dv.c

ffmpeg源码分析

    else {
        buf[0] = (fr<<7) | /* FR ID 1 - first half of each channel; 0 - second */
                 (0<<4)  | /* APT (Track application ID) */
                 0x0f;     /* reserved -- always 1 */
    }
    buf[1] = 0xf0 |            /* reserved -- always 1 */
             (syb_num & 0x0f); /* SSYB number 0 - 11   */
    buf[2] = 0xff;             /* reserved -- always 1 */
    return 3;
}

static void dv_format_frame(DVMuxContext *c, uint8_t* buf)
{
    int chan, i, j, k;

    for (chan = 0; chan < c->sys->n_difchan; chan++) {
        for (i = 0; i < c->sys->difseg_size; i++) {
            memset(buf, 0xff, 80 * 6); /* First 6 DIF blocks are for control data */

            /* DV header: 1DIF */
            buf += dv_write_dif_id(dv_sect_header, chan, i, 0, buf);
            buf += dv_write_pack((c->sys->dsf ? dv_header625 : dv_header525), c, buf);
            buf += 72; /* unused bytes */

            /* DV subcode: 2DIFs */
            for (j = 0; j < 2; j++) {
                buf += dv_write_dif_id(dv_sect_subcode, chan, i, j, buf);
                for (k = 0; k < 6; k++) {
                    buf += dv_write_ssyb_id(k, (i < c->sys->difseg_size/2), buf);
                    buf += dv_write_pack(dv_ssyb_packs_dist[i][k], c, buf);
                }
                buf += 29; /* unused bytes */
            }

            /* DV VAUX: 3DIFs */
            for (j = 0; j < 3; j++) {
                buf += dv_write_dif_id(dv_sect_vaux, chan, i, j, buf);
                for (k = 0; k < 15 ; k++)
                    buf += dv_write_pack(dv_vaux_packs_dist[i][k], c, buf);
                buf += 2; /* unused bytes */
            }

            /* DV Audio/Video: 135 Video DIFs + 9 Audio DIFs */
            for (j = 0; j < 135; j++) {
                if (j%15 == 0) {
                    memset(buf, 0xff, 80);
                    buf += dv_write_dif_id(dv_sect_audio, chan, i, j/15, buf);
                    buf += 77; /* audio control & shuffled PCM audio */
                }
                buf += dv_write_dif_id(dv_sect_video, chan, i, j, buf);
                buf += 77; /* 1 video macro block: 1 bytes control
                              4 * 14 bytes Y 8x8 data
                              10 bytes Cr 8x8 data
                              10 bytes Cb 8x8 data */
            }
        }
    }
}

static void dv_inject_audio(DVMuxContext *c, const uint8_t* pcm, int channel, uint8_t* frame_ptr)
{
    int i, j, d, of, size;
    size = 4 * dv_audio_frame_size(c->sys, c->frames);
    frame_ptr += channel * c->sys->difseg_size * 150 * 80;
    for (i = 0; i < c->sys->difseg_size; i++) {
       frame_ptr += 6 * 80; /* skip DIF segment header */
       for (j = 0; j < 9; j++) {
          dv_write_pack(dv_aaux_packs_dist[i][j], c, &frame_ptr[3]);
          for (d = 8; d < 80; d+=2) {
             of = c->sys->audio_shuffle[i][j] + (d - 8)/2 * c->sys->audio_stride;
             if (of*2 >= size)
                 continue;

             frame_ptr[d] = pcm[of*2+1]; // FIXME: may be we have to admit
             frame_ptr[d+1] = pcm[of*2]; //        that DV is a big endian PCM
          }
          frame_ptr += 16 * 80; /* 15 Video DIFs + 1 Audio DIF */
       }
    }
}

static void dv_inject_video(DVMuxContext *c, const uint8_t* video_data, uint8_t* frame_ptr)
{
    int chan, i, j;
    int ptr = 0;

    for (chan = 0; chan < c->sys->n_difchan; chan++) {
        for (i = 0; i < c->sys->difseg_size; i++) {
            ptr += 6 * 80; /* skip DIF segment header */
            for (j = 0; j < 135; j++) {
                if (j%15 == 0)
                    ptr += 80; /* skip Audio DIF */
                ptr += 3;
                memcpy(frame_ptr + ptr, video_data + ptr, 77);
                ptr += 77;
            }
        }
    }
}

/*
 * This is the dumbest implementation of all -- it simply looks at
 * a fixed offset and if pack isn't there -- fails. We might want
 * to have a fallback mechanism for complete search of missing packs.
 */
static const uint8_t* dv_extract_pack(uint8_t* frame, enum dv_pack_type t)
{
    int offs;

    switch (t) {
    case dv_audio_source:
          offs = (80*6 + 80*16*3 + 3);
          break;
    case dv_audio_control:
          offs = (80*6 + 80*16*4 + 3);
          break;
    case dv_video_control:
          offs = (80*5 + 48 + 5);
          break;
    default:
          return NULL;
    }

    return (frame[offs] == t ? &frame[offs] : NULL);
}

/*
 * There's a couple of assumptions being made here:
 * 1. By default we silence erroneous (0x8000/16bit 0x800/12bit) audio samples.
 *    We can pass them upwards when ffmpeg will be ready to deal with them.
 * 2. We don't do software emphasis.
 * 3. Audio is always returned as 16bit linear samples: 12bit nonlinear samples
 *    are converted into 16bit linear ones.
 */
static int dv_extract_audio(uint8_t* frame, uint8_t* pcm, uint8_t* pcm2,
                            const DVprofile *sys)
{
    int size, chan, i, j, d, of, smpls, freq, quant, half_ch;
    uint16_t lc, rc;
    const uint8_t* as_pack;

    as_pack = dv_extract_pack(frame, dv_audio_source);
    if (!as_pack)    /* No audio ? */
        return 0;

    smpls = as_pack[1] & 0x3f; /* samples in this frame - min. samples */
    freq = (as_pack[4] >> 3) & 0x07; /* 0 - 48KHz, 1 - 44,1kHz, 2 - 32 kHz */
    quant = as_pack[4] & 0x07; /* 0 - 16bit linear, 1 - 12bit nonlinear */

    if (quant > 1)
        return -1; /* Unsupported quantization */

    size = (sys->audio_min_samples[freq] + smpls) * 4; /* 2ch, 2bytes */
    half_ch = sys->difseg_size/2;

    /* for each DIF channel */
    for (chan = 0; chan < sys->n_difchan; chan++) {
        /* for each DIF segment */
        for (i = 0; i < sys->difseg_size; i++) {
            frame += 6 * 80; /* skip DIF segment header */
            if (quant == 1 && i == half_ch) {
                /* next stereo channel (12bit mode only) */
                if (!pcm2)
                    break;
                else
                    pcm = pcm2;
            }

            /* for each AV sequence */
            for (j = 0; j < 9; j++) {
                for (d = 8; d < 80; d += 2) {
                    if (quant == 0) {  /* 16bit quantization */
                        of = sys->audio_shuffle[i][j] + (d - 8)/2 * sys->audio_stride;
                        if (of*2 >= size)
                            continue;

                        pcm[of*2] = frame[d+1]; // FIXME: may be we have to admit
                        pcm[of*2+1] = frame[d]; //        that DV is a big endian PCM
                        if (pcm[of*2+1] == 0x80 && pcm[of*2] == 0x00)
                            pcm[of*2+1] = 0;
                    } else {           /* 12bit quantization */
                        lc = ((uint16_t)frame[d] << 4) |
                             ((uint16_t)frame[d+2] >> 4);
                        rc = ((uint16_t)frame[d+1] << 4) |
                             ((uint16_t)frame[d+2] & 0x0f);
                        lc = (lc == 0x800 ? 0 : dv_audio_12to16(lc));
                        rc = (rc == 0x800 ? 0 : dv_audio_12to16(rc));

                        of = sys->audio_shuffle[i%half_ch][j] + (d - 8)/3 * sys->audio_stride;
                        if (of*2 >= size)
                            continue;

                        pcm[of*2] = lc & 0xff; // FIXME: may be we have to admit
                        pcm[of*2+1] = lc >> 8; //        that DV is a big endian PCM
                        of = sys->audio_shuffle[i%half_ch+half_ch][j] +
                            (d - 8)/3 * sys->audio_stride;
                        pcm[of*2] = rc & 0xff; // FIXME: may be we have to admit
                        pcm[of*2+1] = rc >> 8; //        that DV is a big endian PCM
                        ++d;
                    }
                }

                frame += 16 * 80; /* 15 Video DIFs + 1 Audio DIF */
            }
        }

        /* next stereo channel (50Mbps only) */
        if(!pcm2)
            break;
        pcm = pcm2;
    }

    return size;
}

static int dv_extract_audio_info(DVDemuxContext* c, uint8_t* frame)
{
    const uint8_t* as_pack;
    int freq, stype, smpls, quant, i, ach;

    as_pack = dv_extract_pack(frame, dv_audio_source);
    if (!as_pack || !c->sys) {    /* No audio ? */
        c->ach = 0;
        return 0;
    }

    smpls = as_pack[1] & 0x3f; /* samples in this frame - min. samples */
    freq = (as_pack[4] >> 3) & 0x07; /* 0 - 48KHz, 1 - 44,1kHz, 2 - 32 kHz */
    stype = (as_pack[3] & 0x1f); /* 0 - 2CH, 2 - 4CH */
    quant = as_pack[4] & 0x07; /* 0 - 16bit linear, 1 - 12bit nonlinear */

    /* note: ach counts PAIRS of channels (i.e. stereo channels) */
    ach = (stype == 2 || (quant && (freq == 2))) ? 2 : 1;

    /* Dynamic handling of the audio streams in DV */
    for (i=0; i<ach; i++) {
       if (!c->ast[i]) {
           c->ast[i] = av_new_stream(c->fctx, 0);
           if (!c->ast[i])
               break;
           av_set_pts_info(c->ast[i], 64, 1, 30000);
           c->ast[i]->codec->codec_type = CODEC_TYPE_AUDIO;
           c->ast[i]->codec->codec_id = CODEC_ID_PCM_S16LE;

           av_init_packet(&c->audio_pkt[i]);
           c->audio_pkt[i].size     = 0;
           c->audio_pkt[i].data     = c->audio_buf[i];
           c->audio_pkt[i].stream_index = c->ast[i]->index;
           c->audio_pkt[i].flags |= PKT_FLAG_KEY;
       }
       c->ast[i]->codec->sample_rate = dv_audio_frequency[freq];
       c->ast[i]->codec->channels = 2;
       c->ast[i]->codec->bit_rate = 2 * dv_audio_frequency[freq] * 16;
       c->ast[i]->start_time = 0;
    }
    c->ach = i;

    return (c->sys->audio_min_samples[freq] + smpls) * 4; /* 2ch, 2bytes */;
}

static int dv_extract_video_info(DVDemuxContext *c, uint8_t* frame)
{
    const uint8_t* vsc_pack;
    AVCodecContext* avctx;
    int apt, is16_9;
    int size = 0;

    if (c->sys) {
        avctx = c->vst->codec;

        av_set_pts_info(c->vst, 64, c->sys->frame_rate_base, c->sys->frame_rate);
        avctx->time_base= (AVRational){c->sys->frame_rate_base, c->sys->frame_rate};
        if(!avctx->width){
            avctx->width = c->sys->width;
            avctx->height = c->sys->height;
        }
        avctx->pix_fmt = c->sys->pix_fmt;

        /* finding out SAR is a little bit messy */
        vsc_pack = dv_extract_pack(frame, dv_video_control);
        apt = frame[4] & 0x07;
        is16_9 = (vsc_pack && ((vsc_pack[2] & 0x07) == 0x02 ||
                               (!apt && (vsc_pack[2] & 0x07) == 0x07)));
        avctx->sample_aspect_ratio = c->sys->sar[is16_9];
        avctx->bit_rate = av_rescale(c->sys->frame_size * 8,
                                     c->sys->frame_rate,
                                     c->sys->frame_rate_base);
        size = c->sys->frame_size;
    }
    return size;
}

/*
 * The following 6 functions constitute our interface to the world
 */

int dv_assemble_frame(DVMuxContext *c, AVStream* st,
                      const uint8_t* data, int data_size, uint8_t** frame)
{
    uint8_t pcm[8192];
    int i;

    *frame = &c->frame_buf[0];
    if (c->has_audio && c->has_video &&
        (c->has_audio == -1 || c->has_audio == c->n_ast)) {
        /* must be a stale frame */
        dv_format_frame(c, *frame);
        c->frames++;
        if (c->has_audio > 0)
            c->has_audio = 0;
        c->has_video = 0;
    }

    if (st->codec->codec_type == CODEC_TYPE_VIDEO) {
        /* FIXME: we have to have more sensible approach than this one */
        if (c->has_video)
            av_log(st->codec, AV_LOG_ERROR, "Can't process DV frame #%d. Insufficient audio data or severe sync problem.\n", c->frames);

        dv_inject_video(c, data, *frame);
        c->has_video = 1;
        data_size = 0;
        if (c->has_audio < 0)
            goto out;
    }

    for (i = 0; i < c->n_ast; i++) {
        int reqasize, fsize;
        if (st != c->ast[i])
            continue;
        reqasize = 4 * dv_audio_frame_size(c->sys, c->frames);
        fsize = fifo_size(&c->audio_data[i], c->audio_data[i].rptr);
        if (st->codec->codec_type == CODEC_TYPE_AUDIO ||
            (c->has_video && fsize >= reqasize)) {
            if (fsize + data_size >= reqasize && (c->has_audio < c->n_ast)) {
                if (fsize >= reqasize) {
                    fifo_read(&c->audio_data[i], &pcm[0], reqasize, &c->audio_data[i].rptr);
                } else {
                    fifo_read(&c->audio_data[i], &pcm[0], fsize, &c->audio_data[i].rptr);
                    memcpy(&pcm[fsize], &data[0], reqasize - fsize);
                    data += reqasize - fsize;
                    data_size -= reqasize - fsize;
                }
                dv_inject_audio(c, &pcm[0], i, *frame);
                c->has_audio += 1;
            }
            /* FIXME: we have to have more sensible approach than this one */