[asterisk-users] file command with alaw file
Pham Quy
quyps at vega.com.vn
Thu May 20 02:49:55 CDT 2010
Hi,
How can I convert FROM ALAW file, which generated by asterisk apps
(monitor, or record app), to format (wav or mp3) that is playable by
music player?? Can Sox do this?
I have an asterisk 1.6.2.6 on my CentOS 5.2. I record audio clip by
mixmonitor app and use file command to check the alaw output, and here
is output:
---------
983006584-20100517-125002.alaw: RIFF (little-endian) data, WAVE audio,
ITU G.711 A-law, mono 8000 Hz
---------
How could file command recognize the format as there is no header in the
output file? Or Did I probably miss something making asterisk yield
incorrect alaw files?
Please help, thanks
Quyps
On Thu, 2010-05-20 at 00:50 -0600, Steve Murphy wrote:
> Quyps--
>
> I've noticed in general that the ulaw, alaw, gsm, slin files used and
> generated by
> asterisk do not have headers (the RIFF stuff), and asterisk is not
> expecting them. in general they
> will louse up Asterisk's ability to play the sound. They are just raw
> data and the extension
> on the file name (.gsm, or .ulaw, etc) is the only clue to the file
> format/contents.
>
> In general, if you need a sound file of your own making in a certain
> format, you can convert
> to most of the formats using sox in linux, but really, the best thing
> to do is record the source
> sound file in cd-quality sound WAV format, in 44 khz sampling rate, or
> higher, and then
> use sox to convert to 8khz format. Asterisk can do some of this via
> the file convert CLI
> command, ( on the asterisk cli, type "help file convert"). You'd have
> to judge for yourself
> if "file convert tt-weasels.gsm tt-weasels.ulaw" which would convert
> the 8khz gsm format to
> 8 khz ulaw, or "sox -v 0.7 tt-weasels.44khz.wav -r 8000 -c 1 -t sw
> tt-weasels.raw;"
> "sox -r 8000 -c 1 -t sw tt-weasels.raw -t ul tt-weasels.ulaw" which
> is the way the Asterisk
> sounds are produced from the the cd-quality sounds. They would seem a
> bit equivalent.
>
> I wonder if just "sox -v 0.7 tt-weasels.44khz.wav -r 8000 -c 1 -t ul
> tt-weasels.ulaw" would
> sound any better... you audio engineers out there may have an opinion.
>
> I've personally noted that not all linux distributions provide the
> same version of sox;
> some distribute sox with an absolute minimum of sound formats
> built-in. You may have
> to go out and find all the libraries and roll your own sox.
>
> murf
>
>
>
>
>
> On Wed, May 19, 2010 at 10:34 PM, Pham Quy <quyps at vega.com.vn> wrote:
> On Mon, 2010-05-17 at 17:49 +0700, Pham Quy wrote:
> > 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
>
> This question have been asked for a while, I really need some
> help
> here?
>
> Thanks in advance.
> Quyps
>
>
> --
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>
> --
> Steve Murphy
> ParseTree Corp
>
> --
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