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Specific mono conversion (CCITT u-Law 8.000 kHz, 8 Bit, Mono)

Explorer ,
Feb 21, 2017 Feb 21, 2017

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I recorded some "On-Hold" messages for our phone system which I produced the finals in Audition CC.  Unfortunately it ends up that the phone system (Avaya) requires a specific recording type and I'm not figuring out an export scheme to match what it requires.

CCITT u-Law 8.000 kHz, 8 Bit, Mono

Will someone knowledgeable on audio formats and the ability of Audition to export to this format let me know the settings or if it's even possible?


Thanks,
Dave

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correct answers 1 Correct answer

Community Expert , Feb 21, 2017 Feb 21, 2017

In that case, probably these settings:

8-bit wav.JPG

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Community Expert ,
Feb 21, 2017 Feb 21, 2017

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You haven't said what the extension is, but the principle's the same whatever you use. Most probably the correct format container will be in libsndfile, so what you are looking for is something like this:

8-bit.JPG

So you use the pulldown  at the end of the line to select the format, and then click on 'change' to select the type of recording you want (8k 8-bit mono), and in the 'format settings' box use Change to select something appropriate (which is slightly wrong in that picture!), and then put the extension you want on the end of the file name.

If you haven't done this before, then there are a few things you need to be aware of before saving in such a restricted format. I covered most of it in another thread not so long ago, and you can see that here:

Audio Format File Conversion

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Explorer ,
Feb 21, 2017 Feb 21, 2017

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The extension is WAV.  Sorry about that.

I will look at what you've shown.

Thanks for the help.

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Community Expert ,
Feb 21, 2017 Feb 21, 2017

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In that case, probably these settings:

8-bit wav.JPG

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Engaged ,
Jun 24, 2018 Jun 24, 2018

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These settings worked for my Verizon VOIP system, but the quality is horrible with a lot of hiss in the background. The original file was a 44100 Hz 16-bit Mono that was crystal clear. What have I done wrong?

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Community Expert ,
Jun 24, 2018 Jun 24, 2018

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kcrossley  wrote

 

These settings worked for my Verizon VOIP system, but the quality is horrible with a lot of hiss in the background. The original file was a 44100 Hz 16-bit Mono that was crystal clear. What have I done wrong?

Nothing really - it's what you haven't done that makes the difference here. You have to bear in mind that 8-bit audio has a significantly higher noise floor than 16-bit audio - if you want to work out where it is, it's 6.02dB/bit. So that gives you a signal to noise ratio at the very best of about 48dB, and that's worse than an old cassette recorder!

 

So what you have to do is optimise your speech recording to fit in with these essentially restricted parameters. This means that to start with, you need to normalize your signal so that the peaks are almost at 0dB. This optimises the signal as far as the level is concerned, but you are almost bound to have too much dynamic range in it. Everything you need to fix this is in Effects>Amplitude and Compression. So in Normalize, select the 'normalize to -.1dB' preset, and apply that (if that's not on your system it's easy to make). Then open the Hard Limiter, and select the 'Limit to -1dB' preset and apply that. You may also like to experiment with the speech volume leveler, but if you do, then don't go beyond 'medium', and you will probably need to re-normalize afterwards, to get the signal back as close to 0dB as you can.

 

Yes, this makes a horrible mess of your recording, but I'm afraid that's inevitable - it's intended for a restricted bandwidth carrier, and it only has to be intelligible - no niceties like quality come into it, I'm afraid. The Laws of Physics rule those out completely in this scenario.

 

(Please note extra comments below about starting with a 16-bit file fed to the encoder - this should also help.)

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Engaged ,
Jun 24, 2018 Jun 24, 2018

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Thanks Steve. All of my peaks were already under 0dB, so what I ended up doing was taking the compressed 8-bit file and applying the Adaptive Noice Reduction filter, which helped. It still doesn't sound great, but at least the hiss is gone. I may try some other tweaks as well. Thanks again for your help.

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New Here ,
May 31, 2023 May 31, 2023

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I know this is a bit old. But I found that if you make the sample rate 16-bit under sample type, but leave the format settings in u-law 8bit PCM, it will dramatically reduce the noise introduced to the audio file, and the phone system will still recognize it as a 8kHz 8bit file.

Screen Shot 2023-05-30 at 1.48.22 PM.png

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Community Expert ,
May 31, 2023 May 31, 2023

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Yes this is probably correct - it gives the u-law part of the encoder potentially more to work with at the bottom end, which is bound to improve the noise situation a bit.

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New Here ,
Feb 23, 2022 Feb 23, 2022

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Disagree SteveG,

I tried almost every combination of settings within the same parameters given and the onlt thing that worked and produced identically sized file with NO hiss was Audible, so the physics/lossy codec argument holds no water.  This conversion/export format needs examined as it introduces EXTREME hiss into the recording where Audible did not.

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Community Expert ,
Feb 24, 2022 Feb 24, 2022

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I do like it when people try to defy the laws of physics, especially when they've backed their rather specious claims up with ZERO facts! And absolutely no evidence, either. I suggest that a careful reading and understanding of the contents of this document might be a good idea if there's really any doubt as to what is happening.

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New Here ,
Sep 03, 2024 Sep 03, 2024

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I know this thread is over 7 years old at this point so this is a long shot, but @SteveG_AudioMasters_ I've seen your responses in a few different places and your insight and assistance here has been immensely helpful! Unfortunately, it looks like the old hyperlinks to the more in-depth threads you mention are broken (Like this one to the Audio Format File Conversion), possibly because it looks like Adobe overhauled the forum URLs at some point -- and I've been looking for an hour but finding the post in the depths of the forum backlog is proving difficult. I'm extremely interested in reading your guides though! I was wondering if that information is in fact still floating around somewhere, or if you'd be willing to revisit the topic? I don't want to ask too much or make you write entirely new threads though, maybe compiling some new working links to some of the more in-depth write ups you've done over the years in one place? I'm not sure the best solution, I just know the current navigation and search options for the forums are being extremely unwieldy haha.

 

But hey, if you actively post about audio engineering in other spaces or about other software as well, I'd love to know!
Regardless, thank you so much for all your time and effort in these forums - You've clearly been around a while and know what you're doing, and are passionate about helping make the information accessible for people, thank you so much!

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Community Expert ,
Sep 04, 2024 Sep 04, 2024

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Sorry, don't have time to redo any of this, but also, I'm not sure what has happened to the old threads. Yes, Adobe 'rebuilt' the site a few years ago, and this effectively rendered every single previous link useless. There doesn't appear to be any cross-linking of thread numbers and they also ditched the rather useful FAQ section that we used to have. I'm not really sure what the purpose of the rebuild actually was, but it does not appear to serve the end users very well...

 

So it's possible that it's still there, but a search doesn't reveal it to me either, I'm afraid.

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New Here ,
Sep 05, 2024 Sep 05, 2024

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Yeah it's really unfortunate, I wish there was literally any chance of them fixing it. Ah, well. I'll try to sit down and make a separate thread asking about how to save in extremely restricted formats at least, and if you have time to give it a visit I'll see you there! No pressure though, and thanks again so much!

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