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What is -> Audio format - CCITT A-law ... ?
Old 23rd November 2009
  #1
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Big_Bang's Avatar
 

What is -> Audio format - CCITT A-law ... ?

Hey slutzies,

I've been asked to encode some VO to the following, to be used in a phone service.

I have never come across this format, how do I go abouts encoding this? While we are at it, anyone care to give advice on standard stereo buss processing to achieve best quality?

Thanks!!


Bit Rate - 64 Kbps
Audio Sample size - 8 bit
Channels - 1 (mono)
Audio sample rate - 8 Khz
Audio format - CCITT A-law
Old 23rd November 2009
  #2
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Big_Bang's Avatar
 

Well, I just found it in Audition, save as -> A/mu-Law Wave, with 2 options,

A-Law 8-bit
mu-Law 8-bit

I manage to convert the file to the specified characteristics, pretty decent results actually, the problem is saving as A-Law 8-bit... the volume is very very VERY, barely draws a waveform. Barely hitting -52 !!
Old 23rd November 2009
  #3
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nucelar's Avatar
 

Hi,
your client seems not to specify anything about levels. In that case make sure your original waveform peaks at 0 dBFS, preferably use a limiter to get more loudness (like if you master an Audio CD). I would also limit the bandwith to something appropiate for phone playback. At 8kHz sampling rate, cut everything off from 4 kHz up. Then make the conversion to Alaw 8 bit.
16 bit to 8 bit will truncate the least significant 8 bits, so anything wit low level will dissappear.
I use Barbabatch for that purpose, it adds dither and helps a lot with the quantization noise.
Hope that helps
Old 24th November 2009
  #4
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Yes, I am well aware of that, but that is the thing!

I have a healthy 44.1/24 stereo wave that I succesfully convert down to 8bit, but when I go click "save as" to a-law - THEN the wave goes down to -51.

I am at my wits end here... because I can import that, normalize it and save it (just for testing) and the same thing happens. Does not apply to other formats
Old 24th November 2009
  #5
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danijel's Avatar
Quote:
Originally Posted by Big_Bang View Post
Yes, I am well aware of that, but that is the thing!

I have a healthy 44.1/24 stereo wave that I succesfully convert down to 8bit, but when I go click "save as" to a-law - THEN the wave goes down to -51.

I am at my wits end here... because I can import that, normalize it and save it (just for testing) and the same thing happens. Does not apply to other formats
Is there a little-endian / big-endian switch?
Old 25th November 2009
  #6
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Big_Bang's Avatar
 

danijel,

little/big endian... that's byte allocation sequence of some sort, right?

To start, I wouldn't have a clue how to use that, as I had to look this one up, and to finish off... no, I explored every option in Audition and didn't come across that. I would love for you to expand a little on this...!

Would that be, possible, hidden somewhere in prefs?

thanks!!
Old 25th November 2009
  #7
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Regarding the prefs - I don't know. I never used Audition, so that was just a shot in the dark.
What led me to suspect the endianness was your -51dB figure which is close to what you would get if you'd take the 8 most significant bits in a 16bit file and make them the 8 least significant bytes.... But as your target file is 8-bit, there's no endianness to it. That would have to be an internal bug in Audition.
You better try another app. I'm sure there's something free and open source that will do it, like Audacity.
Old 25th November 2009
  #8
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I'd say your a-law codec is busted....my old SoundApp doesn't behave this way.
What with telephones being mono, start there. An aggressive telco ranged bandpass filter prior to any conversion is key, and keeping the needle up on your VU meter (born of telco) will keep the codec from doing too much of it's dirty business - u and A are both companding algorithms designed to reduce dynamic range, so no need to go too crazy with the compression or limiting. You'll yearn for the hi-rez glory of a 64kbps stereo .mp3 after your session...
Old 2nd October 2013
  #9
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Intalik's Avatar
 

Did you figure this out? I have written to AudioEase to ask how to convert to this format too. I don't see an option in BarbaBatch to mix A-law with 64kbps and have it be a .wav format.

I have kind of a rush job here that needs to be done.


Bit Rate - 64 Kbps
Audio Sample size - 8 bit
Channels - 1 (mono)
Audio sample rate - 8 Khz
Audio format - CCITT A-law
Old 2nd October 2013
  #10
I use Sony Sound Forge for all this. The batch process will handle all the conversion and processing, and will append names as well. When you have 2000 files to do, you want to save some time. All conversions have worked flawlessly on phone systems.
Old 2nd October 2013
  #11
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Intalik's Avatar
 

Thanks for answering Bill.

I have used AudioEase's BarbaBatch solely for phone system prompts, but with this requirement from my client of bit rate i wasn't able to use BarbaBatch (unless AudioEase gets back to me with a solution).

Do you have experience with BarbaBatch, bit rate?


OH! and do you know if the MAC version of SoundForge will do the same conversion?
Old 2nd October 2013
  #12
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nucelar's Avatar
 

Quote:
Originally Posted by Intalik View Post
Did you figure this out? I have written to AudioEase to ask how to convert to this format too. I don't see an option in BarbaBatch to mix A-law with 64kbps and have it be a .wav format.

I have kind of a rush job here that needs to be done.


Bit Rate - 64 Kbps
Audio Sample size - 8 bit
Channels - 1 (mono)
Audio sample rate - 8 Khz
Audio format - CCITT A-law
First of all, PCM formats like wav, are not usually described with bit rate. They have a fixed bitrate, depending on the sample rate and sample depth.
In your case, [email protected] makes up a bitrate of exactly 64 kbps. So it's kind of an extra information, but not necessary.
Old 2nd October 2013
  #13
Gear Head
 
Intalik's Avatar
 

Quote:
Originally Posted by nucelar View Post
First of all, PCM formats like wav, are not usually described with bit rate. They have a fixed bitrate, depending on the sample rate and sample depth.
In your case, [email protected] makes up a bitrate of exactly 64 kbps. So it's kind of an extra information, but not necessary.
Thank you very much for that info. I didn't know that was how kbps was calculated. I suspected the 64kbps was unnecessary info for me, but it threw me off.

I've now sent off a test prompt using barbabatch for testing and i'll see if the client can use it.

thanks again!
Old 2nd October 2013
  #14
Years ago, guys with pocket protectors drew up the specs for the phone system providers and handed them out to all of us that don't use pocket protectors... hence the redundant kbps spec.
You might look at Twistedwave, it might be able to export mulaw waves, I know it does do some batch processing, and it's only for MAC.
Old 2nd October 2013
  #15
Gear Maniac
I've used to use Media Cleaner to do batch conversions for phone systems as well. Not sure if they do a demo version.
Old 2nd October 2013
  #16
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Kuba_Pietrzak's Avatar
 

I know, that this sounds weird but:

in Windows XP there was a little built in a system app called SoundRecord (or something similar, I had Polish version of the system)

You can open 48/16 wav and convert it into CCITT Alaw 8kHz...

I did many files with it for automatic tel system some years ago... As simple, as it could be...

And yes, Audacity do the job without any problems too.

best,
Kuba
Old 3rd October 2013
  #17
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Mundox's Avatar
There doesn't exist a phone system that Barbabatch files won't work in.
Old 6th October 2013
  #18
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Smallbudgetguru's Avatar
What is -> Audio format - CCITT A-law ... ?

Try using a software called Switch. It may have what you need.
Old 19th October 2013
  #19
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Intalik's Avatar
 

Word came back. File was accepted. Barbabatch did the trick. And just for the record, AudioEase support did get back to me with a clear answer.
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