[asterisk-users] file command with alaw file

[Pham Quy]

On Mon, 2010-05-17 at 13:06 +0700, Pham Quy wrote:
> hi all,
> 
> I install Asterisk 1.6 on Centos 5.2 (kernel 2.6.18-92.el5 #1 SMP Tue
> Jun 10 18:51:06 EDT 2008 x86_64 x86_64 x86_64 GNU/Linux) and do record
> audio clip with mixmonitor() as alaw file (softphone is also configured
> with alaw active only). Using file command i can get the following
> information
> 
> 983006584-20100517-125002.alaw: RIFF (little-endian) data, WAVE audio,
> ITU G.711 A-law, mono 8000 Hz
> 
> But when i install the same system on Centos 5.5 (kernel 2.6.18-92.el5
> #1 SMP Tue Jun 10 18:51:06 EDT 2008 x86_64 x86_64 x86_64 GNU/Linux) i
> could get the same information with file command. File command
> recognized alaw file as JPEG image:
> 
> 983006584-20100517-123825.alaw: JPEG image data
> 
> I guess i may miss something when i setup the new on on Centos 5.5, but
> u dont know what it is. Anyone have idea about this?
> 
> please help.
> 
> Thanks in advance.
> Quyps

I did check content of two alaw files (using a hex editor) generated
from two aboves cases. For the one fromo CentOS 5.2, beginning bytes
look likes : 

RIFF1^0.WAVEfmt........ at ...@.......fact.....^0.data.^0...

and the one from CentOS 5.5 

......................RQVTV........XEMBAX............

It seem like the first one have some information about file format,
which make our convert tool works correctly, and which the second one
doesnt have.

Can you explain to me this different, and how can i get the information
as the first one?

Thanks in advances,
Quyps