nsvdec.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

    //url_fseek(pb, size, SEEK_SET); /* go back to end of header */
#undef V
#endif

    url_fseek(pb, nsv->base_offset + size, SEEK_SET); /* required for dumbdriving-271.nsv (2 extra bytes) */

    if (url_feof(pb))
        return -1;
    nsv->state = NSV_HAS_READ_NSVF;
    return 0;
}

static int nsv_parse_NSVs_header(AVFormatContext *s, AVFormatParameters *ap)
{
    NSVContext *nsv = s->priv_data;
    ByteIOContext *pb = &s->pb;
    uint32_t vtag, atag;
    uint16_t vwidth, vheight;
    AVRational framerate;
    int i;
    AVStream *st;
    NSVStream *nst;
    PRINT(("%s()\n", __FUNCTION__));

    vtag = get_le32(pb);
    atag = get_le32(pb);
    vwidth = get_le16(pb);
    vheight = get_le16(pb);
    i = get_byte(pb);

    PRINT(("NSV NSVs framerate code %2x\n", i));
    if(i&0x80) { /* odd way of giving native framerates from docs */
        int t=(i & 0x7F)>>2;
        if(t<16) framerate = (AVRational){1, t+1};
        else     framerate = (AVRational){t-15, 1};

        if(i&1){
            framerate.num *= 1000;
            framerate.den *= 1001;
        }

        if((i&3)==3)      framerate.num *= 24;
        else if((i&3)==2) framerate.num *= 25;
        else              framerate.num *= 30;
    }
    else
        framerate= (AVRational){i, 1};

    nsv->avsync = get_le16(pb);
#ifdef DEBUG
    print_tag("NSV NSVs vtag", vtag, 0);
    print_tag("NSV NSVs atag", atag, 0);
    PRINT(("NSV NSVs vsize %dx%d\n", vwidth, vheight));
#endif

    /* XXX change to ap != NULL ? */
    if (s->nb_streams == 0) { /* streams not yet published, let's do that */
        nsv->vtag = vtag;
        nsv->atag = atag;
        nsv->vwidth = vwidth;
        nsv->vheight = vwidth;
        if (vtag != T_NONE) {
            st = av_new_stream(s, NSV_ST_VIDEO);
            if (!st)
                goto fail;

            nst = av_mallocz(sizeof(NSVStream));
            if (!nst)
                goto fail;
            st->priv_data = nst;
            st->codec->codec_type = CODEC_TYPE_VIDEO;
            st->codec->codec_tag = vtag;
            st->codec->codec_id = codec_get_id(nsv_codec_video_tags, vtag);
            st->codec->width = vwidth;
            st->codec->height = vheight;
            st->codec->bits_per_sample = 24; /* depth XXX */

            av_set_pts_info(st, 64, framerate.den, framerate.num);
            st->start_time = 0;
            st->duration = av_rescale(nsv->duration, framerate.num, 1000*framerate.den);
        }
        if (atag != T_NONE) {
#ifndef DISABLE_AUDIO
            st = av_new_stream(s, NSV_ST_AUDIO);
            if (!st)
                goto fail;

            nst = av_mallocz(sizeof(NSVStream));
            if (!nst)
                goto fail;
            st->priv_data = nst;
            st->codec->codec_type = CODEC_TYPE_AUDIO;
            st->codec->codec_tag = atag;
            st->codec->codec_id = codec_get_id(nsv_codec_audio_tags, atag);

            st->need_parsing = AVSTREAM_PARSE_FULL; /* for PCM we will read a chunk later and put correct info */

            /* set timebase to common denominator of ms and framerate */
            av_set_pts_info(st, 64, 1, framerate.num*1000);
            st->start_time = 0;
            st->duration = (int64_t)nsv->duration * framerate.num;
#endif
        }
#ifdef CHECK_SUBSEQUENT_NSVS
    } else {
        if (nsv->vtag != vtag || nsv->atag != atag || nsv->vwidth != vwidth || nsv->vheight != vwidth) {
            PRINT(("NSV NSVs header values differ from the first one!!!\n"));
            //return -1;
        }
#endif /* CHECK_SUBSEQUENT_NSVS */
    }

    nsv->state = NSV_HAS_READ_NSVS;
    return 0;
fail:
    /* XXX */
    nsv->state = NSV_UNSYNC;
    return -1;
}

static int nsv_read_header(AVFormatContext *s, AVFormatParameters *ap)
{
    NSVContext *nsv = s->priv_data;
    int i, err;

    PRINT(("%s()\n", __FUNCTION__));
    PRINT(("filename '%s'\n", s->filename));

    nsv->state = NSV_UNSYNC;
    nsv->ahead[0].data = nsv->ahead[1].data = NULL;

    for (i = 0; i < NSV_MAX_RESYNC_TRIES; i++) {
        if (nsv_resync(s) < 0)
            return -1;
        if (nsv->state == NSV_FOUND_NSVF)
            err = nsv_parse_NSVf_header(s, ap);
            /* we need the first NSVs also... */
        if (nsv->state == NSV_FOUND_NSVS) {
            err = nsv_parse_NSVs_header(s, ap);
            break; /* we just want the first one */
        }
    }
    if (s->nb_streams < 1) /* no luck so far */
        return -1;
    /* now read the first chunk, so we can attempt to decode more info */
    err = nsv_read_chunk(s, 1);

    PRINT(("parsed header\n"));
    return 0;
}

static int nsv_read_chunk(AVFormatContext *s, int fill_header)
{
    NSVContext *nsv = s->priv_data;
    ByteIOContext *pb = &s->pb;
    AVStream *st[2] = {NULL, NULL};
    NSVStream *nst;
    AVPacket *pkt;
    int i, err = 0;
    uint8_t auxcount; /* number of aux metadata, also 4 bits of vsize */
    uint32_t vsize;
    uint16_t asize;
    uint16_t auxsize;
    uint32_t auxtag;

    PRINT(("%s(%d)\n", __FUNCTION__, fill_header));

    if (nsv->ahead[0].data || nsv->ahead[1].data)
        return 0; //-1; /* hey! eat what you've in your plate first! */

null_chunk_retry:
    if (url_feof(pb))
        return -1;

    for (i = 0; i < NSV_MAX_RESYNC_TRIES && nsv->state < NSV_FOUND_NSVS && !err; i++)
        err = nsv_resync(s);
    if (err < 0)
        return err;
    if (nsv->state == NSV_FOUND_NSVS)
        err = nsv_parse_NSVs_header(s, NULL);
    if (err < 0)
        return err;
    if (nsv->state != NSV_HAS_READ_NSVS && nsv->state != NSV_FOUND_BEEF)
        return -1;

    auxcount = get_byte(pb);
    vsize = get_le16(pb);
    asize = get_le16(pb);
    vsize = (vsize << 4) | (auxcount >> 4);
    auxcount &= 0x0f;
    PRINT(("NSV CHUNK %d aux, %u bytes video, %d bytes audio\n", auxcount, vsize, asize));
    /* skip aux stuff */
    for (i = 0; i < auxcount; i++) {
        auxsize = get_le16(pb);
        auxtag = get_le32(pb);
        PRINT(("NSV aux data: '%c%c%c%c', %d bytes\n",
              (auxtag & 0x0ff),
              ((auxtag >> 8) & 0x0ff),
              ((auxtag >> 16) & 0x0ff),
              ((auxtag >> 24) & 0x0ff),
              auxsize));
        url_fskip(pb, auxsize);
        vsize -= auxsize + sizeof(uint16_t) + sizeof(uint32_t); /* that's becoming braindead */
    }

    if (url_feof(pb))
        return -1;
    if (!vsize && !asize) {
        nsv->state = NSV_UNSYNC;
        goto null_chunk_retry;
    }

    /* map back streams to v,a */
    if (s->streams[0])
        st[s->streams[0]->id] = s->streams[0];
    if (s->streams[1])
        st[s->streams[1]->id] = s->streams[1];

    if (vsize/* && st[NSV_ST_VIDEO]*/) {
        nst = st[NSV_ST_VIDEO]->priv_data;
        pkt = &nsv->ahead[NSV_ST_VIDEO];
        av_get_packet(pb, pkt, vsize);
        pkt->stream_index = st[NSV_ST_VIDEO]->index;//NSV_ST_VIDEO;
        pkt->dts = nst->frame_offset;
        pkt->flags |= nsv->state == NSV_HAS_READ_NSVS ? PKT_FLAG_KEY : 0; /* keyframe only likely on a sync frame */
/*
        for (i = 0; i < MIN(8, vsize); i++)
            PRINT(("NSV video: [%d] = %02x\n", i, pkt->data[i]));
*/
    }
    if(st[NSV_ST_VIDEO])
        ((NSVStream*)st[NSV_ST_VIDEO]->priv_data)->frame_offset++;

    if (asize/*st[NSV_ST_AUDIO]*/) {
        nst = st[NSV_ST_AUDIO]->priv_data;
        pkt = &nsv->ahead[NSV_ST_AUDIO];
        /* read raw audio specific header on the first audio chunk... */
        /* on ALL audio chunks ?? seems so! */
        if (asize && st[NSV_ST_AUDIO]->codec->codec_tag == MKTAG('P', 'C', 'M', ' ')/* && fill_header*/) {
            uint8_t bps;
            uint8_t channels;
            uint16_t samplerate;
            bps = get_byte(pb);
            channels = get_byte(pb);
            samplerate = get_le16(pb);
            asize-=4;
            PRINT(("NSV RAWAUDIO: bps %d, nchan %d, srate %d\n", bps, channels, samplerate));
            if (fill_header) {
                st[NSV_ST_AUDIO]->need_parsing = AVSTREAM_PARSE_NONE; /* we know everything */
                if (bps != 16) {
                    PRINT(("NSV AUDIO bit/sample != 16 (%d)!!!\n", bps));
                }
                bps /= channels; // ???
                if (bps == 8)
                    st[NSV_ST_AUDIO]->codec->codec_id = CODEC_ID_PCM_U8;
                samplerate /= 4;/* UGH ??? XXX */
                channels = 1;
                st[NSV_ST_AUDIO]->codec->channels = channels;
                st[NSV_ST_AUDIO]->codec->sample_rate = samplerate;
                PRINT(("NSV RAWAUDIO: bps %d, nchan %d, srate %d\n", bps, channels, samplerate));
            }
        }
        av_get_packet(pb, pkt, asize);
        pkt->stream_index = st[NSV_ST_AUDIO]->index;//NSV_ST_AUDIO;
        pkt->flags |= nsv->state == NSV_HAS_READ_NSVS ? PKT_FLAG_KEY : 0; /* keyframe only likely on a sync frame */
        if( nsv->state == NSV_HAS_READ_NSVS && st[NSV_ST_VIDEO] ) {
            /* on a nsvs frame we have new information on a/v sync */
            pkt->dts = (((NSVStream*)st[NSV_ST_VIDEO]->priv_data)->frame_offset-1);
            pkt->dts *= (int64_t)1000 * st[NSV_ST_VIDEO]->time_base.num;
            pkt->dts += (int64_t)nsv->avsync * st[NSV_ST_VIDEO]->time_base.den;
            PRINT(("NSV AUDIO: sync:%d, dts:%"PRId64, nsv->avsync, pkt->dts));
        }
        nst->frame_offset++;
    }

    nsv->state = NSV_UNSYNC;
    return 0;
}


static int nsv_read_packet(AVFormatContext *s, AVPacket *pkt)
{
    NSVContext *nsv = s->priv_data;
    int i, err = 0;

    PRINT(("%s()\n", __FUNCTION__));

    /* in case we don't already have something to eat ... */
    if (nsv->ahead[0].data == NULL && nsv->ahead[1].data == NULL)
        err = nsv_read_chunk(s, 0);
    if (err < 0)
        return err;

    /* now pick one of the plates */
    for (i = 0; i < 2; i++) {
        if (nsv->ahead[i].data) {
                PRINT(("%s: using cached packet[%d]\n", __FUNCTION__, i));
            /* avoid the cost of new_packet + memcpy(->data) */
            memcpy(pkt, &nsv->ahead[i], sizeof(AVPacket));
            nsv->ahead[i].data = NULL; /* we ate that one */
            return pkt->size;
        }
    }

    /* this restaurant is not approvisionned :^] */
    return -1;
}

static int nsv_read_seek(AVFormatContext *s, int stream_index, int64_t timestamp, int flags)
{
#if 0
    NSVContext *avi = s->priv_data;
    AVStream *st;
    NSVStream *ast;
    int frame_number, i;
    int64_t pos;
#endif

    return -1;
}

static int nsv_read_close(AVFormatContext *s)
{
/*     int i; */
    NSVContext *nsv = s->priv_data;

    if (nsv->index_entries)
        av_free(nsv->nsvf_index_data);

#if 0

    for(i=0;i<s->nb_streams;i++) {
        AVStream *st = s->streams[i];
        NSVStream *ast = st->priv_data;
        if(ast){
            av_free(ast->index_entries);
            av_free(ast);
        }
        av_free(st->codec->palctrl);
    }

#endif
    return 0;
}

static int nsv_probe(AVProbeData *p)
{
    int i;
//    PRINT(("nsv_probe(), buf_size %d\n", p->buf_size));
    /* check file header */
    /* streamed files might not have any header */
    if (p->buf[0] == 'N' && p->buf[1] == 'S' &&
        p->buf[2] == 'V' && (p->buf[3] == 'f' || p->buf[3] == 's'))
        return AVPROBE_SCORE_MAX;
    /* XXX: do streamed files always start at chunk boundary ?? */
    /* or do we need to search NSVs in the byte stream ? */
    /* seems the servers don't bother starting clean chunks... */
    /* sometimes even the first header is at 9KB or something :^) */
    for (i = 1; i < p->buf_size - 3; i++) {
        if (p->buf[i+0] == 'N' && p->buf[i+1] == 'S' &&
            p->buf[i+2] == 'V' && p->buf[i+3] == 's')
            return AVPROBE_SCORE_MAX-20;
    }
    /* so we'll have more luck on extension... */
    if (match_ext(p->filename, "nsv"))
        return AVPROBE_SCORE_MAX/2;
    /* FIXME: add mime-type check */
    return 0;
}

AVInputFormat nsv_demuxer = {
    "nsv",
    "NullSoft Video format",
    sizeof(NSVContext),
    nsv_probe,
    nsv_read_header,
    nsv_read_packet,
    nsv_read_close,
    nsv_read_seek,
};