10 bit x264 compression...

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10 bit x264 compression...

Postby blaku92 » Fri Dec 21, 2012 6:03 am

Hey everyone. I'm not that much of a CLI/compression expert, but I do like to keep up with what's possible. I've got a few questions now that I've been getting back into the game lately.

1.) Why am I seeing 10-bit x264 encodings everywhere when we all know no one has the means to display it properly + bluray spec is strictly 8-bit.

2.) Assuming it's possible, what avisynth workflows allow for the best 10-bit to 8-bit downsampling?
Code: Select all
ConvertToYV12()
with FFMS2?

3.) If I made a 10-bit After Effects Graphics Animation project from scratch, exported it same as source (to maintain 10-bit color), and wanted the final encode to be 10-bit x264, what GUI/CLI would I need to look into. (I might finally be interested in learning a bit of scripting.. What's the scripting language called? Are there many kinds for different CLI's?) I always feel like a noob asking these kinds of questions and I want to get a better grip on compression theory/practice, so any and all links to sites that will educate me from the introductory stages to the advanced are appreciated.

Thanks!
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Re: 10 bit x264 compression...

Postby mirkosp » Fri Dec 21, 2012 6:43 am

1) Higher quality with lower filesize. It makes life easier and better both when encoding and when sharing the final encode.
2) Avisynth is only 8bit per se ─ there are workarounds to work 16bit internally, but for your concerns, just load with ffvideosource. By default it'll convert to yv12 by itself ─ assuming you use 10bit 4:2:0 input and avisynth 2.5.8, that is. Though this isn't much of an issue generally, since you're supposed to edit with DVDs and BDs (which are always 8bit, as you know and stated in your post) and do the filtering yourself to bring it to a higher bitdepth if you want to. So having a 10bit source dithered to 8bit in avisynth is a "problem" (it really isn't) only for those that use downloaded footage, as far as AMVs go. And it's not like the industry has to use avisynth, they just throw around prores files if then want 10bit (or HDCAM SR tapes if need be, mostly for shipping to foreign countries), which will hardly need to be filtered.
3) In order to load 10bit in afx, you'll most likely have to resort to prores or other codecs used in professional environments, since I highly doubt it supports h.264 with bitdepth higher than 8 (and in fact, I'm not even too sure how well it fares with subsampling other than 4:2:0, when dealing with h.264 input). Save yourself the headache and import and edit at 8bit. Currently the playback setups on pc dither back to 8bit anyway, even if you technically would have the means to view 10bit videos. As I already stated, 10bit at the current time is mostly being employed as a filesize-saving commodity.

As a side note, I'll point out to VapourSynth; it's still under development currently, so I don't suggest you to adopt it just yet, but keep in mind it's what we'll switch to in the future year or two, and that it has native support for varying bitdepths and other things.
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Re: 10 bit x264 compression...

Postby Qyot27 » Fri Dec 21, 2012 10:21 pm

blaku92 wrote:1.) Why am I seeing 10-bit x264 encodings everywhere when we all know no one has the means to display it properly + bluray spec is strictly 8-bit.

Because we all know that the means to display it properly is a PC. Historically, digisubs don't target standalones (and really, neither do AMVs, although with AMVs I've found only a handful of 10bit cases).

And the bitrate savings and less banding (or in a different way, that any debanding done by the script isn't thence wrecked by going back to an 8-bit compression format).




The next novel thing (barring sudden leaps into HEVC, which has been recommended by electronics manufacturers to support 10bit in consumer profiles) is probably going to be 12 or 14 bit. I'm not holding any particular hopes of it getting wider support than it currently does prior to the arrival and entrenchment of HEVC, though.
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