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-b128 in alt-preset standard
olcios
post Dec 31 2001, 15:32
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Hi ppl, plz explain me: is it really so important to use -b128 in "alt-preset standard"? as far as i remember --dm-presets were using -b112 and they were rated very high in the AQ1 test few months ago. I don't know of any reports of very audible artifacts caused by -b112 in compare to -b128. And even if there are some, I think it's not the point to raise the minimal bitrate but to improve the VBR engine so that it would choose 128 instead of 112 for those samples.

I think it's reasonable, because there certainly are some short parts of music which sound perfect at 112. I know this is theory only, but I think that, generally speaking, improving quality by raising the minimal bitrate is missing the point of VBR.

Thx, and Happy 2002.

Olcios
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amp
post Dec 31 2001, 18:31
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Hi

I think that the -b 128 switch it's only for 'security reasons'. You won't obtain lower bitrates, using for example -b 32, because the preset uses a high -V value, I think it's -V 2. If you want to obtain a lower bitrate, try -V 4 for example.

Greetings
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Dibrom
post Dec 31 2001, 22:03
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-b128 doesn't raise bitrates except on mono recordings which would fall below 128kbps. For those mostly rare cases (considering the majority of what people will be encoding) -b32 could be used. Also, according to some tests (don't have the link handy at the moment, I think it's 2BDecided's page), some older MP3 decoders have much more success with VBR files if the lowest bitrate used is 128kbps. These decoders are obviously not compliant to the specification but it's another small reason to default 128. I may change my mind about all of this in the future if I see another convincing argument the other way though.

In addition, Wombat has found at least 1 sample (which I haven't listened to yet since I just moved and my equipment isn't setup) where -b128 did offer a slight improvement in quality.
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olcios
post Jan 2 2002, 16:33
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ok, thx. I'm waiting to see if it is necessary to use -b128.
The difference is very slight indeed, ~0.05% (that is 0.0005), usally a few kBytes. That is a few hundreds of kBytes less on a CD. In most situations, that's too small to notice, indeed.

Olcios
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Wombat
post Jan 2 2002, 20:03
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Hello,

I found this file which preset standard has problems with only -b 112.
With -b 128 it is much better but still not perfect. It is a shortened version of the one i sent Dibrom.

I try to offer it here:

www.halke.net/files/Sophia2.zip

You can hear added noise from sec 1.2-2 and 4-6.

btw. preset extreme has no problem at all with this.


Wombat
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