dv.c

ffmpeg源码分析

            if (fifo_size(&c->audio_data[i], c->audio_data[i].rptr) + data_size >= 100*AVCODEC_MAX_AUDIO_FRAME_SIZE)
                av_log(st->codec, AV_LOG_ERROR, "Can't process DV frame #%d. Insufficient video data or severe sync problem.\n", c->frames);
            fifo_write(&c->audio_data[i], (uint8_t *)data, data_size, &c->audio_data[i].wptr);
        }
    }
out:
    return ((c->has_audio == -1 || c->has_audio == c->n_ast) && c->has_video) ? c->sys->frame_size : 0;
}

DVMuxContext* dv_init_mux(AVFormatContext* s)
{
    DVMuxContext *c;
    AVStream *vst = NULL;
    int i;

    /* we support at most 1 video and 2 audio streams */
    if (s->nb_streams > 3)
        return NULL;

    c = av_mallocz(sizeof(DVMuxContext));
    if (!c)
        return NULL;

    c->n_ast = 0;
    c->ast[0] = c->ast[1] = NULL;

    /* We have to sort out where audio and where video stream is */
    for (i=0; i<s->nb_streams; i++) {
         switch (s->streams[i]->codec->codec_type) {
         case CODEC_TYPE_VIDEO:
               vst = s->streams[i];
               break;
         case CODEC_TYPE_AUDIO:
             c->ast[c->n_ast++] = s->streams[i];
             break;
         default:
               goto bail_out;
         }
    }

    /* Some checks -- DV format is very picky about its incoming streams */
    if (!vst || vst->codec->codec_id != CODEC_ID_DVVIDEO)
        goto bail_out;
    for (i=0; i<c->n_ast; i++) {
        if (c->ast[i] && (c->ast[i]->codec->codec_id != CODEC_ID_PCM_S16LE ||
                          c->ast[i]->codec->sample_rate != 48000 ||
                          c->ast[i]->codec->channels != 2))
            goto bail_out;
    }
    c->sys = dv_codec_profile(vst->codec);
    if (!c->sys)
        goto bail_out;

    if((c->n_ast > 1) && (c->sys->n_difchan < 2)) {
        /* only 1 stereo pair is allowed in 25Mbps mode */
        goto bail_out;
    }

    /* Ok, everything seems to be in working order */
    c->frames = 0;
    c->has_audio = c->n_ast ? 0 : -1;
    c->has_video = 0;
    c->start_time = (time_t)s->timestamp;
    c->aspect = 0; /* 4:3 is the default */
    if ((int)(av_q2d(vst->codec->sample_aspect_ratio) * vst->codec->width / vst->codec->height * 10) == 17) /* 16:9 */
        c->aspect = 0x07;

    for (i=0; i<c->n_ast; i++) {
        if (c->ast[i] && fifo_init(&c->audio_data[i], 100*AVCODEC_MAX_AUDIO_FRAME_SIZE) < 0) {
            while (i>0) {
                i--;
                fifo_free(&c->audio_data[i]);
            }
            goto bail_out;
        }
    }

    dv_format_frame(c, &c->frame_buf[0]);

    return c;

bail_out:
    av_free(c);
    return NULL;
}

void dv_delete_mux(DVMuxContext *c)
{
    int i;
    for (i=0; i < c->n_ast; i++)
        fifo_free(&c->audio_data[i]);
}

DVDemuxContext* dv_init_demux(AVFormatContext *s)
{
    DVDemuxContext *c;

    c = av_mallocz(sizeof(DVDemuxContext));
    if (!c)
        return NULL;

    c->vst = av_new_stream(s, 0);
    if (!c->vst) {
        av_free(c);
        return NULL;
    }

    c->sys = NULL;
    c->fctx = s;
    c->ast[0] = c->ast[1] = NULL;
    c->ach = 0;
    c->frames = 0;
    c->abytes = 0;

    c->vst->codec->codec_type = CODEC_TYPE_VIDEO;
    c->vst->codec->codec_id = CODEC_ID_DVVIDEO;
    c->vst->codec->bit_rate = 25000000;
    c->vst->start_time = 0;

    return c;
}

int dv_get_packet(DVDemuxContext *c, AVPacket *pkt)
{
    int size = -1;
    int i;

    for (i=0; i<c->ach; i++) {
       if (c->ast[i] && c->audio_pkt[i].size) {
           *pkt = c->audio_pkt[i];
           c->audio_pkt[i].size = 0;
           size = pkt->size;
           break;
       }
    }

    return size;
}

int dv_produce_packet(DVDemuxContext *c, AVPacket *pkt,
                      uint8_t* buf, int buf_size)
{
    int size, i;

    if (buf_size < DV_PROFILE_BYTES ||
        !(c->sys = dv_frame_profile(buf)) ||
        buf_size < c->sys->frame_size) {
          return -1;   /* Broken frame, or not enough data */
    }

    /* Queueing audio packet */
    /* FIXME: in case of no audio/bad audio we have to do something */
    size = dv_extract_audio_info(c, buf);
    for (i=0; i<c->ach; i++) {
       c->audio_pkt[i].size = size;
       c->audio_pkt[i].pts  = c->abytes * 30000*8 / c->ast[i]->codec->bit_rate;
    }
    dv_extract_audio(buf, c->audio_buf[0], c->audio_buf[1], c->sys);
    c->abytes += size;

    /* Now it's time to return video packet */
    size = dv_extract_video_info(c, buf);
    av_init_packet(pkt);
    pkt->data     = buf;
    pkt->size     = size;
    pkt->flags   |= PKT_FLAG_KEY;
    pkt->stream_index = c->vst->id;
    pkt->pts      = c->frames;

    c->frames++;

    return size;
}

static int64_t dv_frame_offset(AVFormatContext *s, DVDemuxContext *c,
                              int64_t timestamp, int flags)
{
    // FIXME: sys may be wrong if last dv_read_packet() failed (buffer is junk)
    const DVprofile* sys = dv_codec_profile(c->vst->codec);
    int64_t offset;
    int64_t size = url_fsize(&s->pb);
    int64_t max_offset = ((size-1) / sys->frame_size) * sys->frame_size;

    offset = sys->frame_size * timestamp;

    if (offset > max_offset) offset = max_offset;
    else if (offset < 0) offset = 0;

    return offset;
}

void dv_flush_audio_packets(DVDemuxContext *c)
{
    c->audio_pkt[0].size = c->audio_pkt[1].size = 0;
}

/************************************************************
 * Implementation of the easiest DV storage of all -- raw DV.
 ************************************************************/

typedef struct RawDVContext {
    DVDemuxContext* dv_demux;
    uint8_t         buf[DV_MAX_FRAME_SIZE];
} RawDVContext;

static int dv_read_header(AVFormatContext *s,
                          AVFormatParameters *ap)
{
    RawDVContext *c = s->priv_data;

    c->dv_demux = dv_init_demux(s);
    if (!c->dv_demux)
        return -1;

    if (get_buffer(&s->pb, c->buf, DV_PROFILE_BYTES) <= 0 ||
        url_fseek(&s->pb, -DV_PROFILE_BYTES, SEEK_CUR) < 0)
        return AVERROR_IO;

    c->dv_demux->sys = dv_frame_profile(c->buf);
    s->bit_rate = av_rescale(c->dv_demux->sys->frame_size * 8,
                             c->dv_demux->sys->frame_rate,
                             c->dv_demux->sys->frame_rate_base);

    return 0;
}


static int dv_read_packet(AVFormatContext *s, AVPacket *pkt)
{
    int size;
    RawDVContext *c = s->priv_data;

    size = dv_get_packet(c->dv_demux, pkt);

    if (size < 0) {
        size = c->dv_demux->sys->frame_size;
        if (get_buffer(&s->pb, c->buf, size) <= 0)
            return AVERROR_IO;

        size = dv_produce_packet(c->dv_demux, pkt, c->buf, size);
    }

    return size;
}

static int dv_read_seek(AVFormatContext *s, int stream_index,
                       int64_t timestamp, int flags)
{
    RawDVContext *r = s->priv_data;
    DVDemuxContext *c = r->dv_demux;
    int64_t offset= dv_frame_offset(s, c, timestamp, flags);

    c->frames= offset / c->sys->frame_size;
    if (c->ach)
        c->abytes= av_rescale(c->frames,
                          c->ast[0]->codec->bit_rate * (int64_t)c->sys->frame_rate_base,
                          8*c->sys->frame_rate);

    dv_flush_audio_packets(c);
    return url_fseek(&s->pb, offset, SEEK_SET);
}

static int dv_read_close(AVFormatContext *s)
{
    RawDVContext *c = s->priv_data;
    av_free(c->dv_demux);
    return 0;
}

#ifdef CONFIG_MUXERS
static int dv_write_header(AVFormatContext *s)
{
    s->priv_data = dv_init_mux(s);
    if (!s->priv_data) {
        av_log(s, AV_LOG_ERROR, "Can't initialize DV format!\n"
                    "Make sure that you supply exactly two streams:\n"
                    "     video: 25fps or 29.97fps, audio: 2ch/48Khz/PCM\n"
                    "     (50Mbps allows an optional second audio stream)\n");
        return -1;
    }
    return 0;
}

static int dv_write_packet(struct AVFormatContext *s, AVPacket *pkt)
{
    uint8_t* frame;
    int fsize;

    fsize = dv_assemble_frame((DVMuxContext *)s->priv_data, s->streams[pkt->stream_index],
                              pkt->data, pkt->size, &frame);
    if (fsize > 0) {
        put_buffer(&s->pb, frame, fsize);
        put_flush_packet(&s->pb);
    }
    return 0;
}

/*
 * We might end up with some extra A/V data without matching counterpart.
 * E.g. video data without enough audio to write the complete frame.
 * Currently we simply drop the last frame. I don't know whether this
 * is the best strategy of all
 */
static int dv_write_trailer(struct AVFormatContext *s)
{
    dv_delete_mux((DVMuxContext *)s->priv_data);
    return 0;
}
#endif /* CONFIG_MUXERS */

static AVInputFormat dv_iformat = {
    "dv",
    "DV video format",
    sizeof(RawDVContext),
    NULL,
    dv_read_header,
    dv_read_packet,
    dv_read_close,
    dv_read_seek,
    .extensions = "dv,dif",
};

#ifdef CONFIG_MUXERS
static AVOutputFormat dv_oformat = {
    "dv",
    "DV video format",
    NULL,
    "dv",
    sizeof(DVMuxContext),
    CODEC_ID_PCM_S16LE,
    CODEC_ID_DVVIDEO,
    dv_write_header,
    dv_write_packet,
    dv_write_trailer,
};
#endif

int ff_dv_init(void)
{
    av_register_input_format(&dv_iformat);
#ifdef CONFIG_MUXERS
    av_register_output_format(&dv_oformat);
#endif
    return 0;
}