITLE) {
        /* for subtitle, a single PES packet must be generated */
        mpegts_write_pes(s, st, buf, size, pkt->pts, AV_NOPTS_VALUE);
        return 0;
    }

    max_payload_size = DEFAULT_PES_PAYLOAD_SIZE;
    while (size > 0) {
        len = max_payload_size - ts_st->payload_index;
        if (len > size)
            len = size;
        memcpy(ts_st->payload + ts_st->payload_index, buf, len);
        buf += len;
        size -= len;
        ts_st->payload_index += len;
        if (ts_st->payload_pts == AV_NOPTS_VALUE)
            ts_st->payload_pts = pkt->pts;
        if (ts_st->payload_dts == AV_NOPTS_VALUE)
            ts_st->payload_dts = pkt->dts;
        if (ts_st->payload_index >= max_payload_size) {
            mpegts_write_pes(s, st, ts_st->payload, ts_st->payload_index,
                             ts_st->payload_pts, ts_st->payload_dts);
            ts_st->payload_pts = AV_NOPTS_VALUE;
            ts_st->payload_dts = AV_NOPTS_VALUE;
            ts_st->payload_index = 0;
        }
    }
    return 0;
}

static int mpegts_write_end(AVFormatContext *s)
{
    MpegTSWrite *ts = s->priv_data;
    MpegTSWriteStream *ts_st;
    MpegTSService *service;
    AVStream *st;
    int i;

    /* flush current packets */
    for(i = 0; i < s->nb_streams; i++) {
        st = s->streams[i];
        ts_st = st->priv_data;
        if (ts_st->payload_index > 0) {
            mpegts_write_pes(s, st, ts_st->payload, ts_st->payload_index,
                             ts_st->payload_pts, ts_st->payload_dts);
        }
    }
    put_flush_packet(&s->pb);

    for(i = 0; i < ts->nb_services; i++) {
        service = ts->services[i];
        av_freep(&service->provider_name);
        av_freep(&service->name);
        av_free(service);
    }
    av_free(ts->services);

    return 0;
}

AVOutputFormat mpegts_muxer = {
    "mpegts",
    "MPEG2 transport stream format",
    "video/x-mpegts",
    "ts",
    sizeof(MpegTSWrite),
    CODEC_ID_MP2,
    CODEC_ID_MPEG2VIDEO,
    mpegts_write_header,
    mpegts_write_packet,
    mpegts_write_end,
};