[MPlayer-cvslog] CVS: main/DOCS/tech mpcf.txt,1.73,1.74
Oded Shimon CVS
syncmail at mplayerhq.hu
Fri Sep 9 12:26:24 CEST 2005
CVS change done by Oded Shimon CVS
Update of /cvsroot/mplayer/main/DOCS/tech
In directory mail:/var2/tmp/cvs-serv4539
Modified Files:
mpcf.txt
Log Message:
Updates to NUT spec:
1. remove average_bitrate
2. add other_stream_header, for subtitles and metadata
3. add max_pts to index
4. index_ptr - a 64 bit integer to say the total length of all index packets
5. specify how to write "multiple" indexes
6. change forward_ptr behavior, starts right after forward_ptr, ends after
checksum
7. remove stream_id <-> stream_class limitation.
8. time_base_nom must also be non zero.
9. rename time_base_nom and time_base_denom, now timebase means the length
of a tick, not amounts of ticks
10. remove (old?) sample_rate_mul stuff.
11. specify what exactly the checksum covers.
12. specify that stream classes which have multiple streams must have an
info packet.. (in new Semantic requirements section)
13. Rename 'timestamp' to pts.
14. Change date of draft...
15. Add myself to authors...
Index: mpcf.txt
===================================================================
RCS file: /cvsroot/mplayer/main/DOCS/tech/mpcf.txt,v
retrieving revision 1.73
retrieving revision 1.74
diff -u -r1.73 -r1.74
--- mpcf.txt 9 Sep 2005 09:25:07 -0000 1.73
+++ mpcf.txt 9 Sep 2005 10:26:21 -0000 1.74
@@ -1,4 +1,4 @@
- NUT Open Container Format DRAFT 20050111
+ NUT Open Container Format DRAFT 20050909
----------------------------------------
@@ -125,7 +125,7 @@
for(i=0; i<256; ){
tmp_flag v
tmp_fields v
- if(tmp_fields>0) tmp_timestamp s
+ 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
@@ -142,7 +142,7 @@
stream_id_plus1[i]= tmp_stream;
data_size_mul[i]= tmp_mul;
data_size_lsb[i]= tmp_size + j;
- timestamp_delta[i]= tmp_timestamp;
+ pts_delta[i]= tmp_pts;
reserved_count[i]= tmp_res;
}
}
@@ -155,10 +155,9 @@
stream_id v
stream_class v
fourcc vb
- average_bitrate v
time_base_nom v
time_base_denom v
- msb_timestamp_shift v
+ msb_pts_shift v
decode_delay v
fixed_fps u(1)
reserved u(6)
@@ -182,6 +181,11 @@
reserved_bytes
checksum u(32)
+other_stream_header:
+ stream_header
+ reserved_bytes
+ checksum u(32)
+
Basic Packets:
frame:
@@ -189,8 +193,8 @@
if(stream_id_plus1[frame_code]==0){
stream_id v
}
- if(timestamp_delta[frame_code]==0){
- coded_timestamp v
+ if(pts_delta[frame_code]==0){
+ coded_pts v
}
if(flags[frame_code]&1){
data_size_msb v
@@ -203,9 +207,10 @@
index_startcode f(64)
packet header
stream_id v
+ max_pts v
index_length v
for(i=0; i<index_length; i++){
- index_timestamp v
+ index_pts v
index_position v
}
reserved_bytes
@@ -244,8 +249,10 @@
for(i=0; i<stream_count; i++){
if(next_packet==video_stream_header)
video_stream_header
- else
+ else if(next_packet==audio_stream_header)
audio_stream_header
+ else
+ other_stream_header
}
while(next_code != main_startcode){
if(next_code == info_startcode)
@@ -257,16 +264,19 @@
}
}
}
- index
-
+ if (next_code == index_startcode){
+ while(!eof){
+ index
+ }
+ index_ptr u(64)
+ }
Tag description:
forward_ptr
- size of the packet (exactly the distance from the first byte of the
- startcode of the current packet to the first byte of the following
- packet
+ size of the packet data (exactly the distance from the first byte
+ after the forward_ptr to the first byte of the next packet)
file_id_string
"nut/multimedia container\0"
@@ -312,11 +322,8 @@
SHOULD be set to <=32768 or at least <=65536 unless there is a very
good reason to set it higher
-stream_id[FIXME]
+stream_id
Stream identifier
- Note: streams with a lower relative class MUST have a lower relative ID
- so a stream with class 0 MUST always have an ID which is lower than any
- stream with class > 0
stream_id MUST be < stream_count
stream_class
@@ -334,45 +341,38 @@
if needed
time_base_nom / time_base_denom = time_base
- the number of timer ticks per second, this MUST be equal to the fps
+ the length of a timer tick in seconds, this MUST be equal to the 1/fps
if fixed_fps is 1
- time_base_denom MUST NOT be 0
+ time_base_nom and time_base_denom MUST NOT be 0
time_base_nom and time_base_denom MUST be relatively prime
- time_base_nom MUST be < 2^31
+ time_base_denom MUST be < 2^31
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
+ 30 1 30
+ 29.97 1001 30000
+ 23.976 1001 24000
global_time_base_nom / global_time_base_denom = global_time_base
- the number of timer ticks per second
- global_time_base_denom MUST NOT be 0
+ 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_nom MUST be < 2^31
+ global_time_base_denom MUST be < 2^31
global_timestamp
timestamp in global_time_base units
- when a global_timestamp is encountered the last_timestamp of all
+ when a global_timestamp is encountered the last_pts of all
streams is set to the following:
- ln= global_time_base_denom*time_base_nom
+ ln= global_time_base_nom*time_base_denom
sn= global_timestamp
- d1= global_time_base_nom
- d2= time_base_denom
- last_timestamp= (ln/d1*sn + ln%d1*sn/d1)/d2
+ d1= global_time_base_denom
+ d2= time_base_nom
+ last_pts= (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
-msb_timestamp_shift
- amount of bits in lsb_timestamp
+msb_pts_shift
+ amount of bits in lsb_pts
MUST be <16
decode_delay
@@ -415,37 +415,35 @@
data_size_lsb[frame_code]
must be <16384
-timestamp_delta[frame_code]
+pts_delta[frame_code]
must be <16384 and >-16384
data_size
data_size= data_size_lsb + data_size_msb*data_size_mul;
-coded_timestamp
- if coded_timestamp < (1<<msb_timestamp_shift) then it is an lsb
- timestamp, otherwise it is a full timestamp + (1<<msb_timestamp_shift)
- lsb timestamps are converted to full timesamps by:
- mask = (1<<msb_timestamp_shift)-1;
- delta= last_timestamp - mask/2
- timestamp= ((timestamp_lsb-delta)&mask) + delta
- a full timestamp MUST be used if there is no reference timestamp
- available after the last frame_startcode with the current stream_id
+coded_pts
+ if coded_pts < (1<<msb_pts_shift) then it is an lsb
+ pts, otherwise it is a full pts + (1<<msb_pts_shift)
+ lsb pts is converted to a full pts by:
+ mask = (1<<msb_pts_shift)-1;
+ delta= last_pts - mask/2
+ pts= ((pts_lsb-delta)&mask) + delta
-lsb_timestamp
- least significant bits of the timestamp in time_base precision
+lsb_pts
+ least significant bits of the pts in time_base precision
Example: IBBP display order
- keyframe timestamp=0 -> timestamp=0
- frame lsb_timestamp=3 -> timestamp=3
- frame lsb_timestamp=1 -> timestamp=1
- frame lsb_timestamp=2 -> timestamp=2
+ keyframe pts=0 -> pts=0
+ frame lsb_pts=3 -> pts=3
+ frame lsb_pts=1 -> pts=1
+ frame lsb_pts=2 -> pts=2
...
- keyframe msb_timestamp=257 -> timestamp=257
- frame lsb_timestamp=255->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
- all timestamps of keyframes of a single stream MUST be monotone
+ keyframe msb_pts=257 -> pts=257
+ frame lsb_pts=255->pts=255
+ frame lsb_pts=0 -> pts=256
+ frame lsb_pts=4 -> pts=260
+ frame lsb_pts=2 -> pts=258
+ frame lsb_pts=3 -> pts=259
+ all pts's of keyframes of a single stream MUST be monotone
dts
dts is calculated by using a decode_delay+1 sized buffer for each
@@ -455,7 +453,6 @@
all frames with dts == timestamp must be monotone, that means a frame
which occurs later in the stream must have a larger or equal dts
than an earlier frame
- FIXME rename timestamp* to pts* ?
width/height
MUST be set to the coded width/height
@@ -477,9 +474,15 @@
checksum
adler32 checksum
+ checksum is calculated for the area pointed to by forward_ptr not
+ including the checksum itself (from first byte after the
+ forward_ptr until last byte before the checksum).
-index_timestamp
- value of the timestamp of a keyframe relative to the last keyframe
+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
@@ -489,6 +492,11 @@
two consecutive index entries if they are more than max_index_distance
apart
+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.
+
id
the ID of the type/name pair, so it is more compact
0 means end
@@ -572,15 +580,13 @@
the index or at the file end if there is no index
headers MUST be repeated at least twice (so they exist three times in a file)
-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: with realtime streaming, there is no end, so no index there either
+An index SHOULD be written for every stream. Indices MUST be placed at end
+of file. Indices MAY be repeated for a stream.
Info packets
the info_packet can be repeated, and can also contain different names & values
@@ -600,6 +606,15 @@
backup headers starting at offset 2^x; for each x players SHOULD end their
search at a particular offset when any startcode is found (including syncpoint)
+ Semantic requirements
+
+If more than one stream of a given stream class is present, each one MUST
+have info tags specifying disposition, and if applicable, language.
+
+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.
+
Sample code (GPL, & untested)
@@ -691,3 +706,4 @@
Gereoffy, Arpad (arpi at thot.banki.hu)
Hess, Andreas (jaska at gmx.net)
Niedermayer, Michael (michaelni at gmx.at)
+ Shimon, Oded (ods15 at ods15.dyndns.org)
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