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git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@21191 b3059339-0415-0410-9bf9-f77b7e298cf2
This commit is contained in:
ivo
2006-11-24 16:31:48 +00:00
parent 4e4c540669
commit bd2cb0bb06
1 changed files with 44 additions and 44 deletions
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DOCS/tech/nut.txt
+44 -44
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@@ -410,42 +410,42 @@ file_id_string
the very first thing in every nut file, useful for identifying nut
files
*_startcode
*_startcode (f(64))
all startcodes start with 'N'
main_startcode
main_startcode (f(64))
0x7A561F5F04ADULL + (((uint64_t)('N'<<8) + 'M')<<48)
stream_startcode
stream_startcode (f(64))
0x11405BF2F9DBULL + (((uint64_t)('N'<<8) + 'S')<<48)
syncpoint_startcode
syncpoint_startcode (f(64))
0xE4ADEECA4569ULL + (((uint64_t)('N'<<8) + 'K')<<48)
index_startcode
index_startcode (f(64))
0xDD672F23E64EULL + (((uint64_t)('N'<<8) + 'X')<<48)
info_startcode
info_startcode (f(64))
0xAB68B596BA78ULL + (((uint64_t)('N'<<8) + 'I')<<48)
version
version (v)
NUT version. The current value is 3. All lower values are pre-freeze
stream_count
stream_count (v)
number of streams in this file
time_base_count
time_base_count (v)
number of different time bases in this file
this MUST NOT be 0
forward_ptr
forward_ptr (v)
size of the packet data (exactly the distance from the first byte
after the packet_header to the first byte of the next packet)
every nut packet contains a forward_ptr immediately after its startcode
with the exception of frame_code based packets, the forward pointer
can be used to skip over the packet without decoding its contents
max_distance
max_distance (v)
max distance between startcodes. If p1 and p2 are the byte
positions of the first byte of two consecutive startcodes, then
p2-p1 MUST be less than or equal to max_distance unless the entire
@@ -466,7 +466,7 @@ max_distance
frameheader.
max_pts_distance
max_pts_distance (v)
max absolute difference of pts of new frame from last_pts in the
timebase of the stream, without a checksum after the frameheader.
A frame header MUST include a checksum if abs(pts-last_pts) is
@@ -475,11 +475,11 @@ max_pts_distance
on the same stream, as it is altered by syncpoint timestamps.
SHOULD NOT be higher than 1/timebase
stream_id
stream_id (v)
Stream identifier
stream_id MUST be < stream_count
stream_class
stream_class (v)
0 video
1 audio
2 subtitles
@@ -487,7 +487,7 @@ stream_class
Note: the remaining values are reserved and MUST NOT be used
a demuxer MUST ignore streams with reserved classes
fourcc
fourcc (vb)
identification for the codec
example: "H264"
MUST contain 2 or 4 bytes, note, this might be increased in the future
@@ -495,7 +495,7 @@ fourcc
the id values used are the same as in avi, so if a codec uses a specific
fourcc in avi then the same fourcc MUST be used here
time_base_nom / time_base_denom = time_base
time_base_nom (v) / time_base_denom (v) = time_base
the length of a timer tick in seconds, this MUST be equal to the 1/fps
if FLAG_FIXED_FPS is set
time_base_nom and time_base_denom MUST NOT be 0
@@ -509,7 +509,7 @@ time_base_nom / time_base_denom = time_base
There MUST NOT be 2 identical timebases in a file.
There SHOULD NOT be more timebases than streams.
time_base_id
time_base_id (v)
index into the time_base table
MUST be < time_base_count
@@ -543,11 +543,11 @@ compare_ts
if (convert_ts(b, b_timebase, a_timebase) < a) return 1;
return 0;
msb_pts_shift
msb_pts_shift (v)
amount of bits in lsb_pts
MUST be <16
decode_delay
decode_delay (v)
size of the reordering buffer used to convert pts to dts
codecs which don't support b frames normally use 0
mpeg1/mpeg2 style codecs with b frames use 1
@@ -557,11 +557,11 @@ decode_delay
but its theoretically possible that one exists which needs it >0)
decode_delay MUST NOT be set higher than necessary for a codec.
stream_flags
stream_flags (v)
Bit Name Description
1 FLAG_FIXED_FPS indicates that the fps is fixed
codec_specific_data
codec_specific_data (vb)
private global data for a codec (could be huffman tables or ...)
if a codec has a global header it SHOULD be placed in here instead of
at the start of every keyframe
@@ -576,7 +576,7 @@ codec_specific_data
the encoder name and version, shall be considered essential as it is very
usefull to workaround possible encoder bugs
frame_code
frame_code (f(8))
frame_code is an 8-bit field which exists before every frame, it can
store part of the size of the frame, the stream number, the timestamp
and some flags amongst other things, what is not directly stored
@@ -587,7 +587,7 @@ frame_code
a muxer SHOULD mark 0x00 and 0xFF as invalid to improve error
detection
flags[frame_code], frame_flags
flags[frame_code], frame_flags (v)
Bit Name Description
1 FLAG_KEY if set, frame is keyframe
2 FLAG_EOR if set, stream has no relevance on
@@ -616,39 +616,39 @@ last_pts
if there is no such frame between the last syncpoint and the current
frame then the syncpoint timestamp is used, see global_key_pts
stream_id[frame_code]
stream_id[frame_code] (v)
if FLAG_STREAM_ID is not set then this is the stream number for the
frame following this frame_code
if FLAG_STREAM_ID is set then this value has no meaning
MUST be <250
data_size_mul[frame_code]
data_size_mul[frame_code] (v)
if FLAG_SIZE_MSB is set then data_size_msb which is stored after the
frame code is multiplied with it and forms the more significant part
of the size of the following frame
if FLAG_SIZE_MSB is not set then this field has no meaning
MUST be <16384
data_size_lsb[frame_code]
data_size_lsb[frame_code] (v)
the less significant part of the size of the following frame
this added together with data_size_mul*data_size_msb is the size of
the following frame
MUST be <16384
pts_delta[frame_code]
pts_delta[frame_code] (s)
MUST be <16384 and >-16384
if FLAG_CODED_PTS is set in the flags of the current frame then this
value MUST be ignored, if FLAG_CODED_PTS is not set then pts_delta is the
difference between the current pts and last_pts
reserved_count[frame_code]
reserved_count[frame_code] (v)
MUST be <256
data_size
the size of the following frame
data_size= data_size_lsb + data_size_msb*data_size_mul;
coded_pts
coded_pts (v)
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:
@@ -689,29 +689,29 @@ dts
Dts of all frames MUST be bigger or equal to dts of all previous frames
in the same stream
width/height
width (v) / height (v)
width and height of the video in pixels
MUST be set to the coded width/height, MUST NOT be 0
sample_width/sample_height (aspect ratio)
sample_width (v) /sample_height (v) (aspect ratio)
sample_width is the horizontal distance between samples
sample_width and sample_height MUST be relatively prime if not zero
both MUST be 0 if unknown otherwise both MUST be non zero
colorspace_type
colorspace_type (v)
0 unknown
1 ITU Rec 624 / ITU Rec 601 Y range: 16..235 Cb/Cr range: 16..240
2 ITU Rec 709 Y range: 16..235 Cb/Cr range: 16..240
17 ITU Rec 624 / ITU Rec 601 Y range: 0..255 Cb/Cr range: 0..255
18 ITU Rec 709 Y range: 0..255 Cb/Cr range: 0..255
samplerate_nom / samplerate_denom = samplerate
samplerate_nom (v) / samplerate_denom (v) = samplerate
the number of samples per second, MUST NOT be 0
crc32 checksum
Generator polynomial is 0x104C11DB7. Starting value is zero.
checksum
checksum (u(32))
crc32 checksum
checksum is calculated for the area pointed to by forward_ptr not
including the checksum itself (from first byte after the
@@ -719,13 +719,13 @@ checksum
for frame headers the checksum contains the framecode byte and all
following bytes up to the checksum itself
header_checksum
header_checksum (u(32))
checksum over the startcode and forward pointer
Syncpoint tags:
---------------
back_ptr_div16
back_ptr_div16 (v)
back_ptr = back_ptr_div16 * 16 + 15
back_ptr must point to a position within 16 bytes of a syncpoint
startcode. This syncpoint MUST be the closest syncpoint such that at
@@ -734,7 +734,7 @@ back_ptr_div16
A stream where EOR is set is to be ignored for back_ptr.
global_key_pts
global_key_pts (t)
After a syncpoint, last_pts of each stream is to be set to:
last_pts[i] = convert_ts(global_key_pts, time_base[id], time_base[i])
@@ -744,10 +744,10 @@ global_key_pts
Index tags:
-----------
max_pts
max_pts (t)
The highest pts in the entire file
syncpoint_pos_div16
syncpoint_pos_div16 (v)
offset from beginning of file to up to 15 bytes before the syncpoint
referred to in this index entry. Relative to position of last
syncpoint.
@@ -764,7 +764,7 @@ eor_pts
Coded only if EOR is set at the position of the syncpoint. The pts of
that EOR. EOR is unset by the first keyframe after it.
index_ptr
index_ptr (u(64))
Length in bytes of the entire index, from the first byte of the
startcode until the last byte of the checksum.
Note: A demuxer can use this to find the index when it is written at
@@ -775,11 +775,11 @@ index_ptr
Info tags:
----------
stream_id_plus1
stream_id_plus1 (v)
Stream this info packet applies to. If zero, packet applies to whole
file.
chapter_id
chapter_id (s)
Id of chapter this packet applies to. If zero, packet applies to whole
file. Positive chapter_id's are real chapters and MUST NOT overlap.
Negative chapter_id indicate a sub region of file and not a real
@@ -787,10 +787,10 @@ chapter_id
chapter_id n MUST not be used unless there are at least n chapters in the
file
chapter_start
chapter_start (t)
timestamp of start of chapter
chapter_len
chapter_len (v)
Length of chapter in same timebase of chapter_start.
type