nut format draft 0.02 Intro: Features / goals: (supported by the format, not necessary by a specific implementation) Simple use the same encoding for nearly all fields simple decoding, so slow cpus can handle it Extendible no limit for the possible values for all fields (using universal vlc) allow adding of new headers in the future allow adding more fields at the end of headers Compact ~0.2% overhead, for normal bitrates index is <10kb per hour (1 keyframe every 3sec) Error resistant seeking / playback without an index headers & index can be repeated audio packet reshuffle checksums to allow quick redownloading of damaged parts Definitions: MUST the specific part must be done to conform to this standard SHOULD its recommanded to be done that way but its not strictly required Syntax: Type definitions: v value=0 do{ more_data u(1) data u(7) value= 128*value + data }while(more_data) s temp v temp++ if(temp&1) value= -(temp>>1) else value= (temp>>1) b (binary data or string) length v for(i=0; i 0 streams should use low ids stream_class 0 video 32 audio 64 subtiles Note the remaining values are reserved and MUST NOT be used a decoder MUST ignore streams with reserved classes fourcc identification for the codec example: "H264" MUST contain 4 bytes, note, this might be increasd in the future if needed language_code ISO 639 and ISO 3166 for language/country code something like "usen" (US english), can be 0 if unknown see http://www.loc.gov/standards/iso639-2/englangn.html and http://www.din.de/gremien/nas/nabd/iso3166ma/codlstp1/en_listp1.html time_base_nom / time_base_denom = time_base the number of timer ticks per second, this MUST be equal to the fps if the fixed_fps is 1 time_base_denom MUST not be 0 time_base_nom and time_base_denom MUST be relative prime time_base_nom MUST be < 2^16 examples: fps time_base_nom time_base_denom 30 30 1 29.97 30000 1001 23.976 24000 1001 sample_rate sample_rate_mul time_base_nom time_base_denom 44100 1 44100 1 44100 64 11025 16 48000 1024 375 8 Note: the advantage to using a large sample_rate_mul is that the timestamps need fewer bits msb_timestamp_shift amount of bits msb_timestamp is shifted left before adding lsb_timestamp MUST be <16 fixed_fps 1 indicates that the fps is fixed codec_specific_data_type 0 end 1 native 2 bitmapinfoheader 3 waveformatex 4 imagedesc 5 sounddesc "native", means a simple api & container independanet storage form, for example some mpeg4-es headers codec_specific_data private global data for a codec (could be huffman tables or ...) msb_timestamp_flag indicates that the msb_timestamp is coded MUST be 1 for keyframes subpacket_type subpacket_count subpacket_size keyframe_flag 00 >1 constant constant 01 1 NA NA 10 >1 variable constant 11 >1 variable variable the only legal subpacket_type for video streams is 01, so video streams MUST NOT contain multiple subpackets per packet Note, if there are multiple subpackets then the timestamp of the packet is the timestamp of the first subpacket Note, if multiple subpackets are stored in one frame then the resulting framesize SHOULD be < 16kbyte and not more then 0.5 sec of data SHOULD be put in a single packet subpacket_count the number of subpackets, if not pressent then 1 keyframe_run[i] the number of subpackets with an identical keyframe_flag Note, the value of first flag is stored in the packet header is equal to subpacket count if not coded timestamp_diff[i] the difference from the last subpacket timestamp to the current one in time_base precission the lowwest bit is used to indicate if timestamp_diff_run[i] is coded timestamp_diff_run[i] the number of subpackets which have the same timestamp_diff if not coded than 1 0 is forbidden subpacket_size_diff the difference between the predicted size of this subpacket and the actual size the predicted size is 64 for the first subpacket in a packet otherwise it is MAX(64, last_subpacket_size) the size of the last subpacket is not coded and is simply the space left Note a subpacket MUST be in exactly one packet, it cannot be split msb_timestamp most significant bits of the timestamp, SHOULD be 0 for the first frame lsb_timestamp difference from the msb_timestamp in time_base precission Example: IBBP display order keyframe msb_timestamp=0 lsb_timestamp=0 -> timestamp=0 frame lsb_timestamp=3 -> timestamp=3 frame lsb_timestamp=1 -> timestamp=1 frame lsb_timestamp=2 -> timestamp=2 ... keyframe msb_timestamp=1 lsb_timestamp=1 -> timestamp=257 frame lsb_timestamp=-1-> timestamp=255 frame lsb_timestamp=0 -> timestamp=256 frame lsb_timestamp=4 -> timestamp=260 frame lsb_timestamp=2 -> timestamp=258 frame lsb_timestamp=3 -> timestamp=259 width/height MUST be set to the coded width/height sample_width/sample_height (aspect ratio) sample_width is the horizontal distance between samples sample_width and sample_height MUST be relative prime if not zero MUST be 0 if unknown depth for compatibility with some win32 codecs samplerate_mul the number of samples per second in one time_base unit samplerate = time_base*samplerate_mul zero_bit MUST be 0, its there to distinguish non keyframes from other packets, Note: all packets have a 64-bit startcode except non-keyframes to reduce their size, and all startcodes start with a 1 bit priority if 0 then the frame isnt used as reference (b frame) and can be droped MUST be > 0 for keyframes shuffle_type audio is often encoded in small subpackets, and to increase the error robustness these can be shuffled 0 -> no shuffle 1-16 -> interleave packets by 2^n checksum crc32 checksum using the generator polynomial 0x104c11db7 (same as ogg) checksum_flag indicates that the frame_checksum is coded must be 1 for the last non keyframe before a keyframe frame_checksum identical to checksum, but instead of covering just the current packet, it covers all frames of the same stream id since the last frame_checksum this field is only coded if checksum_flag=1 index_timestamp value in time_base precission, relative to the last index_timestamp index_position position in bytes of the first byte of the keyframe header, relative to the last index_position id the id of the type/name pair, so its more compact 0 means end type for example: "UTF8" -> String or "JPEG" -> jpeg image Note: nonstandard fields should be prefixed by "X-" Note: MUST be less than 6 byte long (might be increased to 64 later) name the name of the info entry, valid names are "StreamId" the stream(s) to which the info packet applies "StartTimestamp" "EndTimestamp" the time range in msecs to which the info applies "SegmentId" a unique id for the streams + time specified "Author" "Description" "Copyright" "Encoder" the name & version of the software used for encoding "Title" "Cover" an image of the (cd,dvd,vhs,..) cover (preferable PNG or JPEG) "Source" "DVD", "VCD", "CD", "MD", "FM radio", "VHS", "TV", "LD" Optional: appended PAL,NTSC,SECAM, ... in parentheses "CaptureDevice" "BT878", "BT848", "webcam", ... (more exact names are fine too) "CreationTime" "2003-01-20 20:13:15Z", ... (ISO 8601 format, see http://www.cl.cam.ac.uk/~mgk25/iso-time.html) Note: dont forget the timezone "Keywords" Note: if someone needs some others, please tell us about them, so we can add them to the official standard (if they are sane) Note: nonstandard fields should be prefixed by "X-" Note: MUST be less than 64 bytes long value value of this name/type pair stuffing 0x80 can be placed infront of any type v entry for stuffing purposes info_table[][2]={ {NULL , NULL }, // end {NULL , NULL }, {NULL , "UTF8"}, {NULL , "v"}, {NULL , "s"}, {"StreamId" , "v"}, {"SegmentId" , "v"}, {"StartTimestamp" , "v"}, {"EndTimestamp" , "v"}, {"Author" , "UTF8"}, {"Titel" , "UTF8"}, {"Description" , "UTF8"}, {"Copyright" , "UTF8"}, {"Encoder" , "UTF8"}, {"Keyword" , "UTF8"}, {"Cover" , "JPEG"}, {"Cover" , "PNG"}, }; Structure: the headers MUST be in exactly the following order (to simplify demuxer design) main header stream_header (id=0) stream_header (id=1) ... stream_header (id=n) headers may be repated, but if they are then they MUST all be repeated together and repeated headers MUST be identical headers MUST be repeated every 10sec at least ? FIXME headers MUST be repeated at least twice (so they exist 3 times in a file) Index the index can be repeated but there SHOULD be at least one for each stream at the end 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 Stuffing packets can be used as a filler, for example to leave some empty space at the begin for a copy of the index Unknown packets MUST be ignored by the decoder 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; ibuf_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(ByteStream *bc){ uint64_t val= 0; for(; spaceLeft(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(ByteStream *bc, uint64_t val){ int i; if(spaceLeft(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-=8){ *(bc->buf_ptr++)= 0x80 | (val>>i); } *(bc->buf_ptr++)= val&0x7F; return 0; } static inline int put_s(ByteStream *bc, uint64_t val){ if(val<=0) return put_v(bc, -2*val ); else return put_v(bc, 2*val-1); } static inline int64_t get_s(ByteStream *bc){ int64_t v= get_v(bc) + 1; if(v&1) return -(v>>1); else return (v>>1); } Example stream main header video_stream_header (stream 0, video jpjp, timebase 30, lsb_timestamp_length=8) video_stream_header (stream 1 subtitle usen, timebase 30, lsb_timestamp_length=8) video_stream_header (stream 2 subtitle atde, timebase 30, lsb_timestamp_length=8) audio_stream_header (stream 3, audio jpjp, timebase 1 , lsb_timestamp_length=8) audio_stream_header (stream 4, audio usen, timebase 1 , lsb_timestamp_length=8) index (stream 0) keyframe (stream 0, msb_timestamp=0, lsb_timestamp=0) keyframe (stream 1, msb_timestamp=0, lsb_timestamp=0) keyframe (stream 2, msb_timestamp=0, lsb_timestamp=0) keyframe (stream 3, msb_timestamp=0, lsb_timestamp=0) keyframe (stream 4, msb_timestamp=0, lsb_timestamp=0) frame (stream 0, lsb_timestamp=1) frame (stream 0, lsb_timestamp=2) ... frame (stream 0, lsb_timestamp=30) keyframe (stream 3, msb_timestamp=0, lsb_timestamp=1) keyframe (stream 4, msb_timestamp=0, lsb_timestamp=1) frame (stream 0, lsb_timestamp=31) frame (stream 0, lsb_timestamp=32) ... frame (stream 0, lsb_timestamp=60) frame (stream 1, lsb_timestamp=60) frame (stream 2, lsb_timestamp=60) keyframe (stream 3, msb_timestamp=0, lsb_timestamp=2) keyframe (stream 4, msb_timestamp=0, lsb_timestamp=2) frame (stream 0, lsb_timestamp=61) frame (stream 0, lsb_timestamp=62) ... main header video_stream_header (stream 0, video jpjp, timebase 30, lsb_timestamp_length=8) video_stream_header (stream 1 subtitle usen, timebase 30, lsb_timestamp_length=8) video_stream_header (stream 2 subtitle atde, timebase 30, lsb_timestamp_length=8) audio_stream_header (stream 3, audio jpjp, timebase 1 , lsb_timestamp_length=8) audio_stream_header (stream 4, audio usen, timebase 1 , lsb_timestamp_length=8) frame (stream 0, lsb_timestamp=255) frame (stream 0, msb_timestamp=1 lsb_timestamp=0) frame (stream 0, lsb_timestamp=1) frame (stream 0, lsb_timestamp=2) frame (stream 1, msb_timestamp=1 lsb_timestamp=2) frame (stream 2, msb_timestamp=1 lsb_timestamp=2) frame (stream 0, lsb_timestamp=3) frame (stream 0, lsb_timestamp=4) ... keyframe (stream 3, msb_timestamp=0, lsb_timestamp=9) keyframe (stream 4, msb_timestamp=0, lsb_timestamp=9) main header video_stream_header (stream 0, video jpjp, timebase 30, lsb_timestamp_length=8) video_stream_header (stream 1 subtitle usen, timebase 30, lsb_timestamp_length=8) video_stream_header (stream 2 subtitle atde, timebase 30, lsb_timestamp_length=8) audio_stream_header (stream 3, audio jpjp, timebase 1 , lsb_timestamp_length=8) audio_stream_header (stream 4, audio usen, timebase 1 , lsb_timestamp_length=8) index (stream 0)