RepoMirrors
/
mpv
mirror of https://github.com/mpv-player/mpv
1
0
Fork 0
Code Issues Releases Wiki Activity

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...


git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@16430 b3059339-0415-0410-9bf9-f77b7e298cf2
This commit is contained in:
ods15 2005-09-09 10:26:21 +00:00
parent e548b29dd0
commit a93326ef44
1 changed files with 87 additions and 71 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

158
DOCS/tech/mpcf.txt
View File

@ -1,4 +1,4 @@
NUT Open Container Format DRAFT 20050111
NUT Open Container Format DRAFT 20050909
----------------------------------------
@ -125,7 +125,7 @@ main header:
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 @@ main header:
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_header:
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 @@ audio_stream_header:
reserved_bytes
checksum u(32)
other_stream_header:
stream_header
reserved_bytes
checksum u(32)
Basic Packets:
frame:
@ -189,8 +193,8 @@ frame:
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:
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 @@ file:
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 @@ file:
}
}
}
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 @@ max_index_distance
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 @@ fourcc
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_mul[frame_code]
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 @@ dts
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 @@ samplerate_nom / samplerate_denom = samplerate
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 @@ index_position
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 @@ headers MUST be placed at least at the start of the file and immediately before
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 @@ in the absence of a valid header at the beginning, players SHOULD search for
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 @@ Authors in alphabetical order: (FIXME! Tell us if we left you out)
Gereoffy, Arpad (arpi@thot.banki.hu)
Hess, Andreas (jaska@gmx.net)
Niedermayer, Michael (michaelni@gmx.at)
Shimon, Oded (ods15@ods15.dyndns.org)