exporting wav to ulaw

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Audacity 1.3.x is now obsolete. Please use the current Audacity 2.1.x version.

The final version of Audacity for Windows 98/ME is the legacy 2.0.0 version.
jlr
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exporting wav to ulaw

Post by jlr » Wed Jul 21, 2010 3:49 pm

I have a telephony application running on Windows platform. Requirements for wav files are CCITT u-law, mono 8bit, 8khz. I take a standard wav pcm file, modify it and export the file to ulaw; the application will not play the file. If I take the same pcm file and use MS Sound recorder to convert it, the application plays it just fine. When I export I am selecting "other uncompressed files"; then clicking "options" and selecting "WAV (microsoft)" as the header and "u-law" as the encoding. I have tried other combinations but the application will not play the file or it is static only. Any help on this?

Gale Andrews
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Re: exporting wav to ulaw

Post by Gale Andrews » Thu Jul 22, 2010 3:23 am

jlr wrote:I have a telephony application running on Windows platform. Requirements for wav files are CCITT u-law, mono 8bit, 8khz. I take a standard wav pcm file, modify it and export the file to ulaw; the application will not play the file. If I take the same pcm file and use MS Sound recorder to convert it, the application plays it just fine. When I export I am selecting "other uncompressed files"; then clicking "options" and selecting "WAV (microsoft)" as the header and "u-law" as the encoding. I have tried other combinations but the application will not play the file or it is static only.
I am repeating the reply I have already given you by e-mail. I am also moving this to the correct Windows Beta Forum.

Please note that 1.3.7 Beta is obsolete and the current Beta is 1.3.12:
http://audacityteam.org/download/beta_windows

You can keep up-to-date with news of Audacity releases by subscribing to the announcements mailing list at the bottom of our home page:
http://audacityteam.org/#announce

As regards your issue, have you changed the project rate bottom left of the Audacity screen to 8000 Hz? This determines the sample rate of the exported file.

Sound Recorder on Windows XP recognises the file exported from 1.3.12 as CCITT u-Law, and dBPowerAmp and other analysis tools also report that file as having CCITT encoding.

To investigate further we would need to know exactly what version of Windows you are on, have a copy of the file you exported from Audacity that isn't recognised by the application, and a link to (or copy of) the telephony application.




Gale
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jlr
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Re: exporting wav to ulaw

Post by jlr » Thu Jul 22, 2010 12:56 pm

I did verify that the file is set to 8khz (in lower left corner). I too saw that MS Sound recorder indicated the file was in the proper format. I downloaded Audacity 1.3.12 and tried that with the same results. I cannot give you access to the system or application for proprietary reasons and customer security (I understand this ties your hands) but the system is a Vertical Networks Instant Office running on MS NT 4.0. Vertical Wave IP runs on 2003 Server and has the same requirements. I have not had a chance to try it on that system but suspect I would have the same results. I realize Audacity is done by volunteers and is freeware so I don't expect you to put much effort into addressing this but I belive there is a problem withh your CCITT encoding. I have seen comments on other forums referencing Audacity CCITT problem with Cisco switches also. I have attached the file.
Attachments
8081 ccitt aud.wav
wav pcm exported to ulaw
(55.24 KiB) Downloaded 631 times

Gale Andrews
Quality Assurance
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Joined: Fri Jul 27, 2007 12:02 am
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Re: exporting wav to ulaw

Post by Gale Andrews » Fri Jul 23, 2010 5:46 am

jlr wrote:I did verify that the file is set to 8khz (in lower left corner). I too saw that MS Sound recorder indicated the file was in the proper format. I downloaded Audacity 1.3.12 and tried that with the same results. I cannot give you access to the system or application for proprietary reasons and customer security (I understand this ties your hands) but the system is a Vertical Networks Instant Office running on MS NT 4.0. Vertical Wave IP runs on 2003 Server and has the same requirements. I have not had a chance to try it on that system but suspect I would have the same results.
Thanks for the Audacity file. I don't have access to NT4.0. Can you provide an example file produced by MS Sound Recorder that your application plays?
jlr wrote:I have seen comments on other forums referencing Audacity CCITT problem with Cisco switches also.

Could you post a link to those threads possibly. It might give us some more information on the differences we are looking for.



Gale
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jlr
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Re: exporting wav to ulaw

Post by jlr » Fri Jul 23, 2010 2:05 pm

file attached that was converted to ccitt by MS Sound Recorder.
Attachments
8081 ccitt ms.wav
(55.29 KiB) Downloaded 592 times


Gale Andrews
Quality Assurance
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Joined: Fri Jul 27, 2007 12:02 am
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Re: exporting wav to ulaw

Post by Gale Andrews » Sat Jul 24, 2010 6:09 am

Thanks for the attachment and topic links. I wouldn't expect u-Law with AU extension to work as someone in one of those topcis was trying. Does the attached u-Law file produced by Audacity 1.2.6 have the same problem?



Gale
Attachments
CCITT_U-LAW_126 .wav
U-law with WAV header produced by 1.2.6
(430.72 KiB) Downloaded 493 times
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jlr
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Re: exporting wav to ulaw

Post by jlr » Fri Jul 30, 2010 5:43 pm

Sorry for delay; any file exported as ulaw in Audacity will not work; the only one that has worked is the one done by MS SR.

Gale Andrews
Quality Assurance
Posts: 41761
Joined: Fri Jul 27, 2007 12:02 am
Operating System: Windows 10

Re: exporting wav to ulaw

Post by Gale Andrews » Sat Jul 31, 2010 3:49 am

Can you see if the attached plays in your app? It's a file produced by Audacity, but everything before the data chunk has been replaced with that from the file produced by MS Sound Recorder.

At the moment I'm wondering if libsndfile which Audacity uses to export WAV really produces compliant G.711 u-Law. Although the source code seems to imply it does (with the comment that G.711 is "very difficult to follow"), their web site only refers to u-Law as "u-Law". The Fact chunk is definitely at a different offset in the Audacity file.



Gale
Attachments
8081_ccitt_audacity_not_read_by_3rd_app_mod1.wav
(55.24 KiB) Downloaded 573 times
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jlr
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Re: exporting wav to ulaw

Post by jlr » Mon Aug 09, 2010 3:52 pm

yes, this new file does play in my app.

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