MeGui's pre-rendering job: Results in same quality from input source?

[Terranigma]

Hello, I was wondering about the pre-rendering option in MeGui--Would I get the same quality encodes if I decide to use pre-render to store a video for later use, instead of if i'd of chosed to encode directly from the input (.avs) source?

[Kurtnoise]

yes...same quality afaik.

[check]

exactly the same quality

[Doom9]

The main reason why you'd want to use a prerender job is for multiple passes with excessively slow processing chains (lots of filters).. the more maxed out your cpu core(s) is/are, the more will input decoding (decode, crop, resize) slow you down over all the passes.
If your source is complex (e.g. HD DVD / Blu-ray, HDTV) and may use an CPU intensive codec (VC-1 or even more with AVC), pre-render jobs also start making sense (you will need a potentially insane amount of space as well though), it can also make sense to do a prerender job.

For your average two pass DVD rip with no filters other than crop/resize, there's not much point to doing a pre-render job so the decision whether to do it or not really has to be done for each and every single encode.

[Terranigma]

OK, thanks for clearing that up guys, and yes, I planned on doing a pre-render due to slow scripts. Now I have one last question: How can I decode using avisource? I was only able to decode with ffdshow and ffmpegsource. :o

[check]

you need a valid vfw decoder. Try enabling items in ffdshow vfw decoder -> output -> codecs.

[Terranigma]

you need a valid vfw decoder. Try enabling items in ffdshow vfw decoder -> output -> codecs.
Oh yes, it's enabled under Huffyuv (which is why I mentioned ffdshow above :P), but it seems like the only way to get it to decode is by using directshowsource (very slow :mad:) or ffmpegsource(very fast :cool:). I guess i'll stick with the ffmpeg method for a workaround (since it seems like my only viable option.) :D

[ChrisBensch]

So, based on what Doom9 said, for my "slow to encode" HD material, a pre-render job would speed things up as long as I have the space? Right now my encoder box gets about 1fps on 1080p material. It's killing me! I've got a few spare boxes for setting up x264farm but I still want to make single box encoding faster too.

[check]

Without a pre-render job, your CPU does this:
1st pass: decode avisynth, encode x264
2nd pass: decode avisynth, encode x264

With a pre-render job, your CPU does this:
decode avisynth, encode huffyuv
1st pass: decode huffyuv, encode x264
2nd pass: decode huffyuv, encode x264