nutenc.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

        break;
    case CODEC_TYPE_VIDEO:
        put_v(bc, codec->width);
        put_v(bc, codec->height);

        if(codec->sample_aspect_ratio.num<=0 || codec->sample_aspect_ratio.den<=0){
            put_v(bc, 0);
            put_v(bc, 0);
        }else{
            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;
    }
    return 0;
}

static int add_info(ByteIOContext *bc, char *type, char *value){
    put_str(bc, type);
    put_s(bc, -1);
    put_str(bc, value);
    return 1;
}

static void write_globalinfo(NUTContext *nut, ByteIOContext *bc){
    AVFormatContext *s= nut->avf;
    ByteIOContext dyn_bc;
    uint8_t *dyn_buf=NULL;
    int count=0, dyn_size;

    url_open_dyn_buf(&dyn_bc);

    if(s->title    [0]) count+= add_info(&dyn_bc, "Title"    , s->title);
    if(s->author   [0]) count+= add_info(&dyn_bc, "Author"   , s->author);
    if(s->copyright[0]) count+= add_info(&dyn_bc, "Copyright", s->copyright);
    if(!(s->streams[0]->codec->flags & CODEC_FLAG_BITEXACT))
                        count+= add_info(&dyn_bc, "Encoder"  , LIBAVFORMAT_IDENT);

    put_v(bc, 0); //stream_if_plus1
    put_v(bc, 0); //chapter_id
    put_v(bc, 0); //timestamp_start
    put_v(bc, 0); //length

    put_v(bc, count);

    dyn_size= url_close_dyn_buf(&dyn_bc, &dyn_buf);
    put_buffer(bc, dyn_buf, dyn_size);
    av_free(dyn_buf);
}

static void write_headers(NUTContext *nut, ByteIOContext *bc){
    ByteIOContext dyn_bc;
    int i;

    url_open_dyn_buf(&dyn_bc);
    write_mainheader(nut, &dyn_bc);
    put_packet(nut, bc, &dyn_bc, 1, MAIN_STARTCODE);

    for (i=0; i < nut->avf->nb_streams; i++){
        AVCodecContext *codec = nut->avf->streams[i]->codec;

        url_open_dyn_buf(&dyn_bc);
        write_streamheader(nut, &dyn_bc, codec, i);
        put_packet(nut, bc, &dyn_bc, 1, STREAM_STARTCODE);
    }

    url_open_dyn_buf(&dyn_bc);
    write_globalinfo(nut, &dyn_bc);
    put_packet(nut, bc, &dyn_bc, 1, INFO_STARTCODE);

    nut->last_syncpoint_pos= INT_MIN;
    nut->header_count++;
}

static int write_header(AVFormatContext *s){
    NUTContext *nut = s->priv_data;
    ByteIOContext *bc = &s->pb;
    int i, j;

    nut->avf= s;

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

    for(i=0; i<s->nb_streams; i++){
        AVStream *st= s->streams[i];
        int ssize;
        AVRational time_base;
        ff_parse_specific_params(st->codec, &time_base.den, &ssize, &time_base.num);

        av_set_pts_info(st, 64, time_base.num, time_base.den);

        for(j=0; j<nut->time_base_count; j++){
            if(!memcmp(&time_base, &nut->time_base[j], sizeof(AVRational))){
                break;
            }
        }
        nut->time_base[j]= time_base;
        nut->stream[i].time_base= &nut->time_base[j];
        if(j==nut->time_base_count)
            nut->time_base_count++;

        if(av_q2d(time_base) >= 0.001)
            nut->stream[i].msb_pts_shift = 7;
        else
            nut->stream[i].msb_pts_shift = 14;
        nut->stream[i].max_pts_distance= FFMAX(1/av_q2d(time_base), 1);
    }

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

    put_buffer(bc, ID_STRING, strlen(ID_STRING));
    put_byte(bc, 0);

    write_headers(nut, bc);

    put_flush_packet(bc);

    //FIXME index

    return 0;
}

static int get_needed_flags(NUTContext *nut, StreamContext *nus, FrameCode *fc, AVPacket *pkt){
    int flags= 0;

    if(pkt->flags & PKT_FLAG_KEY                ) flags |= FLAG_KEY;
    if(pkt->stream_index != fc->stream_id       ) flags |= FLAG_STREAM_ID;
    if(pkt->size / fc->size_mul                 ) flags |= FLAG_SIZE_MSB;
    if(pkt->pts - nus->last_pts != fc->pts_delta) flags |= FLAG_CODED_PTS;
    if(pkt->size > 2*nut->max_distance          ) flags |= FLAG_CHECKSUM;
    if(FFABS(pkt->pts - nus->last_pts)
                         > nus->max_pts_distance) flags |= FLAG_CHECKSUM;

    return flags | (fc->flags & FLAG_CODED);
}

static int write_packet(AVFormatContext *s, AVPacket *pkt){
    NUTContext *nut = s->priv_data;
    StreamContext *nus= &nut->stream[pkt->stream_index];
    ByteIOContext *bc = &s->pb, dyn_bc;
    FrameCode *fc;
    int64_t coded_pts;
    int best_length, frame_code, flags, needed_flags, i;
    int key_frame = !!(pkt->flags & PKT_FLAG_KEY);
    int store_sp=0;

    if(1LL<<(20+3*nut->header_count) <= url_ftell(bc))
        write_headers(nut, bc);

    if(key_frame && !!(nus->last_flags & FLAG_KEY))
        store_sp= 1;

    if(pkt->size + 30/*FIXME check*/ + url_ftell(bc) >= nut->last_syncpoint_pos + nut->max_distance)
        store_sp= 1;

//FIXME: Ensure store_sp is 1 in the first place.

    if(store_sp){
        syncpoint_t *sp, dummy= {.pos= INT64_MAX};

        ff_nut_reset_ts(nut, *nus->time_base, pkt->dts);
        for(i=0; i<s->nb_streams; i++){
            AVStream *st= s->streams[i];
            int index= av_index_search_timestamp(st, pkt->dts, AVSEEK_FLAG_BACKWARD);
            if(index<0) dummy.pos=0;
            else        dummy.pos= FFMIN(dummy.pos, st->index_entries[index].pos);
        }
        sp= av_tree_find(nut->syncpoints, &dummy, ff_nut_sp_pos_cmp, NULL);

        nut->last_syncpoint_pos= url_ftell(bc);
        url_open_dyn_buf(&dyn_bc);
        put_t(nut, nus, &dyn_bc, pkt->dts);
        put_v(&dyn_bc, sp ? (nut->last_syncpoint_pos - sp->pos)>>4 : 0);
        put_packet(nut, bc, &dyn_bc, 1, SYNCPOINT_STARTCODE);

        ff_nut_add_sp(nut, nut->last_syncpoint_pos, 0/*unused*/, pkt->dts);
    }
    assert(nus->last_pts != AV_NOPTS_VALUE);

    coded_pts = pkt->pts & ((1<<nus->msb_pts_shift)-1);
    if(ff_lsb2full(nus, coded_pts) != pkt->pts)
        coded_pts= pkt->pts + (1<<nus->msb_pts_shift);

    best_length=INT_MAX;
    frame_code= -1;
    for(i=0; i<256; i++){
        int length= 0;
        FrameCode *fc= &nut->frame_code[i];
        int flags= fc->flags;

        if(flags & FLAG_INVALID)
            continue;
        needed_flags= get_needed_flags(nut, nus, fc, pkt);

        if(flags & FLAG_CODED){
            length++;
            flags = needed_flags;
        }

        if((flags & needed_flags) != needed_flags)
            continue;

        if((flags ^ needed_flags) & FLAG_KEY)
            continue;

        if(flags & FLAG_STREAM_ID)
            length+= get_length(pkt->stream_index);

        if(pkt->size % fc->size_mul != fc->size_lsb)
            continue;
        if(flags & FLAG_SIZE_MSB)
            length += get_length(pkt->size / fc->size_mul);

        if(flags & FLAG_CHECKSUM)
            length+=4;

        if(flags & FLAG_CODED_PTS)
            length += get_length(coded_pts);

        length*=4;
        length+= !(flags & FLAG_CODED_PTS);
        length+= !(flags & FLAG_CHECKSUM);

        if(length < best_length){
            best_length= length;
            frame_code=i;
        }
    }
    assert(frame_code != -1);
    fc= &nut->frame_code[frame_code];
    flags= fc->flags;
    needed_flags= get_needed_flags(nut, nus, fc, pkt);

    init_checksum(bc, av_crc04C11DB7_update, 0);
    put_byte(bc, frame_code);
    if(flags & FLAG_CODED){
        put_v(bc, (flags^needed_flags) & ~(FLAG_CODED));
        flags = needed_flags;
    }
    if(flags & FLAG_STREAM_ID)  put_v(bc, pkt->stream_index);
    if(flags & FLAG_CODED_PTS)  put_v(bc, coded_pts);
    if(flags & FLAG_SIZE_MSB)   put_v(bc, pkt->size / fc->size_mul);

    if(flags & FLAG_CHECKSUM)   put_le32(bc, get_checksum(bc));
    else                        get_checksum(bc);

    put_buffer(bc, pkt->data, pkt->size);
    nus->last_flags= flags;

    //FIXME just store one per syncpoint
    if(flags & FLAG_KEY)
        av_add_index_entry(
            s->streams[pkt->stream_index],
            nut->last_syncpoint_pos,
            pkt->pts,
            0,
            0,
            AVINDEX_KEYFRAME);

    return 0;
}

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

    while(nut->header_count<3)
        write_headers(nut, bc);
    put_flush_packet(bc);

    return 0;
}

AVOutputFormat nut_muxer = {
    "nut",
    "nut format",
    "video/x-nut",
    "nut",
    sizeof(NUTContext),
#ifdef CONFIG_LIBVORBIS
    CODEC_ID_VORBIS,
#elif defined(CONFIG_LIBMP3LAME)
    CODEC_ID_MP3,
#else
    CODEC_ID_MP2, /* AC3 needs liba52 decoder */
#endif
    CODEC_ID_MPEG4,
    write_header,
    write_packet,
    write_trailer,
    .flags = AVFMT_GLOBALHEADER,
    .codec_tag= (const AVCodecTag*[]){codec_bmp_tags, codec_wav_tags, 0},
};