Quant 3 versus 2-pass VBR

[aabxx]

Will constant quant 3 encodings give equal quality to 2-pass VBR with an average of say 3.5?

Anyone have any thoughts on that? The average quant of my 2-pass VBR-encodings are usually around 3.5 to 4. They have the advantage that there will be quant 2 frames, but the constand quant has the advantage that the quants won't fluctuate as much.

I'm wondering whether sacrifising quant 2 frames still can give excellent quality?

[Teegedeck]

Coincidentally I just answered a simliar question in an unrelated thread; so here's some copy & paste (mainly) :):

The occasional quant=2-frame will not improve quality visibly. What improves quality in two-pass is that quantizer doesn't arbitrarily fluctuate between 3 and 4 but that (hopefully) big frames are more like to receive a '4' and the bitrate thus saved goes into some smaller frames that can use '3'; that's what curve-compression should do.

Constant quantizer encodings have a theoretical quality advantage only if quantizer doesn't fluctuate at all; i.e. if only even quantizers are used (like 3.00). But if the predicted filesize for an even quantizer encoding is well below the filesize you wanted to reach, then a two-pass encoding that reaches that filesize will always have an advantage.

On the other hand, too big fluctuation also hurts quality. The best solution is to perform your first pass at the average quantizer you expect for 2nd pass. In this case that would have been a first pass at quantizer=3. This gives you very little quantizer fluctuation and thus a more consistent quality.

[aabxx]

Thanks for your good answer. :)