Audio distorted static when retiming on export AAC

A colleague rendered a 24fps retimed H264 file with AAC audio from a 23.976 project timeline and the audio was full of static and distortion and completely unusable. This is v18

So I tested this myself on a completely different system and found the same with newest download v18.1.4

** The problem with static only occurs if the rendered file is AAC compressed audio with the frame rate different than project.
No static occurs on Linear PCM audio render - even with retime.

This ONLY occurs if rendering to a "retimed" frame rate.
So rendering to 24fps in Deliver from a 23.976 Timeline/project


- Chris Lundy

Resolve 18.1.4 MacOS 12.6.3 iMac 5K Retina 27" 2017

Resolve has suffered for years with phasing issues when audio is retimed, whether during fast playback or during export.

But I've never experienced static as a result.

I don't think this is phasing causing this to sound like this ---
---as I said it ONLY happens when the retimed export is using AAC compression for the audio track.

This should be an easily repeatable bug with straightforward steps.
Put a 23.976 ProRes clip with audio on a Timeline and export to Deliver result that is 24 fps.
If you do 24fps H264 with AAC audio it will sound bad and distorted, over modulated and full of static.
Do it again as a 24fps ProRes with Linear PCM it is fine.
I even did a WAVE as Linear PCM at 24fps and that is also fine.
*The problem is the AAC codec WITH the retime.

And with Resolve containing Fairlight code I'd expect a better result and not to see this type of issue.

- Chris

I recently did a large project just like that. 23.976 clips all re-timed and delivered to 24 with AAC audio.

There were a few phasing issues as mentioned, bot no static whatsoever.

Jim may I ask what version of Resolve you had success on with that and if you are on Mac or PC ?

My current issue is on Mac with v18. I even downloaded the newest 18.1.4 on a "home" iMac to test and got the exact same result.

That was completed in Studio 18.1.3 on Windows 10.

I went back and tested on old systems at my facility. I'm talking v15 and v16 running on older MacPro hardware. BOTH rendered clean audio in an AAC track. Same exact workflow.

So this is clearly a bug on v18 on Mac.

How would this be best sent to Blackmagic to look at this issue?

Simple 23.976 stereo timeline with a ProResHQ source with embedded stereo audio
Deliver to H264 with AAC audio (128Kbps example) @ 24fps (so system retimes)
Audio set to Timeline Track or Bus since both are stereo.
Rendered H264 will sound like static with hints of the audio under it.

How would this be best sent to Blackmagic to look at this issue?

This thread.

I'm having what seems like the same issue. My project sounds great, but the exported file is just noise. I'm running Mac OS 13.3.1 with DaVinci 18.1.4.

This never happened before. My clips are 23.976 frame rate as is the project and the render setting. Is there an easy fix? I've been trouble shooting all morning.

UPDATE: I changed the Project Settings and the Render Settings to 24fps and it solved the issue. My camera is recording at 23.987, but for the audio to sound correct it seems like DaVinci has to be set to 24fps. I don't recall this being the case in previous versions.

Both frame rates normally work just fine, Steven. You've got a system issue there.

Both frame rates normally work just fine, Steven. You've got a system issue there.

Nope. It's happening to me also on v18. Which begs the question: WHY is the default framerate 24fps?????? Are there a lot of people posting films for a filmout? I doubt it. I sometimes forget to change the framerate to the almost universally used 23.976 and then THIS happens, ugh. Major pain in the as.s

WHY is the default framerate 24fps??????

Hollywood.

It's happening to me also on v18.

But it's not normal. It's either a System issue, or maybe a media issue.

If every Mac user had this problem, this thread would be dozens of pages long.

Are you able to create and share a one clip Archive (.dra) that shows the issue?

If it's a bug, it wouldn't necessarily happen for all mac users. I figured out a way around it. Main thing is I need to remember to reset the asinine 24fps framerate to the proper 23.976.

24fps is the proper frame rate for electronic production for the cinema. It is also the framerate used when transferring film to digital from a telecine. As first and foremost DaVinci is the grading application used for both, this is why the default is 24fps.
29.976 like 25, 50, and 60 are purely video framerates.