VDub and two-pass actually encodes audio twice?

[Raga]

I notice that in the discarded first pass files VDub produces, the audio track is there in its entirety. I am then assuming that VDub encodes the audio on both passes? If this is the case, am I safe to just choose "No Audio" for the first pass, and only activate audio processing for the second? It seems like a waste to let the CPU spend time doing useless work. Not that it's a major save of time, but still some minutes saved.

Am I right, or am I terribly missing something?

[kschang]

The "two-pass" only applies to video, not audio.

[donnyj]

Yes, it is a waste (allbeit small) to encode the audio twice

[Raga]

The "two-pass" only applies to video, not audio.

I realize that. However, I see that the audio is also present in the first pass file that gets scrapped. This, to me, tells that the audio is simply encoded twice and the first encode is scrapped, which is redundant. I don't think VDub, doing the 2nd pass, extracts the audio from the 1st pass file and muxes it with the 2nd pass output.

[celtic_druid]

It only encodes the audio for both passses if you tell it to. No reason why you can't disable the audio for the first pass. Personally I would encode the audio seperatly, You can leave it out for the 1st pass and mux for the second.

[Raga]

Yes, I did exactly that - set the first-pass audio to "No audio".

How would you encode the audio separately? I mean, which software, and why would that make the quality better?

[celtic_druid]

Because ACM means CBR. Use HeadAC3he or BeSweet.