about WMA audio stream, what does "Codec Specific Data" mean
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about WMA audio stream, what does "Codec Specific Data" mean

 
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dspshin
Guest
Posted: Fri Sep 17, 2004 12:00 pm    Post subject: about WMA audio stream, what does "Codec Specific Data" mean Reply with quote
below is parsed information by windows media asf view 9 series program
=======================================================================
Stream Properties Object [1] (114 bytes)
=======================================================================

Property Value
-----------------------------------------------------------------------
File Position || 2162 ( 0x872 )
Object ID || B7DC0791-A9B7-11CF-8EE6-00C00C205365
Object Size || 114 ( 0x72 )
-----------------------------------------------------------------------
Stream Number || 1
Version || 1
Offset || 0
Encrypted || False
Security ID || 421789336 ( 0x1923FE98 )
----------------------------------------------------------------------
Stream Type Specific
----------------------------------------------------------------------
Stream Type || Audio Media
Format Tag || 353
Channels || 2
Samples / Seconds || 48000
Average Bytes / Second || 16018
Average Bitrate (bits/sec) || 128144
Block Align || 5462 ( 0x1556 )
Bits / Sample || 16
Extra Data Size || 10
Extra Data 0000: || 00 88 00 00 0F 00 59 55-00 00
=======================================================================

i can understand upper information but i can't understand exactly
about Extra Data

in "Advanced Systems Format (ASF) Specification Document"
Extra Data is explained ....Codec Specific Data Specifies an array of
codec-specific data bytes...

i guess that Extra Data is

typedef struct {
WAVEFORMATEX Format;
~~~~~~~~~~~~~~ Extra Data start ----> ~~~~~
union {
WORD wValidBitsPerSample;
WORD wSamplesPerBlock;
WORD wReserved;
} Samples;
DWORD dwChannelMask;
GUID SubFormat;
<---------- Extra Data end ~~~~~~~~~~~~~

} WAVEFORMATEXTENSIBLE, *PWAVEFORMATEXTENSIBLE;

but actully does not matched between Extra Data and (00 88)(00 00)(0F
00)(59 55-00 00)
wValidBitsPerSample .........??
wSamplesPerBlock; .........??
wReserved; .........??
dwChannelMask..??
is there any one who explain about Extra Data or "Codec Specific Data"
in ASF file format(about wma audio stream)..

thank for your regard...

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Alessandro Angeli [MVP::D
Guest
Posted: Fri Sep 17, 2004 1:01 pm    Post subject: Re: about WMA audio stream, what does "Codec Specific Data" Reply with quote
"dspshin" <dspshin@mediaworks.co.kr> wrote:

Quote:
is there any one who explain about Extra Data or "Codec Specific Data"
in ASF file format(about wma audio stream)..

The Codec Specific Data used by the WMA codec is undocumented: as the naming
suggests, it is data only the codec knows about and is completely opaque
unless you have specific information about the codec (and none is available
about the WMA codec).


--

Alessandro Angeli

MVP::DigitalMedia

a dot angeli at biosys dot net
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