Avisynth first pass settings

[foxyshadis]

I'm not sure which forum this goes in but I'm going to take a stab and put it here.

Is there any way for a host application (vdub, megui) to signal avisynth that it's doing a first pass? Say, by defining a variable in the script's global context. Vdub has its 'video analysis pass' and megui has 1st/2nd/3rd built right in of course. (Or is x264 the host for avisynth in megui? I'm not sure.)

This way a script could use something like "IsFirstPass ? CpuStuff() : last" to disable the really slow filters. I understand that this could throw off the stats if used incorrectly, but in general I just want to use it for really slow denoise filters; especially with x264/xvid turbo on it shouldn't change enough to make a big difference in the final output. Of course there'd have to be a IsFirstPass=default(IsFirstPass,false) at the top of the script for those that don't support it.

Basically just a shortcut for keeping two separate scripts at encode time right now.

I don't know, is this useful at all?

[Poutnik]

There is better way if there is enough disk space.
For slow filtering it is faster to filter to intermediate file,
and than perform 2pass for that file.

[foxyshadis]

Well yes, that's another solution. (Debatable whether it's "better" or not.) I just hoped to avoid it because I'm already working from a huffyuv file (well, msu), two just means twice as much space for the movie. ^^;;

[Didée]

I'd go for the simple methods. Use the "'#" sign, and/or a copy of the script for batch processing.
(Assuming you've enough disk space left to make a copy of the avisynth script :D )

[movax]

I'd go for the simple methods. Use the "'#" sign, and/or a copy of the script for batch processing.
(Assuming you've enough disk space left to make a copy of the avisynth script :D )

Yep, a simple method I have used many times to poke at pass differences, or get some effects I wanted in. Just make script.1stpass.avs and script.2ndpass.avs.

[Poutnik]

I'd go for the simple methods. Use the "'#" sign, and/or a copy of the script for batch processing.
(Assuming you've enough disk space left to make a copy of the avisynth script :D )
Could not this bring difficulties to bring troubles to Xvid to keep target size at 2nd pass ? One adviced me before to replace slow filter chain for 1st pass
by sth like blur(x), where x should be chosen to simulate similar compressibility
to original excellent, but slow filtering.....

[Poutnik]

Well yes, that's another solution. (Debatable whether it's "better" or not.) I just hoped to avoid it because I'm already working from a huffyuv file (well, msu), two just means twice as much space for the movie. ^^;;
For me MSU is quite slow for intermediate files. I as w98se user need to cut my captures in 4GB cuts,
so I can in case of need process them one by one :-)