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skystrife 2007-07-06 16:24

VFR Question
I'm interested in encoding using VFR, but I'm very new to the encoding scene and I have no idea of how to go about it. I read the VFR thread in here, but it's mainly a guide of what to do if you encounter a VFR raw (which I just recently did). I'm curious about the most accurate way of creating a VFR encode from a CFR raw. Say, taking a 23.975fps raw and getting rid of duplicate frames in still areas and (if there are any) when the image is moving. I think if I do this I'll be able to squeeze out slightly higher quality video while keeping the filesize down. I'm wanting to do this to a HD raw in order to keep the filesize down to 233MB while still having quality somewhere similar to a crf-18 pass.

Harukalover 2007-07-06 16:47

Make VFR out of CFR?

You would use something like DeDup or mode 3 in Yatta. Both won't really decrease filesize that much and both put you at risk for softsubs playback if you decide to use them. Most modern codecs will compress duplicate frames fairly well.

Either you can let DeDup gather dup metrics and do it automatically. (Be careful with how high you set thresholds or you may lose non-dups)

Or you can do it in Yatta by decimating frames manually. (takes lots of time though)



martino 2007-07-06 16:52

So you have a CFR raw, and want to forcibly make it VFR? Using DeDup to remove duplicate/similar frames and output a matroska timecodes format will only give you and the rest of the team trouble. So, for that matter try Dup. It replaces similar/duplicate frames with exact duplicates, and from what I've been told a modern codec (like h264, XviD and such) can compress a such frames down to 8 bytes. So there you go, saves some bitrate which can be used in other areas where it's needed.

P.S. Just make sure to set a good threshold for Dup, otherwise it could end up replacing frames that you don't want it to (hint: show=true is your friend).

Edit: Harukalover got there first... :)

TheFluff 2007-07-06 17:47

Yes, don't use DeDup. Even its author, pengvado (also x264 developer) says it's pretty pointless and only creates a lot of extra work. Use temporal softening and/or the normal dup instead.

Nicholi 2007-07-06 20:28

Truly if the RAW already is CFR, best to leave well enough alone. You only use VFR to preserve motion because of differeing framerates. Dropping duplicate frames though as with DeDup has proven to have little effect on filesize which is really only the real reason to use it.

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