Hi,
I have heard editors say that video mixdowns significantly speed up the exporting process. I believe I have noticed this myself on occasion. However, when I have done them, I've also been told by other editors that they are not necessary and a waste of time. What is the truth? There doesn't seem to be a real consensus on this?
Yes massivlely.
If you do a video mixdown MC will use more (if not all) cores and make new media very quickly.
The export process is then basically a file copy and not limted by the QT back end that throttles access to cores.
If you do an export and transcode at the same time without a video mixdown then the codec conversion is handled by the 32 bit legacy QT engine. Worse than that the resultant content isn't available to MC so a subsequent export will have to re-do it all again.
Many editors will video mixdoen and build an export sequence from that. Any fixes are then done by going back to the pre mixdown seq. Make the fix, do a short video mixdown of that section. Cut that into the main video mixdown export seq and re export.
Way Way Way faster. Works really well for AS-11 exports that need AVC-I media.
Broadcast & Post Production Consultant / Trainer Avid Certified Instructor VET (Retired Early 2022)
Still offering training and support for: QC/QAR Training - Understanding Digital Media - Advanced Files * Compression - Avid Ingest - PSE fixing courses and more.
Mainly delivered remotely via zoom but onsite possible.
T 07581 201248 | E pat@vet-training.co.uk
Great, Pat. Thanks for the detailed explanation!
I don't believe a video mixdown is any faster than a full sequence render, though. And same-as-source exports from either a sequence with zero effect or with all effects rendered or one with a mixdown should all be equally fast. The advantage of a rendered sequence — compared to a mixdown — is the ability to make changes to it, then render the changes and export.
Job ter Burg: I don't believe a video mixdown is any faster than a full sequence render, though.
I don't believe a video mixdown is any faster than a full sequence render, though.
add to this that renders can be done in the background whilst editing , nothing you can do with mixdowns.
Using BG renders all the time here, when edit is done, so is the project
Tomas
Good to know, Job.
And then get your same as source sequence out of Avid and use FFmpeg to encode to your desired QT format - significantly faster and in the case of H264, significantly better results.
mark.burton:use FFmpeg to encode to your desired QT format
Indeed! Have to say though, FFmpeg is pretty fantastic :-)
Back ground renders can be very useful. But the advantage a video mixdown offers is a single MXF media file of that video plus a master clip you can use. Renders are much harder to "manage"
Also with renders you have to have an effect or use a submaster effect to force MC to make media.
As a comparrison I've just taken a 4:49 sec H264 source file.
A Z400 3.07GHz Quad core 12GB RAM using internal media RAID.
Foreground Render to DNX185x (using sub master effect) 3:15 mins
Background Render (priority normal but no foreground activity) 5:49 mins
Video Mixdown 2:37 Mins
So compared to a background render (and don;t forget back ground renders pause while MC is busy) a videomixdown was twice as fast. Even the foreground render took longer. Not much on a 5 min clip but make that an hour long timeline and your time till you get home to bed starts to drag out....
Pat, your example is confusing, as you are not just 'rendering' but transcoding.
I'm talking about a sequence with MXF media generated from the get go. Cutting, adding effects, some of them realtime, then before export, you either render the whole thing, or do a video mixdown. The resulting Same-As-Source export is equally fast. Whether the mixdown or the render is faster also depends on the amount of non-rendered effects.
Having your final version mixed down to a master clip (although without the sound unless you mix that down and AutoSync) can be an advantage in certain workflows. If at any point you want to change anything, the mixdown is not as flexible as the rendered sequence.
IMHO no method is superior, depends on workflow and project. Video mixdowns are not the end-all for every workflow. And neither are rendered sequences, of course.
P.S.: just did a test. 2-minute sequence consisting of DNxHD clips, each of them with a source-side color correction, save for one. Render in-out took 29 seconds. Video Mixdown (to the same flavor of DNxHD) took 26 seconds.
If you make an export sequence using your video and audio mixdown and need a change you go back to your pre mixdown seq. Make the change. Mixdown that section and cut into the export sequence. Then you still have a fast SAS export route.
If you aren't transcoding and just rendering with the same codec I'd expect speeds to be similar (background will always be slower).
We find video mixdowns a massive timesaver for AS-11 exports.
Pat Horridge: If you aren't transcoding and just rendering with the same codec I'd expect speeds to be similar
If you aren't transcoding and just rendering with the same codec I'd expect speeds to be similar
My point exactly.
Two small point to add when considering full render vs. mixdown.
I just did a job with Canon C300 source material that was consolidated. So, full Avid media. But XDCam Long GOP. My sequence was then edited with renders set to be DNx220. Some clips had no effects or color correction - so never had a render associated.
Doing a QT reference would not work, as the native XDCam footage shows up black. So I would have to "manage" my sequence by doing phantom renders just to create media visible to a QT reference workflow. Depending on the sequenc complexity, a mixdown might be easier.
Another thing to consider if a Same As Source export is the same goal, you want to make sure that the sequence is one codec type for source and renders. A mixture of codec types can cause issues. And I rarely have the luxury of a single codec type.
As noted, there are many things to consider. Forewarned is forearmed.
Jef
_____________________________________________
Jef Huey
Senior Editor
I tried to mixdown a 5 minutes film shot as RGB 444 1080p 23.98p with heavy BorisFX applied to the entire video and took hours to render as RGB444 using a transcode as RGB 350x 444 ....later a single fade fix did unrender the entire top layer with the BorisFX...more hours to render...this time rmixing video as Rec 709 and windows shows another hour of waiting...
Mixdown video is not allowed when project is RGB 444 (Even the 1920x1080p menu is gray out) but if I change it to Rec 709 video mixdwon is allow. Is this normal? I understand video mixdown can be quicker and you may be able to do 2 things at once: render all effects and mix video in one strike. I tried collapsing all and render but the render will never end this way, it didn't make any difference. It shouldn't I am just collapsing but what is the best way to work in shorts with heavy effects and a computer that is OK but not the fastest? Is it time to recycle this Mac in order to work with RGB 444 (Shooting green screen) footage?
I wish Avid would offer guidence on these issues.
MacPro 2011 2.8ghz quad core intel , 32GB 1066 MH DDR 3, ATI Radeon 5770, OSx 10.9.5, MC 8.4, rendering-editing to an internal SSD drive Sata 7200 rpm.
© Copyright 2011 Avid Technology, Inc. Terms of Use | Privacy Policy | Site Map | Find a Reseller