Problem: I have to encode sounds as efficiently as possible while maintaining best quality. The only way I can do this is by encoding with different bit rates, and then listen to the files.

I'm on the Mac and I listen to two versions using preview and the arrow keys. But it is hard to judge which is better because I can't set a loop region and listen to A / B over and over again starting at the same point every time.

Is there a tool which makes this task of comparing two differently encoded files easy?

9 Answers 9


Sonnox makes a plugin for music mixers to quickly A/B what different MP3/AAC bit rates will sound like. It might be the solution that you are looking for.



I go about it in a slightly different way, I like to listen to artefacts on their own. What I do is encode the samples and then decode them back to wav. Then I import them into a DAW invert the phase on the decoded files and then subtract the original uncompressed file so you are left with the artefacts. I will then choose the compression based on the annoyance factor for the artefacts.


that's a great question. In theater have A\B switches like this to test microphones against eachother. In terms of a software solution, if I weren't writing my own tool in MAX\MSP, I'd be inclined to use qlab (www.figure53.com) to play the two files in sync with eachother. Then trigger "fade" cues with hot keys to toggle which is audible as they both play continuously


If you're looking to do it on the cheap, and you don't need sample-accurate playback, you could always use Quicktime Pro.

Enable the preference 'Play sound in frontmost player only', hit 'command-return' to play all open files, then use the keyboard to toggle between the open windows.

Quicktime Pro is able to loop a selected area within a file.


I think ABX will work with multiple types. It's an A-B testing app for listening tests. 10 blind listens and an average score.



Wiretap Studio lets you loop sections of audio, and change the compression format/settings during playback. It's also a really useful tool for capturing any audio source on your Mac.



I would probably approach this by loading up Cockos REAPER and then "solo-ing" the particular track that I want to audition. I am fairly sure REAPER will support looping and all the required functionality.



For a conversion program, check out Amadeus Pro at www.hairersoft.com. It's an awesome editor, batch processor and converter that I use almost every day.

If you have access to a multitrack editor, try this trick for conversion. Make sure that you have a full-quality .WAV copy of the file you are interested in comparing. On one track, put the original wave file. On each subsequent track, place each version of the converted files. In order to compare, all you need to do is play the original on top of one of the converted files with the polarity of one of the two tracks flipped.

What this does is take two supposedly-identical files and play them in opposite polarity. Of course, the converted file has some data missing, so any material present in the original wave that the conversion deleted will play through. In essence, you're hearing a sonic representation of all the material that the conversion process deleted. With this setup, you just need to do a comparison of each conversion type to the original then pick whichever one has the least "missing" audio playing.



I've found that DJ software works. Just load up both tracks, make sure that the output is set to the higher of the tracks, and you can use the fader to switch between the tracks. I've had some success using the free app Mixxx.

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