Size tradeoffs

[mmodrall]

Hi...

I hope you'll forgive the newbie question but I rip a lot of audio books, trying to get them to fit on one data disk.

I've taken to ripping the cds mono so that I can cut the bit rate while keeping quality.

Recently, I bought a couple of audio book downloads from Audible and Barnes and Noble. Looking at the info in iTunes, it seems that both Audible and B&N achieve their compression not by cutting bit rate and cutting sampling speed.

I was just wondering which tradeoff produces better quality?

To put some numbers to it, I take the cds, take the aiff tracks (which I believe have 44Khz sampling) and rip them to mp3 using 80 or 64kbps mono.

B&N and Audible download audio books have 32 or 64 kbps, *stereo*, 22Khz sampling. The Audible 64kbps stereo audio books are billed as their "cd-comparable" audio books.

So the question is which delivers the best quality vs compression ratio - cutting sampling rate or going mono?

I thought with audio books that going mono was the easiest, least impact tradeoff but 2 commercial services seem to have decided sampling rate was the better trade...

Thanks
Mark

[Sonic Purity]

Recently, I bought a couple of audio book downloads from Audible and Barnes and Noble. Looking at the info in iTunes, it seems that both Audible and B&N achieve their compression not by cutting bit rate and cutting sampling speed.

I was just wondering which tradeoff produces better quality?

To put some numbers to it, I take the cds, take the aiff tracks (which I believe have 44Khz sampling) and rip them to mp3 using 80 or 64kbps mono.

B&N and Audible download audio books have 32 or 64 kbps, *stereo*, 22Khz sampling. The Audible 64kbps stereo audio books are billed as their "cd-comparable" audio books.

So the question is which delivers the best quality vs compression ratio - cutting sampling rate or going mono?

I thought with audio books that going mono was the easiest, least impact tradeoff but 2 commercial services seem to have decided sampling rate was the better trade...

Hi Mark (and All),

I don't deal with audiobooks, yet i'll make educated guesses based on voicework. There may be no particularly good reason that the commercial services are using stereo, or there may be... is there any stereo separation on their files? Maybe some of their products are truly stereophonic, and it is too much trouble to keep track of which. I always, always use monophonic files for single voices needing no sense of stereo separation, no matter what else, to dramatically cut the file size (in half for uncompressed formats).

Again, not being an audiobooks person, i can only guess: if the audio is pure voice and nothing else, 44.1kHz sampling is overkill (unless one wants every last bit of high frequency detail and the quality of the source justifies it). What i do, at least for personal use:

• * Mono
  * 22 kHz or sometimes lower sampling rate, depending upon the quality of the source
  * Experiment with sequentially lower bitrates until i hear degradation, then go back up one step

Since i'm not putting the material on CD and have no concerns about compatibility with MP3 CD players, i tend to use MPEG-4/AAC (i may not have that terminology correct... what Apple likes for iTunes) as i find that compresses a bit better, for smaller files at the same perceived quality (to my ears at least).