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Old 21st May 2019, 22:52   #1  |  Link
Nailgun
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Is AV1 ready?

I'm embarking on a transcode project after copying 27 DV tapes recorded in DVCPRO.
Obviously, the compression on these standard def files is several generations out of date, and the 13-gig-per-hour file sizes are preposterous for the 720 by 480 resolution they deliver.
I want to put them into a format that's more efficient after doing some processing such as noise reduction and gamma correction. I'd like to choose the codec and container combination likeliest to be around and supported in, say, 20 years.
Googling around, it looks to me like a large portion of the industry has gotten behind AV1.
So, at this point, I'm feeling like AV1 (MKV) is probably the codec to choose. I did an FFMPEG encode using the "constant" quality setting, and it crunches a 50 MB DVCPRO file down to ~1.5 MB with an HVEC comparison at ~ 3 MB. That's shockingly small to the point where I wonder if I screwed something up.
I guess I'm wondering at this point whether it's still too early to begin this work? We still have no players with AV1 hardware decoders, and I wonder if anything that I encode now could end up being unreadable by whatever hardware eventually appears?
I'm less concerned with obtaining the smallest-possible file size than I am with long-term readability. I intend to keep the untouched originals in case I need to do a re-encode at some point in the future, but I'd like to avoid that eventuality ...
I guess the question is: Do you agree that AV1 has the best shot at longevity? And, if you do think that's the case, what signals do we need to see in the real world to provide some assurance that what we encode won't need to be re-done in a relatively short amount of time? How do we know when a new codec is stable enough to justify a big time investment?
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Old 21st May 2019, 23:07   #2  |  Link
ChaosKing
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H265 will also be playable in 10+ years. No need to waste time and energy for AV1 now as it is too slow now.
And it's not like old codecs like mpeg2, xvid/divx suddenly are not playable these days.

Depending on the recodings I would also keep the source files if possible. A external 4tb hdd is not expensive these days.

I would go with h265+mkv+flac +(forced (soft) subtitles with a date, turned out to be very usefull if rewatching it in X years)

Last edited by ChaosKing; 21st May 2019 at 23:11.
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Old 21st May 2019, 23:15   #3  |  Link
sneaker_ger
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I think H.264/AVC, H.265/HEVC and AV1 all will have long-term readability. There's free software to support them. AV1 is supposed to be patent free now, H.264/AVC should be in 20 years. But: AV1 is not the one codec to end them all. There will be AV2, H.266, EVC and more. And in the future KI might offer much better scaling, denoising etc. than we have now. So for very important content it's best to keep the unfiltered source data losslessly. E.g. encode to AVC lossless solely because it may be more readable than DVCPRO in 20 years. Then store copies redundantly in the cloud and other places.

Is AV1 ready? I don't really think so. Encoders are slow and probably not as fine-tuned as more mature ones like x264 or x265.
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Old 22nd May 2019, 12:40   #4  |  Link
birdie
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Any codec is the best in regard to longetivity as long as its source code is available.

If you're concerned about the future you should probably avoid using any lossy encoding mode or codec.
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Old 23rd May 2019, 03:09   #5  |  Link
Blue_MiSfit
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Sounds like you're going to do some post-production on these files.

I'd personally suggest keeping them in ProRes 422 HQ. This will actually be higher bitrate than your DV sources, but DV is a terrible format (4:1:1 or 4:2:0, non-square pixels, interlacing all required etc). ProRes is much more flexible and will keep 4:2:2 10 bit quality out of your NLE (important after you apply color adjustments).

If you MUST make them smaller (why oh why) then I'd suggest HEVC or AVC today, personally. Both are widely supported, and there are great free encoders and decoders. Export from your NLE into whatever its native format is (again, ProRes 422 HQ is often a great choice) then use a too like ffmpeg to encode very high quality lossy HEVC or AVC, preserving the 4:2:2 10 bit nature. For example:

Code:
High quality lossy 4:2:2 10 bit AVC encoding with x264
ffmpeg -i input.mov -c:v libx264 -crf 16 -preset superfast -tune film -x264opts keyint=15 output.mp4

High quality lossy 4:2:2 10 bit HEVC encoding with x265
ffmpeg -i input.mov -c:v libx265 -crf 8 -preset superfast -x265-params keyint=15 output.mp4
Play with the crf values (higher = more compression = smaller files). I found that for some fairly complex 24p content, using crf 8 for HEVC gave me ~8 Mbps average, which is a nice 3/4 reduction from DV. The same CRF value for x264 makes much larger files, but that's expected since the scales aren't aligned. In that case, CRF 16 gave me similar file sizes, but of course the HEVC version was higher quality.

Honestly though, at these file sizes just buy a couple hard drives and keep it in ProRes or whatever (just don't do post production and then re-export DV. Yuck!)
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Old 23rd May 2019, 14:21   #6  |  Link
mariush
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I'd say too soon for AV1

I'd stick to h264 and flac/opus for audio... 10-20 mbps for SD content should give you superb quality , around 6-8 GB per hour.
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