[App_rpt-users] uLaw playback

[Dwaine Garden VE3GIF]

I use the AT&T site and just type what I want the message to be.  Pick the voice and listen before I spit out the ulaw audio file.  Had my whole IVR system menu done that way.  It was mint.

Jon Rorke <jrorke at cogeco.ca> wrote:

>When I make my audio files in Audacity, I export to a wav file then I 
>export to ulaw.
>I then play the wav files back to verify they sound ok.
>
>Works great.
>
>Jon VA3RQ
>
>On 8/6/2013 4:41 AM, Ken wrote:
>> If the original wav file is not limited to -6 dBfs (minus 6 dB relative to
>> full scale) you can reduce the level "on the fly" by using the lower case
>> "v" for volume control.
>>
>> For example, this reduces the volume to half what it was (-0.5)
>>
>> sox -v -0.5 -t raw -U -c 1 -r 8000  (etc...)
>>
>> 73
>> Ken
>>
>>
>>> -----Original Message-----
>>> From: Angelo Glorioso [mailto:n5uxt at hotmail.com]
>>> Sent: Monday, August 05, 2013 10:39 PM
>>> To: Ken
>>> Subject: Re: uLaw playback
>>>
>>> Hi Ken,
>>>
>>> Thanks for your reply. I was able to find the syntax for sox. It worked
>> great. It
>>> took my wav file and converted it over to ulaw. I used :
>>>
>>> sox -V n5uxt.wav -r 8000 -c 1 -t ul -w n5uxt.ulaw
>>>
>>> It was simple and fast.
>>>
>>> 73, Angelo
>>>
>>>
>>> ----- Original Message -----
>>> From: "Ken" <ke2n at cs.com>
>>> To: <app_rpt-users at ohnosec.org>
>>> Cc: "'Angelo Glorioso'" <n5uxt at hotmail.com>
>>> Sent: Monday, August 05, 2013 7:54 PM
>>> Subject: uLaw playback
>>>
>>>
>>>> I have read where uLaw produces 14 bit audio (-8159 to +8158
>>>> numerically-speaking)  - see Wikipedia on this, for example.
>>>>
>>>> I am guessing this is the range of numbers used by app_rpt.
>>>>
>>>> Your 16-bit WAV format is going to produce +/- 32768 (numerically-
>>> speaking
>>>> again).
>>>>
>>>> So - you need to divide the WAV output by a factor of 4 to get into the
>>>> range that uLaw supports.
>>>>
>>>> The tutorial on using Audacity for app_rpt:
>>>> http://images.ohnosec.org/app-rpt-audacity.pdf  says to normalize at
>> -6dB.
>>>> You really need to follow that advice to get clean audio.
>>>>
>>>> "Normalize" will set the loudest sound to the amplitude you select.  If
>>>> there are a lot of sound "spikes" in the audio track, you can end up
>> with
>>>> a
>>>> pretty low average sound level.  I have found the best way to fix this
>> is
>>>> some judicious use of the Audacity "hard limiter" function. It really
>> does
>>>> not damage the sound quality, when used within reason.
>>>>
>>>> 73
>>>>
>>>> Ken
>>>>
>>>>
>>
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>
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