Slight distortion when converting to mp3?

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Thomas
Posts: 2
Joined: Tue Aug 30, 2011 4:10 pm

Slight distortion when converting to mp3?

Post by Thomas »

Hi there,

Just thought I'd pop in to see if anyone could help. I've searched through all the previous forum posts and tried what I can to fix this problem but can't seem to work it out.

I'm using a iMac running Lion with 4 gig of ram and a 2.66 ghz intel core 2 duo, version 2.0.4 (1356) of Amadeus Pro, and recording straight into my computer using Call Recorder for Skype Calls by Ecamm.

I co-present the UK running podcast Marathon Talk with a friend and using a similar set-up we each record the Skype call as a .mov file after which I split it in two and use each of our audio files recorded straight to the computer i.w. discarding the audio that has been streamed over the internet.

Up until recently everything has been fine but on upgrading to Amadeus 2, Lion, and an SE2200a mic with Saffire 6 pre-amp, I've started to get slight distortion on my friend's side of the audio when converting into mp3. It sounds perfect in Amadeus format and also if I turn it into an mp4 file, but no matter how high I set the quality it distorts in mp3 (which I need to use).

You can find a short audio clip,

in Amadeus format - http://bit.ly/pmitnR

in mp3 - http://bit.ly/qhrNgX

in mp4 - http://bit.ly/o1vib3

in AAIF - http://bit.ly/o79ll5

Interestingly, when I convert to AIFF it only comes through one channel, you can hear my background noise in the other, could this be something to do with the problem? i.e. my friend is only recording one channel which then plays up when converting to mp3? (It looks fine in Amadeus?)

Any help, thoughts, or input massively appreciated.

Many thanks,

Tom

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Martin Hairer
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Slight distortion when converting to mp3?

Post by Martin Hairer »

Hi, I just created the file at

http://dl.dropbox.com/u/2623632/BestTest.mp3

I cannot hear any artefact there, even with good headphones. The settings I used are:

Encoding type: VBR
Encoding quality: 0 (Best)
VBR quality: 2

Regards,

Martin

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Thomas
Posts: 2
Joined: Tue Aug 30, 2011 4:10 pm

Post by Thomas »

Hi Martin,

Thanks for getting back to me so quickly.

It seems that my problem may have been that I was using a constant bit rate? Switching to VBR does seem to stop this happening. Do you have any idea why that might be? I've been using Amadeus for quite a while on a constant bit rate of 64 and not had a problem?

I guess it won't really matter, although the file sizes will I think become somewhat larger?

It's also odd that it only seemed to happen with my co-host's voice and not mine. Is it possible that there is a setting that has changed at his end which is in turn creating the need for a VBR when encoding to mp3?

Apologies for my clear lack of sound editing knowledge!

Thanks for your time,

T

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Martin Hairer
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Slight distortion when converting to mp3?

Post by Martin Hairer »

Do you have any idea why that might be?
I don't know for sure, but I suppose that it's pretty normal to have audible artefacts at 64kbps. It may have to do with the background noise: if there's more of it, some of the bandwidth may be wasted in trying to encode the noise. Regards,

Martin

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HairerSoft
http://www.hairersoft.com/




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