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mp3packer can't make 112kbps CBR frames
timcupery
post Feb 21 2013, 18:15
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I don't know the best way to quickly describe this in a subject line, but mp3packer appears to only recognize 96kbps and 128kbps as valid "CBR destinations."

If I take a CBR file and process it to VBR with mp3packer, and then process the resulting VBR file back to CBR, it will typically end up at the same bitrate as the initial CBR file.
For example, a 192kbps CBR file may condense down to an average VBR bitrate of 187kbps. And when I process that 187kbps file back to CBR, it ends up as a 192kbps file again. This pattern holds with initially-CBR files at all bitrates except for 112kbps.

If I take a 112kbps CBR file and process it to VBR through mp3packer, and then run the resulting VBR file back to CBR, it ends up as 128kbps CBR. This is a consistent pattern across computers (all Windows) and all originally-112kbps CBR files.

Does anyone know why it happens this way? Is there something atypical about a 112kbps frame that isn't true of other mp3 frames? Or is it simply a programming overlook in mp3packer? (or some other explanation)


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God kills a kitten every time you encode with CBR 320
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timcupery
post Feb 21 2013, 23:42
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Group: Members
Posts: 780
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perhaps a simpler way to explain this:

QUOTE (timcupery @ Feb 21 2013, 14:21) *
When converting an mp3 file with max frame size of 112kbps, to CBR, mp3packer will nevertheless convert the file to 128kbps instead of 112kbps. It even works with files that start out as 112kbps CBR: if I process them to VBR, and then back to CBR, the resulting CBR file is 128kbps. It seems that 112kbps is "skipped over" amongst CBR options; I haven't noticed this happening for any other mp3 bitrate.

This happens with older versions of mp3packer, and also with 2.04.


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