Splasm Software Discussions

I use ABB a lot to join audiobook tracks downloaded from a couple of online vendors. On one, the typical audiobook is 48kbps, mono, with a sample rate of 24 kHz. (Some, where stereo would make a difference, are usually 96kbps, stereo, sample rate 32 kHz.) On the other, it's typically 64kbps, stereo, 44.1 kHz. My goal in ABB would be to get a file that's as close in quality to the original MP3 as possible.

I've found, through experimentation, that a happy medium within ABB is 48kbps, mono, 32 kHz. My question is this: if I have a 64kbps file and import it at 48kbps, am I going to get roughly 48kbps quality, or something less (for example, 64x0.48)? If the original sample rate was 44.1 and I use 32, am I going to get "32" quality, or am I further degrading an already sparse file? What if it's the reverse -- originally sampled at 24, say, and I use a sample rate of 32 to import it? What's the likely effect?

I'll make this more specific. I used ABB to join a 200-track audiobook that was 64/stereo/44.1. When I imported it with the same settings in ABB, it sounded scratchy. When I re-imported it as 48/mono/32, it actually sounded better. It may be in this case that switching from stereo to mono was more important than any of the other factors. But I'm still curious.

If it's possible to describe the function of bit rate and sample rate in a way that makes sense to someone who barely made it through high school physics ... I would be grateful. Which plays the biggest role in determining quality of the sound reproduction? How do they work together? If I'm importing a file that's already been compressed for online distribution, should I always try to match the original bit rate and sample rate in ABB?

Still wondering about this. Some of the recent changes have rendered the question about imports moot. But I'm still uncertain about build options. Let me try to rephrase it.

If I'm building an audio book based on an inported mp3 file, should I always try to match the settings of the original file?

I try to find a reasonable balance between recording quality and space consumed. In most cases I find that 48 bps / 32 mhz / mono is adequate for my purposes. But if I've imported an mp3 file that was created at 64 bps / 44.1 mhz, what's the likely effect on sound quality? I know it won't be as good as 64x44.1, but will it be as good as if the original file was 48x32? Or will it be something more like a 48 bps sample of an already-sampled file?

Plus here's a suggestion: if I'm importing mp3 files, is there any way for ABB to detect these settings automatically and make the build correspond to them?

its really up to your ear, and nothing else. Re-encoding any lossy format into the same or another lossy format will always result in some degradation of sound quality. The only real situation where it might not be worth your time is encoding a low quality file into a higher quality one.

So moving from an mp3 with 64kbps/44.1 to the equivalent Audiobook quality is a fine choice, or reducing it a bit if you like the files a bit smaller also works. I would just try a few and settle on your own personal standard.

Since Audiobook Builder can bring in many formats in many different qualities, an auto detect for quality would be messy at best. You can get a quick rundown of file quality by moving through your files in your project with the 'show details' pane open at the bottom to get the information you need. We do allow for pass through if all of the imported files are AAC and are of the same bitrate/frequency. This allows the files to be joined together without re-encoding.

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Randy Knoble
Splasm Software
www.Splasm.com

Thanks! I use "show details" for chapter names but somehow had missed the other info.