nut.c

ffmpeg源码分析

    int64_t cur= url_ftell(bc);
    int size= cur - start - get_length(nut->written_packet_size)/7 - 8;

    if(calculate_checksum)
        size += 4;

    if(size != nut->written_packet_size){
        int i;

        assert( size <= nut->written_packet_size );

        url_fseek(bc, start + 8, SEEK_SET);
        for(i=get_length(size); i < get_length(nut->written_packet_size); i+=7)
            put_byte(bc, 0x80);
        put_v(bc, size);

        url_fseek(bc, cur, SEEK_SET);
        nut->written_packet_size= size; //FIXME may fail if multiple updates with differing sizes, as get_length may differ

        if(calculate_checksum)
            put_be32(bc, get_checksum(bc));
    }

    return 0;
}

static int nut_write_header(AVFormatContext *s)
{
    NUTContext *nut = s->priv_data;
    ByteIOContext *bc = &s->pb;
    AVCodecContext *codec;
    int i, j, tmp_time, tmp_flags,tmp_stream, tmp_mul, tmp_size, tmp_fields;

    nut->avf= s;

    nut->stream =
        av_mallocz(sizeof(StreamContext)*s->nb_streams);


    put_buffer(bc, ID_STRING, strlen(ID_STRING));
    put_byte(bc, 0);
    nut->packet_start[2]= url_ftell(bc);

    /* main header */
    put_be64(bc, MAIN_STARTCODE);
    put_packetheader(nut, bc, 120+5*256, 1);
    put_v(bc, 2); /* version */
    put_v(bc, s->nb_streams);
    put_v(bc, MAX_DISTANCE);
    put_v(bc, MAX_SHORT_DISTANCE);

    put_v(bc, nut->rate_num=1);
    put_v(bc, nut->rate_den=2);
    put_v(bc, nut->short_startcode=0x4EFE79);

    build_frame_code(s);
    assert(nut->frame_code['N'].flags == FLAG_INVALID);

    tmp_time= tmp_flags= tmp_stream= tmp_mul= tmp_size= /*tmp_res=*/ INT_MAX;
    for(i=0; i<256;){
        tmp_fields=0;
        tmp_size= 0;
        if(tmp_time   != nut->frame_code[i].timestamp_delta) tmp_fields=1;
        if(tmp_mul    != nut->frame_code[i].size_mul       ) tmp_fields=2;
        if(tmp_stream != nut->frame_code[i].stream_id_plus1) tmp_fields=3;
        if(tmp_size   != nut->frame_code[i].size_lsb       ) tmp_fields=4;
//        if(tmp_res    != nut->frame_code[i].res            ) tmp_fields=5;

        tmp_time  = nut->frame_code[i].timestamp_delta;
        tmp_flags = nut->frame_code[i].flags;
        tmp_stream= nut->frame_code[i].stream_id_plus1;
        tmp_mul   = nut->frame_code[i].size_mul;
        tmp_size  = nut->frame_code[i].size_lsb;
//        tmp_res   = nut->frame_code[i].res;

        for(j=0; i<256; j++,i++){
            if(nut->frame_code[i].timestamp_delta != tmp_time  ) break;
            if(nut->frame_code[i].flags           != tmp_flags ) break;
            if(nut->frame_code[i].stream_id_plus1 != tmp_stream) break;
            if(nut->frame_code[i].size_mul        != tmp_mul   ) break;
            if(nut->frame_code[i].size_lsb        != tmp_size+j) break;
//            if(nut->frame_code[i].res             != tmp_res   ) break;
        }
        if(j != tmp_mul - tmp_size) tmp_fields=6;

        put_v(bc, tmp_flags);
        put_v(bc, tmp_fields);
        if(tmp_fields>0) put_s(bc, tmp_time);
        if(tmp_fields>1) put_v(bc, tmp_mul);
        if(tmp_fields>2) put_v(bc, tmp_stream);
        if(tmp_fields>3) put_v(bc, tmp_size);
        if(tmp_fields>4) put_v(bc, 0 /*tmp_res*/);
        if(tmp_fields>5) put_v(bc, j);
    }

    update_packetheader(nut, bc, 0, 1);

    /* stream headers */
    for (i = 0; i < s->nb_streams; i++)
    {
        int nom, denom, ssize;

        codec = s->streams[i]->codec;

        put_be64(bc, STREAM_STARTCODE);
        put_packetheader(nut, bc, 120 + codec->extradata_size, 1);
        put_v(bc, i /*s->streams[i]->index*/);
        switch(codec->codec_type){
        case CODEC_TYPE_VIDEO: put_v(bc, 0); break;
        case CODEC_TYPE_AUDIO: put_v(bc, 1); break;
//        case CODEC_TYPE_TEXT : put_v(bc, 2); break;
        case CODEC_TYPE_DATA : put_v(bc, 3); break;
        default: return -1;
        }
        if (codec->codec_tag)
            put_vb(bc, codec->codec_tag);
        else if (codec->codec_type == CODEC_TYPE_VIDEO)
        {
            put_vb(bc, codec_get_bmp_tag(codec->codec_id));
        }
        else if (codec->codec_type == CODEC_TYPE_AUDIO)
        {
            put_vb(bc, codec_get_wav_tag(codec->codec_id));
        }
        else
            put_vb(bc, 0);

        ff_parse_specific_params(codec, &nom, &ssize, &denom);

        nut->stream[i].rate_num= nom;
        nut->stream[i].rate_den= denom;
        av_set_pts_info(s->streams[i], 60, denom, nom);

        put_v(bc, codec->bit_rate);
        put_vb(bc, 0); /* no language code */
        put_v(bc, nom);
        put_v(bc, denom);
        if(nom / denom < 1000)
            nut->stream[i].msb_timestamp_shift = 7;
        else
            nut->stream[i].msb_timestamp_shift = 14;
        put_v(bc, nut->stream[i].msb_timestamp_shift);
        put_v(bc, codec->has_b_frames);
        put_byte(bc, 0); /* flags: 0x1 - fixed_fps, 0x2 - index_present */

        if(codec->extradata_size){
            put_v(bc, 1);
            put_v(bc, codec->extradata_size);
            put_buffer(bc, codec->extradata, codec->extradata_size);
        }
        put_v(bc, 0); /* end of codec specific headers */

        switch(codec->codec_type)
        {
            case CODEC_TYPE_AUDIO:
                put_v(bc, codec->sample_rate);
                put_v(bc, 1);
                put_v(bc, codec->channels);
                break;
            case CODEC_TYPE_VIDEO:
                put_v(bc, codec->width);
                put_v(bc, codec->height);
                put_v(bc, codec->sample_aspect_ratio.num);
                put_v(bc, codec->sample_aspect_ratio.den);
                put_v(bc, 0); /* csp type -- unknown */
                break;
            default:
                break;
        }
        update_packetheader(nut, bc, 0, 1);
    }

    /* info header */
    put_be64(bc, INFO_STARTCODE);
    put_packetheader(nut, bc, 30+strlen(s->author)+strlen(s->title)+
        strlen(s->comment)+strlen(s->copyright)+strlen(LIBAVFORMAT_IDENT), 1);
    if (s->author[0])
    {
        put_v(bc, 9); /* type */
        put_str(bc, s->author);
    }
    if (s->title[0])
    {
        put_v(bc, 10); /* type */
        put_str(bc, s->title);
    }
    if (s->comment[0])
    {
        put_v(bc, 11); /* type */
        put_str(bc, s->comment);
    }
    if (s->copyright[0])
    {
        put_v(bc, 12); /* type */
        put_str(bc, s->copyright);
    }
    /* encoder */
    if(!(s->streams[0]->codec->flags & CODEC_FLAG_BITEXACT)){
        put_v(bc, 13); /* type */
        put_str(bc, LIBAVFORMAT_IDENT);
    }

    put_v(bc, 0); /* eof info */
    update_packetheader(nut, bc, 0, 1);

    put_flush_packet(bc);

    return 0;
}

static int nut_write_packet(AVFormatContext *s, AVPacket *pkt)
{
    NUTContext *nut = s->priv_data;
    StreamContext *stream= &nut->stream[pkt->stream_index];
    ByteIOContext *bc = &s->pb;
    int key_frame = 0, full_pts=0;
    AVCodecContext *enc;
    int64_t coded_pts;
    int frame_type, best_length, frame_code, flags, i, size_mul, size_lsb, time_delta;
    const int64_t frame_start= url_ftell(bc);
    int64_t pts= pkt->pts;
    int size= pkt->size;
    int stream_index= pkt->stream_index;

    enc = s->streams[stream_index]->codec;
    key_frame = !!(pkt->flags & PKT_FLAG_KEY);

    frame_type=0;
    if(frame_start + size + 20 - FFMAX(nut->packet_start[1], nut->packet_start[2]) > MAX_DISTANCE)
        frame_type=2;
    if(key_frame && !stream->last_key_frame)
        frame_type=2;

    if(frame_type>1){
        int64_t global_ts= av_rescale(pts, stream->rate_den*(int64_t)nut->rate_num, stream->rate_num*(int64_t)nut->rate_den);
        reset(s, global_ts);
        put_be64(bc, KEYFRAME_STARTCODE);
        put_v(bc, global_ts);
    }
    assert(stream->last_pts != AV_NOPTS_VALUE);
    coded_pts = pts & ((1<<stream->msb_timestamp_shift)-1);
    if(lsb2full(stream, coded_pts) != pts)
        full_pts=1;

    if(full_pts)
        coded_pts= pts + (1<<stream->msb_timestamp_shift);

    best_length=INT_MAX;
    frame_code= -1;
    for(i=0; i<256; i++){
        int stream_id_plus1= nut->frame_code[i].stream_id_plus1;
        int fc_key_frame;
        int length=0;
        size_mul= nut->frame_code[i].size_mul;
        size_lsb= nut->frame_code[i].size_lsb;
        time_delta= nut->frame_code[i].timestamp_delta;
        flags= nut->frame_code[i].flags;

        assert(size_mul > size_lsb);

        if(stream_id_plus1 == 0) length+= get_length(stream_index);
        else if(stream_id_plus1 - 1 != stream_index)
            continue;
        fc_key_frame= !!(flags & FLAG_KEY_FRAME);

        assert(key_frame==0 || key_frame==1);
        if(fc_key_frame != key_frame)
            continue;

        if(flags & FLAG_DATA_SIZE){
            if(size % size_mul != size_lsb)
                continue;
            length += get_length(size / size_mul);
        }else if(size != size_lsb)
            continue;

        if(full_pts && time_delta)
            continue;

        if(!time_delta){
            length += get_length(coded_pts);
        }else{
            if(time_delta != pts - stream->last_pts)
                continue;
        }

        if(length < best_length){
            best_length= length;
            frame_code=i;
        }
//    av_log(s, AV_LOG_DEBUG, "%d %d %d %d %d %d %d %d %d %d\n", key_frame, frame_type, full_pts, size, stream_index, flags, size_mul, size_lsb, stream_id_plus1, length);
    }

    assert(frame_code != -1);
    flags= nut->frame_code[frame_code].flags;
    size_mul= nut->frame_code[frame_code].size_mul;
    size_lsb= nut->frame_code[frame_code].size_lsb;
    time_delta= nut->frame_code[frame_code].timestamp_delta;
#ifdef TRACE
    best_length /= 7;
    best_length ++; //frame_code
    if(frame_type==2){
        best_length += 8; // startcode
    }
    av_log(s, AV_LOG_DEBUG, "kf:%d ft:%d pt:%d fc:%2X len:%2d size:%d stream:%d flag:%d mul:%d lsb:%d s+1:%d pts_delta:%d pts:%lld fs:%lld\n", key_frame, frame_type, full_pts ? 1 : 0, frame_code, best_length, size, stream_index, flags, size_mul, size_lsb, nut->frame_code[frame_code].stream_id_plus1,(int)(pts - stream->last_pts), pts, frame_start);
//    av_log(s, AV_LOG_DEBUG, "%d %d %d\n", stream->lru_pts_delta[0], stream->lru_pts_delta[1], stream->lru_pts_delta[2]);
#endif

    assert(frame_type != 1); //short startcode not implemented yet
    put_byte(bc, frame_code);

    if(nut->frame_code[frame_code].stream_id_plus1 == 0)
        put_v(bc, stream_index);
    if (!time_delta){
        put_v(bc, coded_pts);
    }
    if(flags & FLAG_DATA_SIZE)
        put_v(bc, size / size_mul);
    else
        assert(size == size_lsb);
    if(size > MAX_DISTANCE){
        assert(frame_type > 1);
    }

    put_buffer(bc, pkt->data, size);

    update(nut, stream_index, frame_start, frame_type, frame_code, key_frame, size, pts);

    return 0;
}

static int nut_write_trailer(AVFormatContext *s)
{
    NUTContext *nut = s->priv_data;
    ByteIOContext *bc = &s->pb;

#if 0
    int i;

    /* WRITE INDEX */

    for (i = 0; s->nb_streams; i++)
    {
        put_be64(bc, INDEX_STARTCODE);
        put_packetheader(nut, bc, 64, 1);
        put_v(bc, s->streams[i]->id);
        put_v(bc, ...);
        update_packetheader(nut, bc, 0, 1);
    }
#endif

    put_flush_packet(bc);

    av_freep(&nut->stream);

    return 0;
}
#endif //CONFIG_MUXERS

static int nut_probe(AVProbeData *p)
{
    int i;
    uint64_t code= 0xff;

    for (i = 0; i < p->buf_size; i++) {
        code = (code << 8) | p->buf[i];
        if (code == MAIN_STARTCODE)
            return AVPROBE_SCORE_MAX;
    }
    return 0;
}

static int decode_main_header(NUTContext *nut){
    AVFormatContext *s= nut->avf;
    ByteIOContext *bc = &s->pb;
    uint64_t tmp;
    int i, j, tmp_stream, tmp_mul, tmp_time, tmp_size, count, tmp_res;

    get_packetheader(nut, bc, 1);

    tmp = get_v(bc);
    if (tmp != 2){
        av_log(s, AV_LOG_ERROR, "bad version (%"PRId64")\n", tmp);
        return -1;
    }

    nut->stream_count = get_v(bc);
    if(nut->stream_count > MAX_STREAMS){
        av_log(s, AV_LOG_ERROR, "too many streams\n");
        return -1;
    }
    nut->max_distance = get_v(bc);
    nut->max_short_distance = get_v(bc);
    nut->rate_num= get_v(bc);
    nut->rate_den= get_v(bc);
    nut->short_startcode= get_v(bc);
    if(nut->short_startcode>>16 != 'N'){
        av_log(s, AV_LOG_ERROR, "invalid short startcode %X\n", nut->short_startcode);
        return -1;
    }

    for(i=0; i<256;){
        int tmp_flags = get_v(bc);
        int tmp_fields= get_v(bc);
        if(tmp_fields>0) tmp_time  = get_s(bc);
        if(tmp_fields>1) tmp_mul   = get_v(bc);
        if(tmp_fields>2) tmp_stream= get_v(bc);
        if(tmp_fields>3) tmp_size  = get_v(bc);
        else             tmp_size  = 0;
        if(tmp_fields>4) tmp_res   = get_v(bc);
        else             tmp_res   = 0;
        if(tmp_fields>5) count     = get_v(bc);
        else             count     = tmp_mul - tmp_size;

        while(tmp_fields-- > 6)
           get_v(bc);

        if(count == 0 || i+count > 256){
            av_log(s, AV_LOG_ERROR, "illegal count %d at %d\n", count, i);
            return -1;
        }
        if(tmp_stream > nut->stream_count + 1){
            av_log(s, AV_LOG_ERROR, "illegal stream number\n");
            return -1;
        }

        for(j=0; j<count; j++,i++){
            nut->frame_code[i].flags           = tmp_flags ;
            nut->frame_code[i].timestamp_delta = tmp_time  ;
            nut->frame_code[i].stream_id_plus1 = tmp_stream;
            nut->frame_code[i].size_mul        = tmp_mul   ;
            nut->frame_code[i].size_lsb        = tmp_size+j;
            nut->frame_code[i].reserved_count  = tmp_res   ;
        }
    }
    if(nut->frame_code['N'].flags != FLAG_INVALID){
        av_log(s, AV_LOG_ERROR, "illegal frame_code table\n");
        return -1;
    }

    if(check_checksum(bc)){
        av_log(s, AV_LOG_ERROR, "Main header checksum mismatch\n");
        return -1;
    }

    return 0;
}

static int decode_stream_header(NUTContext *nut){
    AVFormatContext *s= nut->avf;
    ByteIOContext *bc = &s->pb;
    int class, nom, denom, stream_id;
    uint64_t tmp;
    AVStream *st;

    get_packetheader(nut, bc, 1);
    stream_id= get_v(bc);
    if(stream_id >= nut->stream_count || s->streams[stream_id])
        return -1;

    st = av_new_stream(s, stream_id);
    if (!st)
        return AVERROR_NOMEM;

    class = get_v(bc);
    tmp = get_vb(bc);
    st->codec->codec_tag= tmp;
    switch(class)
    {
        case 0:
            st->codec->codec_type = CODEC_TYPE_VIDEO;
            st->codec->codec_id = codec_get_bmp_id(tmp);
            if (st->codec->codec_id == CODEC_ID_NONE)
                av_log(s, AV_LOG_ERROR, "Unknown codec?!\n");
            break;
        case 1:
        case 32: //compatibility
            st->codec->codec_type = CODEC_TYPE_AUDIO;
            st->codec->codec_id = codec_get_wav_id(tmp);
            if (st->codec->codec_id == CODEC_ID_NONE)
                av_log(s, AV_LOG_ERROR, "Unknown codec?!\n");
            break;
        case 2:
//            st->codec->codec_type = CODEC_TYPE_TEXT;
//            break;
        case 3:
            st->codec->codec_type = CODEC_TYPE_DATA;
            break;