Rendered outcome two pass lower bitrate than source

[Norman Black]

Mainconcept AVC does not seem to be very accurate in hitting the average bitrate we specify. They are always under by some amount that varies by source.

A simple workaround is to have the average bitrate enough higher than the target average you want.

Sony AVC is much more accurate. Some say Sony AVC is CBR but looking at a bitrate graph shows it does vary but not by a lot.

Since your MAX and average bitrates are nearly the same you may as well eliminate the use of two pass and save the encode time. 1Mbps out of 30ish is not very much. The only reason for two pass is to allow the encoder to use widely varying bitrates depending upon scene complexity and still get an average of some specified value.

[Darren Hugh]

Thank you so much for helping out once again. I’m having a few difficulties when rendering the final thing. When rendering in the setting above, I get this sort of sharpening flicker in a way. As you can see from the two pics below, the 2 pass render is kind flickering. I took a screen shot from the worst part. It mostly looks good, but im not sure if its looking better than the one pass render. However I seem not to get that type of flickering when rendering one pass.

One pass – VBR

Two pass – VBR

Ive tried rendering CBR as well, and there is no flickering when I do that. However, im not able to specify my CBR, ive only got different options, where I have to pick from 28 mbps or 50 mbps, which are the cloest to my source footage.

So as you say, im not sure if I see the benefiths of two pass for my rendering.. Outcome size might be slightly smaller, but quality wise im not sure if it looks better or not.

I just dont know if I should go with a CBR instead, as it gets rid of that flickering. Obviously file size is gonna get bigger though..

[Norman Black]

The flicker you talk about might be due to a low minimum bitrate MC AVC might be using. Incorrectly too low as some would say. We are not given control over the minimum bitrate. In one pass VBR MC AVC probably uses a different min bitrate.

MC AVC does not give us good control over CBR bitrates. We cannot enter a value and are stuck with preset bitrates. Just use one pass VBR so you can enter the bitrate you want. Also since your entered settings restrict variability (max close to average) you are trying to force CBR from VBR already.

MC AVC one pass VBR is probably a lot like Sony AVC. Variable bitrate, but with a tight variation range.

I use Sony AVC mostly, but as I remember, MC AVC one pass is much more accurate hitting your entered average bitrate than two pass.