analyze a .wav or .mp3 file

analyze a .wav or .mp3 file

[Terry Klarich]

Hello All:

I would like to see if anyone has an idea how to analyze a wav or mp3 file in a shell script to see if there is any audio present;
or, it is a blank file.

The story:
I have used a script for several years called xmonline to listen to xmradio over the internet.  Actually, I mostly used it to
record shows I wanted to listen to later.  Since, the original script used mplayer to play the stream, I modified the script to
write to a file on disk.  It worked well and I could listen to those shows on xm I had to miss for one reason or another.  (my own
xm audio recorder.

Recently, XM has changed their interface such that the xmonline script will no longer work.  I originally thought I cold use
firefox, and the analysis of the network trafic to write a new script.  Using curl as the xmonline script did, I am able to get
logged into the site.  But, when I dig out the stream and try and play it with mplayer, it doesn't work.  I know I'm missing some
simple little cookie or authorization parameter.  (Who knows)

Basically, I have given up on the streaming approach for now.  And, will use the brute force method.  I have my xmradio hooked up
via a sound card.  I am able to listen to xm on my computer with aplay just fine.  I even have a lirc config file that will turn
and off the unit and change channels.  Works great.

My problem is I have no way of knowing if the unit is on or off.  There is only a power toggle ir code.  If there was a power-on,
my problems would be over.

To get around this problem, I will first record a 10 second clip and see if there is anything there or not.  If there isn't, I know
the unit is off.

So, does anyone know a way to discover if there is any audio in a wav or mp3 file using a shell script running in the background?

Any suggestions wellcome.

THANKS!
Terry

P.S.
If anyone wants my failed xmrip script, they are welcome to see what they can do with it.

Re: analyze a .wav or .mp3 file

[Hart Larry]

Well, Terry, an obvious question, what happens if you type file before its 
name?  also, if you do an
ls -l  before its name, it will give you size
Hope that helps
Hart

Re: analyze a .wav or .mp3 file

[Chris Brannon]

Terry Klarich wrote:
> I would like to see if anyone has an idea how to analyze a wav or mp3 file in
>  a shell script to see if there is any audio present;
> or, it is a blank file.

The command-line syntax of sox changed.
As of version 14.3.0, it is sox whatever.wav -n stat, instead of -e stat.

Here's some sample output generated by an audio file of mine.
Note that the data is written to stderr.
Samples read:         215560756
Length (seconds):   9775.998005
Scaled by:         2147483647.0
Maximum amplitude:     1.000000
Minimum amplitude:    -1.000000
Midline amplitude:    -0.000000
Mean    norm:          0.073211
Mean    amplitude:    -0.000002
RMS     amplitude:     0.119737
Maximum delta:         1.026207
Minimum delta:         0.000000
Mean    delta:         0.019383
RMS     delta:         0.035299
Rough   frequency:         1034
Volume adjustment:        1.000

The volume adjustment number always seemed helpful when looking for a blank
file.  It is much greater than 1.00 if the file contains silence.
The other statistics are probably useful as well, but I don't know very
much about digital audio.

-- Chris
PS. I think that you and I have a few common acquaintances outside of the net.
I caught mention of your name several times when I was pursuing an undergrad
CS degree.

73 DE KB5KZZ

Re: analyze a .wav or .mp3 file

[Tim Chase]

Chris Brannon wrote:
> As of version 14.3.0, it is sox whatever.wav -n stat, instead of -e stat.
[snip]
> The volume adjustment number always seemed helpful when looking for a blank
> file.  It is much greater than 1.00 if the file contains silence.
> The other statistics are probably useful as well, but I don't know very
> much about digital audio.

I was about to fire off a similar email, but Chris beat me to the 
punch.  If you just want the volume adjustment, you can add "-v" 
at the end of the command:

   sox my_file.wav -n stat -v

and all it reports is the volume number with no extra 
information.  Can be useful for scripting purposes too.

-tim

Re: analyze a .wav or .mp3 file

[Geoff Shang]

On Mon, 11 Jan 2010, Tim Chase wrote:

> I was about to fire off a similar email, but Chris beat me to the punch.  If 
> you just want the volume adjustment, you can add "-v" at the end of the 
> command:
>
>  sox my_file.wav -n stat -v
>
> and all it reports is the volume number with no extra information.  Can be 
> useful for scripting purposes too.

My suggestion also.

One thing to keep in mind - at least the versions I've used send this 
number to stderr instead of stdout.  No idea why, but if you want to use 
it in a script, you need to keep this in mind, assuming it hasn't changed.

Geoff.

Re: analyze a .wav or .mp3 file

[Martin McCormick]

Terry Klarich writes:
> I would like to see if anyone has an idea how to analyze a wav or mp3 
> file in a shell script to see if there is any audio present;
> or, it is a blank file.

My thanks to someone a couple of yers ago who suggested this
when I asked a similar question. It is slightly inaccurate as to
the time of mp3 files but it failry close.

#! /bin/sh
sox $1 -e   stat 


	I believe it will handle several formats of files.

Martin McCormick WB5AGZ  Stillwater, OK 
Systems Engineer
OSU Information Technology Department Telecommunications Services Group

Re: analyze a .wav or .mp3 file

[Terry Klarich]

Hey All:

Thanks to all for all the good responses.  I found them both very helpful and informative.

I will be using:

sox testfile.wav -n stat -v

It is very simple and reliable.  An empty file has a value of 180.00... 183.00.  Files containing valid audio have anything from
1.00 to about 15.00  (it seams).

I'll continue to work on streaming xm though.  


Hey All:

Thanks to all for all the good responses.  I found them both very helpful and informative.

I will be using:

sox testfile.wav -n stat -v

It is very simple and reliable.  An empty file has a value of 180.00... 183.00.  Files containing valid audio have anything from
1.00 to about 15.00  (it seams).

I'll continue to work on streaming xm though.  


Terry

Re: analyze a .wav or .mp3 file

[Martin McCormick]

I just tried it and it will tell you if a .wav file is silent
but it didn't work on a mp3 so I was a bit mistaken. I think the
sox man page says it can handle mp3's if you have certain
libraries. It definitely worked on a 10-second sample of
stereophonic silence. Actually, it just has 0's for the
maximum, minimum and average levels so you might pipe that
through another decision to get a silence detector.

	Mplayer will convert mp3's to wav files.

Martin

Re: analyze a .wav or .mp3 file

[Martin McCormick]

Thanks for the syntax reminder. I wrote that shell script before
the change. I also need to change another shell script that used
the stretch  command. sox reminds me every time that I need to
fix that. One of these days, a new version of sox will not work
at all.

Martin