??,?: [Mp4-tech] iso base media file format

[tim huang]

aligned(8) class Box (unsigned int(32) boxtype, optional unsigned
int(8)[16] extended_type) 
{
 unsigned int(32) size; 
 unsigned int(32) type = boxtype; 
if (size==1) 
{ unsigned int(64) largesize; 
} else if (size==0) 
{ // box extends to end of file } 
if (boxtype== uuid ) 
{ unsigned int(8)[16] usertype = extended_type; }
 }
the above infomation mean that:
in the file,the bit stream is structured with
32bit 32bit
size  boxtype 
if size's value equal with 1,and follow bit stream is
64bit
largesize
also follow bit stream is sixteen 8bit's extended_type.
and the bit stream is structured with network bit order.
my english is poor,sorry.
tim huang
2024.4.22
-----????-----
???: mp4-tech-bounces lists.mpegif.org
[mailto:mp4-tech-bounces lists.mpegif.org]?? Rajorshi Biswas
????: 2004?4?20? 13:03
???: mp4-tech lists.mpegif.org
??: [Mp4-tech] iso base media file format
Hi,
	This is my first mail to this list. First let me introduce
myself: I am a student graduating in Information Science. I am
working on a project involving 3gpp and 3gpp2 stuff. 
And I need help!
	Currently my job is this : I have a .3gp or .3gp2 file. From
this file, I have to find out several characteristics, such as:
1. duration, frame-rate, resolution of the h263 or mpeg-4 video.
2. duration,bit-rate of amr audio.
3. info of QCELP audio, 3gtext etc.
	I found out from the 3gpp documentation for the .3gp file
format that the file format is a derivative of the ISO base
media file format (which is why just the .3gp format description
was not making much sense), just like mpeg-4. 
I (after much effort) found a copy of the ISO base media 
file format specification.
	Unfortunately, it seems that this format is quite complex
to understand. Moreover in the very beginning, it refers to the
"Syntax Description Language" defined in MPEG-4 standard. And
I just cannot afford the MPEG-4 standard from iso.ch
	Basically I need help in any one of the following:
1. Understanding the Syntax Description Language
   eg. what does this mean :
aligned(8) class Box (unsigned int(32) boxtype, optional unsigned
int(8)[16] extended_type) 
{
 unsigned int(32) size; 
 unsigned int(32) type = boxtype; 
if (size==1) 
{ unsigned int(64) largesize; 
} else if (size==0) 
{ // box extends to end of file } 
if (boxtype== uuid ) 
{ unsigned int(8)[16] usertype = extended_type; }
 }
2. Understanding how to parse a format that is 
a derivative of iso base media file format
(mpeg-4 or .3gp or .3gp2). I cant understand
how to parse the boxes at all.
	Please, please help me or point me
to relevant information.
	Thanks a lot in advance.
Rajorshi 
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