ASK & DISCUSS INDEX

9 years ago - Paddy Robinson-Griffin

XAVC is just an MPEG4 profile, and MPEG streams don't generally like being messed about with. If you're planning on doing lots of fine cuts, effects, pushing the grade, etc., then it's probably better to use an editing codec. I don't know about Cineform specifically, but for Avid you'd use DNxHD, for instance.

9 years ago - David Lane

Hi Paddy thanks, I am transcoding a few day's worth of footage into DNXHD to see how it compares in Premiere.

Many thanks :)

9 years ago - Paddy Robinson-Griffin

Hi David, is Premiere able to use DNxHD? I don't know, but go with whatever the Premiere native editing codec is, if there is one (or at least do a 30 sec tech test before a big transcode!)

9 years ago - David Lane

I am fairly certain it is, away from my desk atm but will report back. It'd be weird if it didn't considering adobe media encoder is the one doing the process!

9 years ago - Paddy Robinson-Griffin

Let us know - and if Premiere uses it NATIVELY (or there's no point if it's going to transcode again on ingestion!).

If it will use it natively, then the DNxHD bitrate and colour depth will be driven by your requirements (do you need 10 bits/channel? 12 bits?) balanced against disc space. Fortunately that's dirt cheap these days, but if you are transcoding a lot, look at SSD's and USB3 for interchange.

9 years ago - Paddy Robinson-Griffin

PS, 8 bits/channel gives you 2^(8*3) = 16.8M colours, 10 bits gives you a billion or so, and 12 gives you 68Bn colours. Frankly I'd be impressed if anyone here can resolve more than 16.8M, but 10-bit gives you a little extra heading latitude, especially the greens, I imagine.

9 years ago - David Lane

Alrighty! We have lift off. Premiere accepts DNxHD 1080p HQX 10-bit. My FS5 is 4:2:2 in 10bit so yeah and the file size isn't too bad! My hard drive is holding up and can play back no bother even with a bit of light Lumetri work. Thanks Paddy, appreciated your work :)

9 years ago - Paddy Robinson-Griffin

That sounds good - especially if you can stay in DNxHD the whole workflow right up to delivery for DCP. No post facility is going to be unable to use it, although it's with checking container formats as well as codec. MXF should be fine/ideal

9 years ago - David Lane

Definitely! Very pleased. The container is MXF so all good! I know what this weekend will entail... transcoding all the rest! Then batch renaming... Thanks again.

9 years ago - James Bayliss-Smith

No need to transcode. You cannot Improve footage from original codec all transcoding looses quality, if you don't need to transcode then don't until you need to (at the end)

9 years ago - Paddy Robinson-Griffin

Not all transcoding loses quality. Lossy compression loses quality, sure, but there's nothing inherent in transcoding to lose it. And I agree that you cannot create quality where none exists, bit you can preserve it better editing and grading in some codecs compared with others.

The MPEG family of codecs are designed to be very lossy. They're highly compressed and ideal for distribution, not editing/fx/colouring/any circumstances where they're being pushed beyond their ideal- exhibition. They have long GOP (to achieve the compression), so a cut during that group means the other frames either side have to be recalculated and rasterised (P-frame created that didn't exist), so each edit with MPEG format video is in fact a mini transcode using lossy codecs. Add an effect and it's the same again, grade same again. The transcodes are cumulative, quality is diminished.

If instead you go to an editing codec like DNxHD, it's much more akin to just a long string of P-frames, so there's little/no temporal interdependence, so they better preserve quality as the file is worked. Having an increased bit depth per colour means banding isn't inevitable when colouring a gradient, nor does adding titles introduce mosquitoes. You're using the right codec for the job.

The very final stage in the lifecycle is to go to DCP, which is a JPEG2000 set - every single frame rasterised (with internal, but no temporal compression). MPEG codecs are incredibly clever and cram a lot of visible picture into a very limited bandwidth, but to do so comes at a cost. They're fine, brilliant even, for consumer and prosumer cameras acquisition, but it's not meant for professional quality work. Greatly convenient for ENG, not meant for drama finishing in a DCP. And of course, excellent at what they're meant for, exhibition to humans, where you only want to mathematically throw away detail at the last possible moment.