-V2 gives way too high bitrate!?! Options

[masterridley]

I use dbpoweramp and I encode flac tracks to LAME 3.98r -V2. Usually this results in ~170 to ~220 kbps files (close to 192kbps CBR quality)

Well, not so for 2 As I Lay Dying albums that I have (think REALLY LOUD metal). When I encode those I get 230-270 kbps and of course the resulting files are quite big.

My question is: is this a bug or completely natural?
Furthermore (if it's not a bug), isn't it just better to encode in 192kbps and get a smaller file, since that's the quality I was going for anyway?

Cheers

[robert]

If global gain is zero, resolution will need to be increased (and quantization lowered) on every other scale factor band.

The sentence from the wiki makes no sense. Though the corresponding section at mp3-tech.org does explain the sfb21 problematic very well.

Scale factor refers to how much quantization (loss of precision) is applied to each band, where higher quantization causes greater compression, and consequently less variation between the minimum and maximum values (resolution).

- scale factors allow to reduce the quantization step size per sfb, within a limited range, as a deviation from the global step size (global gain).
- quantization is a process. larger quantization step sizes allow greater compression, this results in more quantization noise.

Global gain is an extra quantizer that affects all bands simultaneously.

This is plain wrong.

The only way to increase the resolution on sfb21 is therefore to reduce the global gain quantization, since global gain applies to all bands.

Needs correction.

If global gain is zero, resolution will need to be increased (and quantization lowered) on every other scale factor band.

If global gain is zero, then there is nothing you can do anymore.

LAME implements the -Y switch as a way to activate the alternate logic that CBR uses in respect to quantization noise in the sfb21 band.

No, it's an off switch. It turns off code that's used in higher quality VBR settings.

Since the sfb21 does not have quantization, its quantization noise is not evaluated.

Makes no sense. The content of sfb21 will surely get quantized.

In MPEG2 (16,22,24Khz), it is sfb12.

This is wrong. Long blocks have 22 sfbs (sfb0 - sfb21), short blocks have 13 sfbs (sfb0-12). The short block sfb12 has no scale factor of its own, like the long block sfb21.

This post has been edited by robert: Apr 1 2010, 13:44