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Topic: 2pass abr vs. vbr for a specific file size? (Read 4393 times) previous topic - next topic
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2pass abr vs. vbr for a specific file size?

If I would like to end up with about the same file size for a LC-AAC rip of a WAV file using neroaacenc.exe, am I "better off" (subjective sound quality) using 2pass abr (-2pass -br xxx000) or vbr (-q 0.yy)? I've read that just going with vbr (-q 0.yy) is best, but if that's so, why would Nero supply the -2pass switch?

I use dbPowerAmp's UI to Nero's aacplusenc.exe because it's pretty simple to deal with, but it doesn't allow for the 2pass switch as far as I can see. I've also used EAC but don't like doing that because I have to change everything when I rip to FLAC or anything else, for that matter. I've fooled around with neroaacenc.exe in a command window, but that seems the most awkward way of all.

I've looked at the 2pass discussions on Hydrogen Audio, but they seem to rapidly go off on a tangent. Maybe there's a post that's really clear, but I've missed it.

Thanks!
Otro mundo es posible.

2pass abr vs. vbr for a specific file size?

Reply #1 –
I don't know why 2 pass is there as a general option. I'd stick to vbr unless i need very specific bitrates. I did test aac a year or so ago on very hard artificial stuff and abr was really no star performer - a bit worse than vbr on a few samples and better on one. In the end I couldn't find a concrete case for ABR with aac but I wouldn't say its worse than vbr either at higher bitrates.

2pass abr vs. vbr for a specific file size?

Reply #2 –
Since vbr can't guarantee a bitrate, and thus, your question implies fiddling with the -q parameter until you get your desired size, I would think that abr is a lot better for that.

2pass abr implies that instead of distributing the bitrate evenly over the ABR window, there is a first pass that tries to guess the difficulty of the different parts, and prepares the codec to spend the most bits on those parts, given the bitrate constraint.

for completeness: 2pass vbr is not an option (i.e. the option is not applicable to vbr).

About the quality of ABR -2pass vs VBR, i have no information, but it should be better than "plain" ABR