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I'm using CDex for converting wav to mp3, and want to ask you guys what version to use;

  • MPEG I has max of 320kbps
  • MPEG II has max of 160kbps
  • MPEG II.5 has max of 160kbps

I'm looking for a better quality, and I want to know if it's better to use a greater version which has a lower kbps (like MPEG II.5)...

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Quality also depends a lot on what encoder you use. – user12889 Apr 19 '10 at 0:33
Do you really need mp3? If your purpose supports other encodings, I'd have a look at benchmarks first as there are more modern codecs out there with better quality per size ratios. – user12889 Apr 19 '10 at 0:35
@user12889: can you post a few links, i've search on google for benchmarks, but no luck, thanks – Remus Rigo Apr 19 '10 at 8:10
up vote 7 down vote accepted

When doing MP3 encoding, MPEG I, II and II.5 have the following meanings:

  • MPEG I refers to MPEG-1 Audio Layer 3 as defined by ISO/IEC 11172-3 (MPEG-1 Layer 3) which offers bit rates ranging from 32 kbps to 320 kbps and sample frequencies from 32 to 48 khz
  • MPEG II refers to a set of extensions to ISO/IEC 11172-3 defined in ISO/IEC 13818-3 (MPEG-2 Layer 3). These extensions provided additional bit rates and sample frequencies including bit rates as low as 8kbps and sample frequencies as low as 16 khz. These extensions are completely backward comparable with MPEG-1 but are geared toward low-bit rate audio.
  • MPEG II.5 refers to an additional set of extensions to add additional sample frequencies, however these are unofficial extensions and not defined by the ISO/IEC. MPEG-2.5 offers sample frequencies down to 11 khz.

Unless you have a specific need for low bitrates or sample frequencies I would stick with the MPEG-1 offerings, they were designed for more general use. Here is an old blog post which discusses some optimal CDex settings

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