[MPlayer-dev-eng] Lots of stuff for NUT
Luca Barbato
lu_zero at gentoo.org
Tue Jan 3 21:20:44 CET 2006
Oded Shimon wrote:
>
> Index: DOCS/tech/mpcf.txt
> ===================================================================
> RCS file: /cvsroot/mplayer/main/DOCS/tech/mpcf.txt,v
> retrieving revision 1.86
> diff -u -r1.86 mpcf.txt
> --- DOCS/tech/mpcf.txt 22 Dec 2005 05:48:04 -0000 1.86
> +++ DOCS/tech/mpcf.txt 3 Jan 2006 19:28:16 -0000
> @@ -1,5 +1,5 @@
> ========================================
> -NUT Open Container Format DRAFT 20051118
> +NUT Open Container Format DRAFT 20060103
> ========================================
>
>
> @@ -21,13 +21,13 @@
>
> Compact
> ~0.2% overhead, for normal bitrates
s/sec/s
> - index is <10kb per hour (1 keyframe every 3sec)
> + index is <100kb per hour (1 keyframe every 3sec)
> a usual header for a file is about 100 bytes (audio + video headers together)
> - a packet header is about ~1-8 bytes
> + a packet header is about ~1-5 bytes
>
> Error resistant
s:/:and
> seeking / playback without an index
> - headers & index can be repeated
> + headers can be repeated
> damaged files can be played back with minimal data loss and fast
> resync times
>
> @@ -134,26 +134,29 @@
> version v
> stream_count v
> max_distance v
> - max_index_distance v
> - global_time_base_nom v
> - global_time_base_denom v
> for(i=0; i<256; ){
> tmp_flag v
> tmp_fields v
> - if(tmp_fields>0) tmp_pts s
> - if(tmp_fields>1) tmp_mul v
> - if(tmp_fields>2) tmp_stream v
> - if(tmp_fields>3) tmp_size v
> + if(tmp_fields>0) tmp_mul v
> + else tmp_mul=1
> + if(tmp_fields>1) tmp_sflag v
> + else tmp_sflag=0
> + if(tmp_fields>2) tmp_pts s
> + else tmp_pts=0
> + if(tmp_fields>3) tmp_stream v
> + else tmp_stream=0
> + if(tmp_fields>4) tmp_size v
> else tmp_size=0
> - if(tmp_fields>4) tmp_res v
> + if(tmp_fields>5) tmp_res v
> else tmp_res=0
> - if(tmp_fields>5) count v
> + if(tmp_fields>6) count v
> else count= tmp_mul - tmp_size
> - for(j=6; j<tmp_fields; j++){
> + for(j=7; j<tmp_fields; j++){
> tmp_reserved[i] v
> }
> for(j=0; j<count && i<256; j++, i++){
> flags[i]= tmp_flag;
> + stream_flags[i]= tmp_sflag;
> stream_id_plus1[i]= tmp_stream;
> data_size_mul[i]= tmp_mul;
> data_size_lsb[i]= tmp_size + j;
> @@ -214,6 +217,9 @@
> if(flags[frame_code]&1){
> data_size_msb v
> }
> + if(flags[frame_code]&2){
> + coded_stream_flags v
> + }
> for(i=0; i<reserved_count[frame_code]; i++)
> reserved v
> data
> @@ -221,12 +227,36 @@
> index:
> index_startcode f(64)
> packet header
> - stream_id v
> max_pts v
> - index_length v
> - for(i=0; i<index_length; i++){
> - index_pts v
> - index_position v
> + syncpoints v
> + for(i=0; i<syncpoints; i++){
> + syncpoint_pos_div8 v
> + }
wordy description needed ^^;
> + for(i=0; i<stream_count; i++) {
> + j = 0
> + while (j < syncpoints) {
> + repeat v
> + type = repeat & 1
> + repeat = repeat >> 1
> + b = repeat & 1
> + repeat = (repeat >> 1) + 1
> + if (type) {
> + key_pts v
> + key_pts += syncpoint[j-1].stream[i].key_pts
> + for(k=0; k<repeat; k++) {
> + syncpoint[j+k].stream[i].back_ptr = syncpoint[j-b].pos_div8
> + syncpoint[j+k].stream[i].key_pts = key_pts
> + }
> + } else {
> + for(k=0; k<repeat; k++) {
> + syncpoint[j+k].stream[i].back_ptr = syncpoint[j+k-b].pos_div8
> + key_pts v
> + key_pts += syncpoint[j+k-1].stream[i].key_pts
> + syncpoint[j+k].stream[i].key_pts = key_pts
> + }
> + }
> + j += repeat
> + }
> }
> reserved_bytes
> checksum u(32)
> @@ -243,6 +273,8 @@
> name vb
> if(type=="v")
> value v
> + else if(type=="s")
> + value s
> else
> value vb
> }
> @@ -254,10 +286,26 @@
> packet header
> info_frame
>
> -sync_point:
> - frame_startcode f(64)
> - global_timestamp v
> - back_ptr v
> +syncpoint:
> + syncpoint_startcode f(64)
> + coded_pts v
> + stream = coded_pts % stream_count
> + back_ptr_div8[0] v
> + back_ptr[stream] = back_ptr_div8[0]
> + global_key_pts = coded_pts/stream_count
> + key_pts[stream] = global_key_pts
> + n=1
> + for (i=0; i<stream_count; i++) {
> + if (i == stream) continue
> + coded_pts v
> + A= coded_pts % (n+1)
> + B= coded_pts / (n+1)
> + if(A == n)
> + back_ptr_div8[n++] v
> + back_ptr[i]= back_ptr_div8[A]
> + key_pts[i] = covert_ts(global_key_pts, timebase[stream], timebase[i])
> + key_pts[i] -= B
> + }
>
> Complete definition:
>
> @@ -277,15 +325,13 @@
> info_packet
> }
> while(next_code != main_startcode){
> - if(next_code == frame_startcode)
> - sync_point
> + if(next_code == syncpoint_startcode)
> + syncpoint
> frame
> }
> }
> if (next_code == index_startcode){
> - while(!eof){
> - index
> - }
> + index
> index_ptr u(64)
> }
>
> @@ -297,12 +343,33 @@
> size of the packet data (exactly the distance from the first byte
> after the forward_ptr to the first byte of the next packet)
>
> -back_ptr
> +back_ptr[stream]
First tell what a back_ptr is, then what are the constraints and then
how to calculate the correct address.
> real_back_ptr = back_ptr * 8 + 7
> - real_back_ptr must point to a position such that a syncpoint
> - startcode begins within the next 8 bytes, and such that at least
> - one keyframe for each stream lies between the syncpoint to which
> - real_back_ptr points, and the current syncpoint.
> + real_back_ptr must point to a position within 8 bytes of a syncpoint
> + startcode. This syncpoint MUST be the closest syncpoint such that at
> + least one keyframe for this stream lies between it and the current
> + syncpoint, or immediately after the current syncpoint.
> +
Is End Of Relevance defined before?
> + Note: back_ptr can be zero, when the frame immediately following is
> + a keyframe of this stream, or EOR has been set for this stream.
> + back_ptr of a stream where EOR is set MUST be zero.
> +
> + Note: SOR is a keyframe like any other and back_ptr must point to it if
> + necessary.
> +
> +global_key_pts
> + After a syncpoint, last_pts of each stream is to be set to:
convert_ts isn't defined before I'd move it
> + last_pts[i] = convert_ts(global_key_pts, timebase[i], timebase[stream])
> +
> + To be able to code key_pts for every stream, global_key_pts MUST be the
> + max key_pts across all streams.
> +
> +key_pts[stream]
> + The pts of the last keyframe in the stream until the syncpoint
> + including the frame immediately following the syncpoint.
> +
> + Note: After an EOR, key_pts MUST be set to global_key_pts in correct
> + timebase. This is to be done by using coded_pts of 0.
>
> file_id_string
> "nut/multimedia container\0"
> @@ -316,13 +383,9 @@
> stream_starcode
> 0x11405BF2F9DBULL + (((uint64_t)('N'<<8) + 'S')<<48)
>
> -frame_startcode
> +syncpoint_startcode
> 0xE4ADEECA4569ULL + (((uint64_t)('N'<<8) + 'K')<<48)
>
> - frame_startcodes SHOULD be placed immediately before a keyframe if the
> - previous frame of the same stream was a non-keyframe, unless such
> - non-keyframe - keyframe transitions are very frequent
> -
> index_startcode
> 0xDD672F23E64EULL + (((uint64_t)('N'<<8) + 'X')<<48)
>
> @@ -333,22 +396,21 @@
> NUT version. The current value is 2.
>
> max_distance
> - max distance of frame_startcodes, the distance may only be larger if
> - there is only a single frame between the two frame_startcodes this can
> + max distance of syncpoints, the distance may only be larger if
> + there is no more than a single frame between the two syncpoints. This can
> be used by the demuxer to detect damaged frame headers if the damage
> results in too long of a chain
>
> + Syncpoints MUST be placed immediately before a non-EOR keyframe if the
> + back_ptr of this stream in the last syncpoint is greater than
> + max_distance.
> +
> + The begginning of a frame is defined by the first byte of the frame header.
> +
> SHOULD be set to <=32768 or at least <=65536 unless there is a very
> good reason to set it higher, otherwise reasonable error recovery will
> be impossible
>
> -max_index_distance
> - max distance of keyframes which are represented in the index, the
> - distance between consecutive entries A and B may only be larger if
> - there are no keyframes within this stream between A and B
> - SHOULD be set to <=32768 or at least <=65536 unless there is a very
> - good reason to set it higher
> -
> stream_id
> Stream identifier
> stream_id MUST be < stream_count
> @@ -381,22 +443,15 @@
> 29.97 1001 30000
> 23.976 1001 24000
>
> -global_time_base_nom / global_time_base_denom = global_time_base
> - the length of a timer tick in seconds
> - global_time_base_nom and global_time_base_denom MUST NOT be 0
> - global_time_base_nom and global_time_base_denom MUST be relatively prime
> - global_time_base_denom MUST be < 2^31
> -
> -global_timestamp
> - timestamp in global_time_base units
> - when a global_timestamp is encountered the last_pts of all
> - streams is set to the following:
> -
> - ln = global_time_base_nom*time_base_denom
> - sn = global_timestamp
> - d1 = global_time_base_denom
> - d2 = time_base_nom
> - last_pts = (ln/d1*sn + ln%d1*sn/d1)/d2
> +convert_ts
> + To switch from 2 different timebases, the following calculation is
> + defined:
> +
> + ln = from_time_base_nom*to_time_base_denom
> + sn = from_timestamp
> + d1 = from_time_base_denom
> + d2 = to_time_base_nom
> + timestamp = (ln/d1*sn + ln%d1*sn/d1)/d2
> Note: this calculation MUST be done with unsigned 64 bit integers, and
> is equivalent to (ln*sn)/(d1*d2) but this would require a 96bit integer
>
> @@ -422,17 +477,32 @@
> different from the first byte of any startcode
>
> flags[frame_code]
> - first of the flags from MSB to LSB are called KD
> - if D is 1 then data_size_msb is coded, otherwise data_size_msb is 0
> - K is the keyframe_type
> - 0 -> no keyframe,
> - 1 -> keyframe,
> - flags=4 can be used to mark illegal frame_code bytes
> - frame_code=78 must have flags=4
> - Note: frames MUST NOT depend(1) upon frames prior to the last
> - frame_startcode
> - Important: depend(1) means dependency on the container level (NUT) not
> - dependency on the codec level
> + Bit Name Description
> + 1 data_size_msb if set, data_size_msb is at frame header,
> + otherwise data_size_msb is 0
> + 2 more_flags if set, stream control flags are at frame header.
> + 4 invalid if set, frame_code is invalid.
> +
> + frame_code=78 ('N') MUST have flags=64
> +
> +stream_flags
> + stream_flags is "stream_flags[frame_code] | coded_stream_flags"
> +
> + Bit Name Description
> + 1 is_key if set, frame is keyframe
> + 2 end_of_relevance if set, stream has no relevance on
> + presentation. (EOR)
> + 4 start_of_relevance if set, unsets EOR. (SOR)
> +
> + EOR and SOR frames MUST be zero-length and must be set keyframe.
> + All streams SHOULD end with EOR, where the pts of the EOR indicates the
> + end presentation time of the final frame.
> + An EOR set stream MUST be unset by an SOR before any content frames.
> + An SOR sets the dts_cache of the stream to the pts of of the SOR.
> + The dts of an SOR is its pts. SOR pts MUST be smaller to pts of all
> + subsequent frames on this stream.
> + Note: SOR can and SHOULD immediately precede the first content frame
> + of its stream.
>
> stream_id_plus1[frame_code]
> must be <250
> @@ -479,9 +549,10 @@
> stream, into which the current pts is inserted and the element with
> the smallest value is removed, this is then the current dts
> this buffer is initalized with decode_delay -1 elements
> - all frames must be monotone, that means a frame
> - which occurs later in the stream must have a larger or equal dts
> - than an earlier frame
> +
> + Pts of all frames in all streams MUST be bigger or equal to dts of all
> + previous frames in all streams, compared in common timebase. (SOR and
> + EOR frames are NOT exempt from this rule)
>
> width/height
> MUST be set to the coded width/height
> @@ -508,23 +579,22 @@
> forward_ptr until last byte before the checksum).
>
> max_pts
> - The highest pts in the stream.
> -
> -index_pts
> - value of the pts of a keyframe relative to the last keyframe
> - stored in this index
> -
> -index_position
> - position in bytes of the first byte of a keyframe, relative to the
> - last keyframe stored in this index
> - there MUST be no keyframe with the same stream_id as this index between
> - two consecutive index entries if they are more than max_index_distance
> - apart
> + s = max_pts % stream_count
> + pts = max_pts / stream_count
> + The highest pts in the entire file in the timebase of stream 's'.
> +
> +syncpoints
> + amount of syncpoints in the file.
> +
> +syncpoint_pos_div8
> + offset from begginning of file to up to 7 bytes before the syncpoint
> + referred to in this index entry. Relative to position of last
> + syncpoint.
>
> index_ptr
> - Length in bytes from the first byte of the first index startcode
> - to the first byte of the index_ptr. If there is no index, index_ptr
> - MUST NOT be written.
> + Length in bytes from the first byte of the index startcode to the first
> + byte of the index_ptr. If there is no index, index_ptr MUST NOT be
> + written.
>
> id
> the ID of the type/name pair, so it is more compact
>
Looks ok, with just some minor changes and maybe a paragraph to explain
back pointers, relevance, etc.
lu
--
Luca Barbato
Gentoo/linux Developer Gentoo/PPC Operational Leader
http://dev.gentoo.org/~lu_zero
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