This IS the Avid L2: Re: [Avid-L2] QT Pro can add video to audio but not audio to video/ duration change after QT change?s

Thursday, June 11, 2015

Re: [Avid-L2] QT Pro can add video to audio but not audio to video/ duration change after QT change?s

OK - so you missed the part where when Avid adopted ProRes as native, you could mixdown to ProRes in MC, export Same As Source, and there would be zero gamma shifting. This was a watershed moment a few years ago, and life has been good on that front since.

FYI - gamma shifting happens on MC exports if you export using Custom instead of Same As Source. This has always been the case, most likely due to invoking the QT Exporter (the same one as the one in QT Pro, which is also why I never use Export from QT Pro, only Save As…).

On Thu, Jun 11, 2015 at 2:02 PM, bigfish@pacbell.net [Avid-L2] <Avid-L2@yahoogroups.com> wrote:

Yes it's the Export vs. Save As that causes the interleaved audio and the loss of Time Code. The duration differences are as you say a drop vs. non drop. If I remove the tc track QT Pro shows actual clock time duration. Still doesn't explain why I can add video to audio but not the other way around.

I did a mixdown test last night, but I didn't mix down to ProRes. In the past with all the gamma shift issues going to ProRes on Avid exports etc.... I found at that time a QT ref of the DNX Avid media would eport to ProResHQ iusing QTPro without any noticable video level shifts. That is based on ama linking to the resulting file back into Avid and looking at it on a scope. My understanding is the ama link bypasses the QT engine where those level/gamma shifts seem to occur. As a result of that and my impression that Avid didn't do a proper conversion to ProRes on export to a .mov I have maintained that workflow. The hitch now is the inerleaved audio is a problem. I've got it working now but it's time I should test out Sorenson to see if it will take the Avid QT Ref and generate a ProRes file with 12 mono stem audio tracks and keep the time code.

---In avid-l2@yahoogroups.com, <bouke@...> wrote :

The two durations is a typical DF / NDF difference.
Note that the file without TC has a display where the last two digits are NOT frames, but fractional seconds.
Taking that into account the match is perfect.

Now, your workflow sucks big time.
If you have one track with safe color limiter, and that spans the entire export, that's indeed almost the same as a mixdown.
If you export that sequence as QT ref, the resulting file has TC (the sequence TC)
If you do a 'save as' in QT pro, the TC track WILL be retained, no need for QTchange.

Apparantly you do NOT do a 'save as' in QTpro, but an export to ProRes. That would be the same as doing so from Avid, with Direct Out.
My whole routine was to avoid that. If your render settings are set to ProRes, and you do a QT ref export, then a 'save as self contained',
you end up with a Prores file AND TC.

Bouke

VideoToolShed
van Oldenbarneveltstraat 33
6512 AS NIJMEGEN, the Netherlands
+31 24 3553311
----- Original Message -----
From: John Moore bigfish@... [Avid-L2]
To: Avid L2
Sent: Wednesday, June 10, 2015 8:07 PM
Subject: [Avid-L2] QT Pro can add video to audio but not audio to video/ duration change after QT change?s

I have exported QT ref of the 12 channels of audio stems and then done a save as to get a .mov of 12 mono tracks of the stem. The duration of this file is 57:08:16. I then do a QT ref of the video which has mixed frame rates so I have to check mix down audio even though there is no audio on the sequence. The QT ref video .mov also has a duration of 57:08:16. Then I export to ProResHQ 422. The resulting self contained ProRes file shows a duration of 57:12:09 in QT Pro. If I then use QT change to add time code to the video file the duration changes to 57:08:16 which is the correct duration according to the original Avid sequence. Weird? If I then delete the time code track the duration goes back to 57:12:09.

If I ama the files back into avid they are all the correct duration. Now if I try to take my self contained audio movie with 12 mono stems and edit it into the video movie using QT Pro I get a duration error and it won't do it. If I instead take the video file and edit it into the self contained audio file that works. WTF? The resulting video married to audio file is in sync on looks correct when ama'd back into Avid. When will the weirdness end? I even tried to set a custom frame rate of 23.976 in QT Pro before exporting to ProRes but the resulting file exhibited the same behavior. I have a safe color limiter over the entire sequence which is rendered so it's media wise like a video mixdown.

I'm curious what Avid is doing under the hood that makes a QT Ref video file with mixed frame rates still need the audio mixdown box checked. There is no sound to mix down.

The only difference I can see to adding the video to the audio file is in the info inspector the audio mono tracks/channels are listed above the ProRes Video. I don't know if that has any implications down the line. I wouldn't think so, but clearly thinking isn't helping me out much.

John Moore
Barking Trout Productions
Studio City, CA
bigfish@...

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