mirror of https://github.com/mpv-player/mpv
659 lines
18 KiB
Plaintext
659 lines
18 KiB
Plaintext
NUT Open Container Format DRAFT 20041005 (Michael's experimental fork)
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----------------------------------------
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Intro:
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Features / goals:
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(supported by the format, not necessary by a specific implementation)
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Simple
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use the same encoding for nearly all fields
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simple decoding, so slow cpus (and embedded systems) can handle it
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Extendible
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no limit for the possible values for all fields (using universal vlc)
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allow adding of new headers in the future
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allow adding more fields at the end of headers
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Compact
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~0.2% overhead, for normal bitrates
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index is <10kb per hour (1 keyframe every 3sec)
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a usual header for a file is about 100bytes (audio + video headers together)
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a packet header is about ~1-8 bytes
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Error resistant
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seeking / playback without an index
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headers & index can be repeated
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damaged files can be played back with minimal data lost and fast
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resyncing times
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Definitions:
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MUST the specific part must be done to conform to this standard
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SHOULD its recommanded to be done that way but its not strictly required
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Syntax:
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Type definitions:
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f(x) n fixed bits in big-endian order
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u(x) unsigned number encoded in x bits in MSB first order
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v
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value=0
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do{
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more_data u(1)
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data u(7)
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value= 128*value + data
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}while(more_data)
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s
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temp v
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temp++
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if(temp&1) value= -(temp>>1)
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else value= (temp>>1)
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b (binary data or string)
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for(i=0; i<length; i++){
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data[i] u(8)
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}
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Note: strings MUST be encoded in utf8
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vb
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length v
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value b
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Bitstream syntax:
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packet header
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forward ptr v
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align_byte
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while(not byte aligned)
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one f(1)
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reserved_bytes
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for(i=0; i<forward_ptr - length_of_non_reserved; i++)
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reserved u(8)
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a demuxer MUST ignore any reserved bytes
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a muxer MUST NOT write any reserved bytes, as this would make it
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inpossible to add new fields at the end of packets in the future in
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a compatible way
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main header:
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main_startcode f(64)
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packet header
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branch v
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version v
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stream_count v
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max_distance v
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max_index_distance v
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global_time_base_nom v
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global_time_base_denom v
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for(i=0; i<256; ){
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tmp_flag v
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tmp_fields v
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if(tmp_fields>0) tmp_timestamp s
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if(tmp_fields>1) tmp_mul v
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if(tmp_fields>2) tmp_stream v
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if(tmp_fields>3) tmp_size v
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else tmp_size=0
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if(tmp_fields>4) tmp_res v
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else tmp_res=0
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if(tmp_fields>5) count v
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else count= tmp_mul - tmp_size
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for(j=6; j<tmp_fields; j++){
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tmp_reserved[i] v
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}
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for(j=0; j<count && i<256; j++, i++){
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flags[i]= tmp_flag;
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stream_id_plus1[i]= tmp_stream;
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data_size_mul[i]= tmp_mul;
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data_size_lsb[i]= tmp_size + j;
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timestamp_delta[i]= tmp_timestamp;
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reserved_count[i]= tmp_res;
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}
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}
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reserved_bytes
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checksum u(32)
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stream_header:
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stream_startcode f(64)
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packet_header
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stream_id v
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stream_class v
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fourcc vb
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average_bitrate v
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time_base_nom v
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time_base_denom v
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msb_timestamp_shift v
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decode_delay v
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fixed_fps u(1)
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reserved u(6)
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codec_specific_data vb
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video_stream_header:
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stream_header
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width v
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height v
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sample_width v
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sample_height v
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colorspace_type v
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reserved_bytes
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checksum u(32)
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audio_stream_header:
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stream_header
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samplerate_nom v
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samplerate_denom v
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channel_count v
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reserved_bytes
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checksum u(32)
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frame
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frame_code f(8)
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if(stream_id_plus1[frame_code]==0){
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stream_id v
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}
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if(timestamp_delta[frame_code]==0){
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coded_timestamp v
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}
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if(flags[frame_code]&1){
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data_size_msb v
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}
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for(i=0; i<reserved_count[frame_code]; i++)
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reserved v
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data
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Index:
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index_startcode f(64)
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packet header
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stream_id v
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index_length v
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for(i=0; i<index_length; i++){
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index_timestamp v
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index_position v
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}
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reserved_bytes
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checksum u(32)
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info_packet: (optional)
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info_startcode f(64)
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packet header
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for(;;){
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id v
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if(id==0) break
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name= info_table[id][0]
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type= info_table[id][1]
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if(type==NULL)
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type vb
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if(name==NULL)
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name vb
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if(type=="v")
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value v
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else
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value vb
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}
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reserved_bytes
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checksum u(32)
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sync_point
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frame_startcode f(64)
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global_timestamp v
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file
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file_id_string
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while(!eof && next_code != index_startcode){
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main_header
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for(i=0; i<stream_count; i++){
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if(next_packet==video_stream_header)
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video_stream_header
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else
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audio_stream_header
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}
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while(next_code != main_startcode){
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if(next_code == info_startcode)
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info_packet
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else{
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if(next_code == frame_startcode)
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sync_point
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frame
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}
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}
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}
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index
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forward_ptr
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size of the packet (exactly the distance from the first byte of the
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startcode of the current packet to the first byte of the following packet
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file_id_string
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"nut/multimedia container\0"
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*_startcode
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all startcodes start with 'N'
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main_startcode
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0x7A561F5F04ADULL + (((uint64_t)('N'<<8) + 'M')<<48)
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stream_starcode
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0x11405BF2F9DBULL + (((uint64_t)('N'<<8) + 'S')<<48)
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frame_startcode
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0xE4ADEECA4569ULL + (((uint64_t)('N'<<8) + 'K')<<48)
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frame_startcodes SHOULD be placed immedeatly before a keyframe if the
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previous frame of the same stream was a non-keyframe, unless such
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non-keyframe - keyframe tansitions are very frequent
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index_startcode
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0xDD672F23E64EULL + (((uint64_t)('N'<<8) + 'X')<<48)
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info_startcode
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0xAB68B596BA78ULL + (((uint64_t)('N'<<8) + 'I')<<48)
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branch
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1 for my fork, 0 for the official nut container
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version
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2 for now
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max_distance
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max distance of frame_startcodes, the distance may only be larger if
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there is only a single frame between the 2 frame_startcodes
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this can be used by the demuxer to detect damaged frame headers if the
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damage results in a too long chain
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SHOULD be set to <=32768 or at least <=65536 unless there is a very good
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reason to set it higher otherwise reasonable error recovery will be
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impossible
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max_index_distance
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max distance of keyframes which are represented in the index, the
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distance between consecutive entries A and B may only be larger if
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there are no keyframes within this stream between A and B
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SHOULD be set to <=32768 or at least <=65536 unless there is a very good
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reason to set it higher
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stream_id
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Note: streams with a lower relative class MUST have a lower relative id
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so a stream with class 0 MUST allways have a id which is lower then any
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stream with class > 0
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stream_id MUST be < stream_count
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stream_class
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0 video
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32 audio
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64 subtiles
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Note the remaining values are reserved and MUST NOT be used
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a demuxer MUST ignore streams with reserved classes
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fourcc
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identification for the codec
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example: "H264"
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MUST contain 2 or 4 bytes, note, this might be increased in the future
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if needed
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time_base_nom / time_base_denom = time_base
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the number of timer ticks per second, this MUST be equal to the fps
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if the fixed_fps is 1
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time_base_denom MUST not be 0
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time_base_nom and time_base_denom MUST be relative prime
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time_base_nom MUST be < 2^31
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examples:
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fps time_base_nom time_base_denom
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30 30 1
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29.97 30000 1001
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23.976 24000 1001
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sample_rate sample_rate_mul time_base_nom time_base_denom
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44100 1 44100 1
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44100 64 11025 16
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48000 1024 375 8
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Note: the advantage to using a large sample_rate_mul is that the
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timestamps need fewer bits
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global_time_base_nom / global_time_base_denom = global_time_base
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the number of timer ticks per second
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global_time_base_denom MUST not be 0
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global_time_base_nom and global_time_base_denom MUST be relative prime
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global_time_base_nom MUST be < 2^31
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global_timestamp
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timestamp in global_time_base units
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when a global_timestamp is encountered the last_timestamp of all streams
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is set to the following:
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ln= global_time_base_denom*time_base_nom
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sn= global_timestamp
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d1= global_time_base_nom
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d2= time_base_denom
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last_timestamp= (ln/d1*sn + ln%d1*sn/d1)/d2
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Note, this calculation MUST be done with unsigned 64 bit integers, and
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is equivalent to (ln*sn)/(d1*d2) but this would require a 96bit integer
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msb_timestamp_shift
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amount of bits in lsb_timestamp
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MUST be <16
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decode_delay
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maximum time between input and output for a codec, used to generate dts
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from pts
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is 0 for streams without b frames, and 1 for streams with b frames, may
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be larger for future codecs
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fixed_fps
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1 indicates that the fps is fixed
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codec_specific_data
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private global data for a codec (could be huffman tables or ...)
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frame_code
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the meaning of this byte is stored in the main header
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the value 78 ('N') is forbidden to ensure that the byte is always
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different from the first byte of any startcode
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flags[frame_code]
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the bits of the flags from MSB to LSB are KD
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if D is 1 then data_size_msb is coded, otherwise data_size_msb is 0
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K is the keyframe_type
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0-> no keyframe,
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1-> keyframe,
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flags=4 can be used to mark illegal frame_code bytes
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frame_code=78 must have flags=4
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* frames MUST not depend(1) upon frames prior to the last
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frame_startcode
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depend(1) means dependancy on the container level (NUT) not dependancy
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on the codec level
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stream_id_plus1[frame_code]
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must be <250
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if its 0 then the stream_id is coded in the frame
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data_size_mul[frame_code]
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must be <16384
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data_size_lsb[frame_code]
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must be <16384
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timestamp_delta[frame_code]
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must be <16384 and >-16384
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data_size
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data_size= data_size_lsb + data_size_msb*data_size_mul;
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coded_timestamp
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if coded_timestamp < (1<<msb_timestamp_shift) then its a
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lsb timestamp, otherwise its a full timestamp + (1<<msb_timestamp_shift)
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lsb timestamps are converted to full timesamps by:
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mask = (1<<msb_timestamp_shift)-1;
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delta= last_timestamp - mask/2
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timestamp= ((timestamp_lsb-delta)&mask) + delta
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a full timestamp must be used if there is no reference timestamp
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available after the last frame_startcode with the current stream_id
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lsb_timestamp
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least significant bits of the timestamp in time_base precission
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Example: IBBP display order
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keyframe timestamp=0 -> timestamp=0
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frame lsb_timestamp=3 -> timestamp=3
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frame lsb_timestamp=1 -> timestamp=1
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frame lsb_timestamp=2 -> timestamp=2
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...
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keyframe msb_timestamp=257 -> timestamp=257
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frame lsb_timestamp=255->timestamp=255
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frame lsb_timestamp=0 -> timestamp=256
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frame lsb_timestamp=4 -> timestamp=260
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frame lsb_timestamp=2 -> timestamp=258
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frame lsb_timestamp=3 -> timestamp=259
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all timestamps of keyframes of a single stream MUST be monotone
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dts
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dts are calculated by using a decode_delay+1 sized buffer for each
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stream, into which the current pts is inserted and the element with
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the smallest value is removed, this is then the current dts
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this buffer is initalized with decode_delay -1 elements
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all frames with dts == timestamp must be monotone, that means a frame
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which occures later in the stream must have a larger or equal dts
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then an earlier frame
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FIXME rename timestamp* to pts* ?
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width/height
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MUST be set to the coded width/height
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sample_width/sample_height (aspect ratio)
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sample_width is the horizontal distance between samples
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sample_width and sample_height MUST be relative prime if not zero
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MUST be 0 if unknown
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colorspace_type
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0 unknown
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1 ITU Rec 624 / ITU Rec 601 Y range: 16..235 Cb/Cr range: 16..240
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2 ITU Rec 709 Y range: 16..235 Cb/Cr range: 16..240
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17 ITU Rec 624 / ITU Rec 601 Y range: 0..255 Cb/Cr range: 0..255
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18 ITU Rec 709 Y range: 0..255 Cb/Cr range: 0..255
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samplerate_nom / samplerate_denom = samplerate
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the number of samples per second
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checksum
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adler32 checksum
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index_timestamp
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value of the timetamp of a keyframe relative to the last keyframe
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stored in this index
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index_position
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position in bytes of the first byte of a keyframe, relative to the
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last keyframe stored in this index
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there MUST be no keyframe with the same stream_id as this index between
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2 consecutive index entries if they are more then max_index_distance
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appart
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id
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the id of the type/name pair, so its more compact
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0 means end
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type
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for example: "UTF8" -> String or "JPEG" -> jpeg image
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Note: nonstandard fields should be prefixed by "X-"
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Note: MUST be less than 6 byte long (might be increased to 64 later)
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name
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the name of the info entry, valid names are
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"TotalTime" total length of the stream in msecs
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"StreamId" the stream(s) to which the info packet applies
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"StartTimestamp"
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"EndTimestamp" the time range in msecs to which the info applies
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"SegmentId" a unique id for the streams + time specified
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"Author"
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"Description"
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"Copyright"
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"Encoder" the name & version of the software used for encoding
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"Title"
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"Cover" an image of the (cd,dvd,vhs,..) cover (preferable PNG or JPEG)
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"Source" "DVD", "VCD", "CD", "MD", "FM radio", "VHS", "TV",
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"LD"
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Optional: appended PAL,NTSC,SECAM, ... in parentheses
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"CaptureDevice" "BT878", "BT848", "webcam", ... (more exact names are fine too)
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"CreationTime" "2003-01-20 20:13:15Z", ...
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(ISO 8601 format, see http://www.cl.cam.ac.uk/~mgk25/iso-time.html)
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Note: dont forget the timezone
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"ReplayGain"
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"Keywords"
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"Language" ISO 639 and ISO 3166 for language/country code
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something like "usen" (US english), can be 0 if unknown
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and "multi" if several languages
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see http://www.loc.gov/standards/iso639-2/englangn.html
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and http://www.din.de/gremien/nas/nabd/iso3166ma/codlstp1/en_listp1.htmlthe language code
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"Disposition" "original", "dub" (translated), "comment", "lyrics", "karaoke"
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Note: if someone needs some others, please tell us about them, so we can
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add them to the official standard (if they are sane)
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Note: nonstandard fields should be prefixed by "X-"
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Note: MUST be less than 64 bytes long
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value
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value of this name/type pair
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stuffing
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0x80 can be placed infront of any type v entry for stuffing
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purposes
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info_table[][2]={
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{NULL , NULL }, // end
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{NULL , NULL },
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{NULL , "UTF8"},
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{NULL , "v"},
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{NULL , "s"},
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{"StreamId" , "v"},
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{"SegmentId" , "v"},
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{"StartTimestamp" , "v"},
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{"EndTimestamp" , "v"},
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{"Author" , "UTF8"},
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{"Titel" , "UTF8"},
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{"Language" , "UTF8"},
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{"Description" , "UTF8"},
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{"Copyright" , "UTF8"},
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{"Encoder" , "UTF8"},
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{"Keyword" , "UTF8"},
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{"Cover" , "JPEG"},
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{"Cover" , "PNG"},
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{"Disposition" , "UTF8"},
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};
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Structure:
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the headers MUST be in exactly the following order (to simplify demuxer design)
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main header
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stream_header (id=0)
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stream_header (id=1)
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...
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stream_header (id=n)
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headers may be repated, but if they are then they MUST all be repeated together
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and repeated headers MUST be identical
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headers MAY only repeated at the closest possible positions after 2^x where x is
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an integer and the file end, so the headers may be repeated at 4102 if thats the
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closest possition after 2^12=4096 at which the headers can be placed
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headers MUST be placed at least at the begin of the file and immedeatly before
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the index or at the file end if there is no index
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headers MUST be repeated at least twice (so they exist 3 times in a file)
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a demuxer MUST not demux a stream which contains more than one stream, or which
|
|
is wrapped in a structure to facilitate more than one stream or otherwise
|
|
duplicate the role of a container. any such file is to be considered invalid
|
|
|
|
info packets which describe the whole file or individual streams/tracks must be
|
|
placed before any video/audio/... frames
|
|
|
|
Index
|
|
Note: in case of realtime streaming there is no end, so no index there either
|
|
|
|
Info packets
|
|
the info_packet can be repeated, it can also contain different names & values
|
|
each time but only if allso the time is different
|
|
Info packets can be used to describe the file or some part of it (chapters)
|
|
|
|
info packets, SHOULD be placed at the begin of the file at least
|
|
for realtime streaming info packets will normally be transmitted when they apply
|
|
for example, the current song title & artist of the currently shown music video
|
|
|
|
Unknown packets
|
|
MUST be ignored by the demuxer
|
|
|
|
demuxer (non-normative)
|
|
|
|
in the absence of valid header at beginning, players SHOULD search for backup
|
|
headers starting at offset 2^x for each x players SHOULD end their search from a
|
|
particular offset when any startcode is found (including syncpoint)
|
|
|
|
|
|
Sample code (GPL, & untested)
|
|
|
|
typedef BufferContext{
|
|
uint8_t *buf;
|
|
uint8_t *buf_ptr;
|
|
}BufferContext;
|
|
|
|
static inline uint64_t get_bytes(BufferContext *bc, int count){
|
|
uint64_t val=0;
|
|
|
|
assert(count>0 && count<9)
|
|
|
|
for(i=0; i<count; i++){
|
|
val <<=8;
|
|
val += *(bc->buf_ptr++);
|
|
}
|
|
|
|
return val;
|
|
}
|
|
|
|
static inline void put_bytes(BufferContext *bc, int count, uint64_t val){
|
|
uint64_t val=0;
|
|
|
|
assert(count>0 && count<9)
|
|
|
|
for(i=count-1; i>=0; i--){
|
|
*(bc->buf_ptr++)= val >> (8*i);
|
|
}
|
|
|
|
return val;
|
|
}
|
|
|
|
static inline uint64_t get_v(BufferContext *bc){
|
|
uint64_t val= 0;
|
|
|
|
for(; space_left(bc) > 0; ){
|
|
int tmp= *(bc->buf_ptr++);
|
|
if(tmp&0x80)
|
|
val= (val<<7) + tmp - 0x80;
|
|
else
|
|
return (val<<7) + tmp;
|
|
}
|
|
|
|
return -1;
|
|
}
|
|
|
|
static inline int put_v(BufferContext *bc, uint64_t val){
|
|
int i;
|
|
|
|
if(space_left(bc) < 9) return -1;
|
|
|
|
val &= 0x7FFFFFFFFFFFFFFFULL; // FIXME can only encode upto 63 bits currently
|
|
for(i=7; ; i+=7){
|
|
if(val>>i == 0) break;
|
|
}
|
|
|
|
for(i-=7; i>0; i-=7){
|
|
*(bc->buf_ptr++)= 0x80 | (val>>i);
|
|
}
|
|
*(bc->buf_ptr++)= val&0x7F;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int64_t get_dts(int64_t pts, int64_t *pts_cache, int delay, int reset){
|
|
if(reset) memset(pts_cache, -1, delay*sizeof(int64_t));
|
|
|
|
while(delay--){
|
|
int64_t t= pts_cache[delay];
|
|
if(t < pts){
|
|
pts_cache[delay]= pts;
|
|
pts= t;
|
|
}
|
|
}
|
|
|
|
return pts;
|
|
}
|
|
|
|
Authors
|
|
|
|
Folks from MPlayer Developers Mailinglist (http://www.mplayehrq.hu/).
|
|
Authors in ABC-order: (FIXME! Tell us if we left you out)
|
|
Beregszaszi, Alex (alex@fsn.hu)
|
|
Bunkus, Moritz (moritz@bunkus.org)
|
|
Diedrich, Tobias (td@sim.uni-hannover.de)
|
|
Felker, Rich (dalias@aerifal.cx)
|
|
Franz, Fabian (FabianFranz@gmx.de)
|
|
Gereoffy, Arpad (arpi@thot.banki.hu)
|
|
Hess, Andreas (jaska@gmx.net)
|
|
Niedermayer, Michael (michaelni@gmx.at)
|