Comments on: The Secret Lives of MP3 Files

By: PCPete

PCPete — Fri, 25 Jun 2010 04:13:40 +0000

Guys, the Hz figure is the sampling interval for the original audio before compression. If you have a low bitrate compressed file that you “up convert” using a higher sample rate, then that’s why the filesize doesn’t change – it’s resampling the same signal, just faster!
To see the effect in action, try DOWN converting a PCM/WAV file at 44.1kHz (or higher if your compressor allows it), and you’ll see a significant reduction in the filesize as the sample rate is dropped. It won’t be as “large” as the effect of the bitrate selected, but it will vary.
HTH.

By: Doug Kaye

Doug Kaye — Tue, 10 Mar 2009 19:44:46 +0000

Zen, You’re always better of starting with the uncompressed original. If you decode an MP3 then re-encode, you’ll lose some quality. As you discovered, the sample rate has no effect on the MP3 filesize. Only the bitrate matters in this regard. You’ll find that sample rates that are multiples of 11025 play on more players. 22050 and 44100 are almost universal. Some devices (and Flash players) won’t play 24000, 32000, 48000, etc.

By: Zen Kai

Zen Kai — Tue, 10 Mar 2009 19:39:03 +0000

Doug,

Thanks so much for this! I’ve been looking for some relevant information on encoding for some time now, and this totally fits the bill!

I’m really into audiobooks, and have the equivalent to a season pass to Audible. Unfortunately, my car’s MP3/CD player is finicky as hell, and complains about 90% of what’s fed into it.

I’ve found that converting from AA to MP3 and breaking the 150+MB file into many smaller files will allow it to play acceptably, but I had no clue what to set Goldwave’s conversion settings to.

Kbps is old hat, I understood that before, but the Hz options (8000, 11025, 12000, 16000, 22050, 24000, 32000, 44100, and 48000) have always been a mystery to me. They don’t seem to yield much different file sizes; the Kbps seems to be the only significant factor there (I notice a difference of a few kb. Oddly, 16000 yields a slightly LARGER file than 22050).

This is spoken word, sampled from a 64kbps, clean original. On a related note, with reference to your data about artifacts, am I better off starting with a CD-quality file and converting down, or starting with the desired format and simply breaking it up?

By: Geek News Central

Geek News Central — Fri, 15 Dec 2006 09:50:13 +0000

GNC-2006-12-15 #225

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