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Audio Crackle in standard mp4 render

PostPosted: Tue Sep 10, 2019 8:45 pm
by James Moore
Version 16.1.08.025

I have a project using no VST's, simply a stereo audio track suppled by the Sound House.

I rendered a standard BEST quality MP4 (on a windows box) using the H.264 codec and audio at default settings - AAC 192Kb/s

The audio had crackles occasionally that weren't in the original.

I see others have had a similar problem. Is this a beta issue? Is it across all codecs, even uncompressed?

Re: Audio Crackle in standard mp4 render

PostPosted: Tue Sep 10, 2019 11:12 pm
by Charles Bennett
Never had any crackling here. If you are talking about The Sound House in London I know them well. They would never put out a track with crackling on it.
Is it a crackle as in a loose connection, or distortion? What levels are your meters showing? Does it always happen in the same place?

Re: Audio Crackle in standard mp4 render

PostPosted: Tue Sep 10, 2019 11:59 pm
by James Moore
sorry, not the Sound House, just a sound house, but, yes, the wav file they sent me is fine. It plays back on the Resolve timeline just fine but the mp4 render of the timeline had a number of audio crackles that weren't in the original. It sounds kind of like a compression artifact...

My observation that I'm not alone came from this thread:

viewtopic.php?f=32&t=98469

Re: Audio Crackle in standard mp4 render

PostPosted: Wed Sep 11, 2019 2:50 pm
by James Moore
I ran some tests on this project and the mp4 renders.

I did a second render of the timeline - same settings.

No, the crackles do not happen at the same place but they did occur in the second render. They don't happen very often but they do occur. This particular project is 19 mins. long and the first crackle that was obvious to me was at the 15 min mark the second time around. The first render had one at the 1 min. mark and another at 11:26 and another at 12:19 (my client noticed them and sent the notes). I am not that familiar with the sound on this project so I missed them when I proofed it but they are there, definitely, and not in the original.

Another thing that occurred on the second render is the overall audio level is higher, by about 5 db. Nothing changed in the project between the two renders.

I think there is definitely bug action going on here.

Re: Audio Crackle in standard mp4 render

PostPosted: Wed Sep 11, 2019 2:55 pm
by Jim Simon
I haven't had this issue myself. Perhaps a look at the audio hardware and settings is in order.

I wonder if anyone having this problem is using a USB audio device?

Re: Audio Crackle in standard mp4 render

PostPosted: Wed Sep 11, 2019 3:09 pm
by James Moore
The audio device shouldn't matter when rendering one would think. In my case I am using a Blackmagic Mini Monitor.

Re: Audio Crackle in standard mp4 render

PostPosted: Wed Sep 11, 2019 3:12 pm
by Jim Simon
James Moore wrote:I am using a Blackmagic Mini Monitor.


That seems like it's just for monitoring, it doesn't actually process the audio during exports like a Focusrite Scarlett does.

Re: Audio Crackle in standard mp4 render

PostPosted: Mon Sep 23, 2019 7:33 pm
by Tony Hailstone
I'm having same issue. Random audio blips, only a few times over an hour, but noticeable and not in the same place when re-rendering. Settings MP4 1080P NVENC Best. Audio AAC at 192kbps. Using 16.1 Beta 3 Studio.

Re: Audio Crackle in standard mp4 render

PostPosted: Mon Sep 23, 2019 11:19 pm
by Roen Davis
Yes, I rendered an mp4 yesterday and had crackle that was not in the original wav. 16.1B2
I hope this can be solved ahead of my delivery...
*Nvidia option.

Re: Audio Crackle in standard mp4 render

PostPosted: Tue Sep 24, 2019 5:46 am
by benoit
I have some random crackle too, on mp4 render

Re: Audio Crackle in standard mp4 render

PostPosted: Tue Sep 24, 2019 5:03 pm
by James Moore
If the engineers are having trouble replicating this problem an easy way to do it is to place approximately 20 mins of 1k tone on the timeline peaking at -10db, color bars for video (make compound clip - in order to un-grey 'add to render queue') and render at default setting for MP4 h.264 codec Native encoder, Best, and Audio AAC at 192Kb/s

Instead of having to sit and listen for the crackles you can see it easily enough in the waveform. There is a fair bit of noise introduced throughout the render.

Re: Audio Crackle in standard mp4 render

PostPosted: Wed Sep 25, 2019 6:31 pm
by kalpox
Not only in mp4, I'm having this issue in other formats too. To me this is a critical bug that cries out for a hotfix. DR is just unusable.

Re: Audio Crackle in standard mp4 render

PostPosted: Thu Sep 26, 2019 4:54 pm
by Tony Hailstone
I've done a test as suggested using a 1khz tone, then did a bog-standard MP4 render at Best Settings and NVENC. I then put the rendered file back into the same timeline so I could compare the two waveforms side-by-side. The result was shocking. Much noise is introduced into the render, so much so that Resolve can no longer be considered for professional work. This definitely requires a fix. I will downgrade until it is.

Please see attached waveform comparison. You may need to zoom in to see the noise introduced from the render.

16.1 B3 Sound Bug.jpg
16.1 B3 Sound Bug.jpg (171.52 KiB) Viewed 6676 times

Re: Audio Crackle in standard mp4 render

PostPosted: Fri Sep 27, 2019 2:48 pm
by Charles Bennett
You must remember the amount of compression being applied to the tone. By way of comparison here is a 1khz 24bit 48khz -10dbfs broadcast WAV next to the same file bounced to 24bit 192kbps mp3. Both were done in Pro Tools. You can see the noise and compression artifacts introduced into the mp3.

Re: Audio Crackle in standard mp4 render

PostPosted: Fri Sep 27, 2019 3:17 pm
by James Moore
While the noise may be normal and mostly inaudible the random 'crackles' are not. These appear in the waveforms separate and distinct from those noted noise items. I am away from my computer so I can't post a picture of the crackle until Monday.

Re: Audio Crackle in standard mp4 render

PostPosted: Tue Oct 01, 2019 7:37 am
by Tony Hailstone
I'd echo what James says. The general bumpy waveform is largely unnoticeable when playing back, however, the spikes that are pointed out are very evident and sound like a crackle, albeit briefly, but ruins whatever it happens over.

Re: Audio Crackle in standard mp4 render

PostPosted: Tue Oct 01, 2019 7:41 am
by Reynaud Venter
James Moore wrote:While the noise may be normal and mostly inaudible the random 'crackles' are not
Most likely quantisation artefacts from the lossy data compression scheme.

Re: Audio Crackle in standard mp4 render

PostPosted: Tue Oct 01, 2019 12:04 pm
by Joheck
I have the same problem: Crackles once in a while over the whole rendered film (45 min.). Not only with aac-codec but also in PCM format. Tried to export the single tracks as aufio files didn't solved it. (16.1 Beta 3 Studio)

Re: Audio Crackle in standard mp4 render

PostPosted: Tue Oct 01, 2019 2:03 pm
by James Moore
I hope the Blackmagic engineers are aware of the issue and aren't rationalizing it. It is a problem.

I have attached an image of the rendered file under the original. The tall spikes represent a 'crackle'. I have also attached a zip file of a wav render (can't attach a wav) so one can hear the crackle as well If one wants. You can also hear my tone loop point shortly after the crackle.




Crackle-1.jpg
Crackle-1.jpg (110.81 KiB) Viewed 6562 times

Re: Audio Crackle in standard mp4 render

PostPosted: Tue Oct 01, 2019 2:23 pm
by Reynaud Venter
Perhaps isolated to the Windows platform, as I am unable to reproduce on macOS neither with AAC nor with Broadcast Wave, nor MXF. Deliverables are within spec.

Re: Audio Crackle in standard mp4 render

PostPosted: Tue Oct 01, 2019 3:33 pm
by Charles Bennett
Do you get the crackling if you reduce the render speed to 50%?

Re: Audio Crackle in standard mp4 render

PostPosted: Tue Oct 01, 2019 4:08 pm
by James Moore
Charles, how do you reduce the render speed? I don't see anything obvious in the interface.

Reynaud, that is an interesting observation regarding Mac OS vs. Windows OS. It might have something to do with NVIDIA - I just tried an mp4 render and instead of using the "Native" encoder I tried the "NVIDIA" encoder and there appeared to be more frequent crackles in the rendered MP4 file.

Re: Audio Crackle in standard mp4 render

PostPosted: Tue Oct 01, 2019 7:25 pm
by Joheck
James, in order to reduce render speed you have to go to the file section in the render settings.

Re: Audio Crackle in standard mp4 render

PostPosted: Tue Oct 01, 2019 9:12 pm
by James Moore
Hi Charles,

I ran a render at 50 and one at 100 and neither exhibited the crackle. I did another under the same conditions set to Max and the crackles are back.

I read the manual re: Render Speed and it just talked about SANs and multi-users. Nothing that would suggest to me it would affect the content of the render. I scratch my head wondering what made you think of that option but it certainly does seem to be the issue.

Re: Audio Crackle in standard mp4 render

PostPosted: Tue Oct 01, 2019 10:04 pm
by RCModelReviews
Reynaud Venter wrote:Perhaps isolated to the Windows platform, as I am unable to reproduce on macOS neither with AAC nor with Broadcast Wave, nor MXF. Deliverables are within spec.

Based on BMD's response to the jumping number-box issue (which is versions old and only affects Windows machines) we'd better hope this isn't a Win-only issue. One can't help but get the feeling that Windows is a "barely supported" platform in respect to some long-standing and incredibly annoying problems.

Re: Audio Crackle in standard mp4 render

PostPosted: Tue Oct 01, 2019 10:35 pm
by Roen Davis
Same thought going through my mind, RCModelReviews!
I think the numerical entry issue is across Linux too from what has been said.
This crackle and pop might be Nvidia? RTX?
I know the dev gurus will be escalating this in the same way that the numerical entry fix is imminent!

Re: Audio Crackle in standard mp4 render

PostPosted: Wed Oct 02, 2019 1:15 am
by JustinJohnson
Roen Davis wrote:Same thought going through my mind, RCModelReviews!
This crackle and pop might be Nvidia? RTX?


Just removed my nVidia 970 which was getting TONS of clicks on 5.1 audio export and put my AMD 570 back in.. All clicks are gone now.Sometimes I could get it to export without clicks with the 970... and it would only ever click on 5.1 export... will keep testing.

Re: Audio Crackle in standard mp4 render

PostPosted: Wed Oct 02, 2019 9:45 am
by Charles Bennett
Crackles like those in digital audio are normally caused by buffering issues. This could be caused by the media you are writing to, ie if it's a spinner, the disc is very full or it has a low spin speed. The bottleneck could be somewhere else, or it could just be the amount of processing being done for that particular video.
As I use 7200rpm spinners in my system I always render at 50% speed. Yes it takes longer but so far this has meant I have not seen any problems when rendering 4k.
I have noticed that when editing a piece that is borderline for my GPU, the first thing to suffer is the audio when playing in real time.

Re: Audio Crackle in standard mp4 render

PostPosted: Wed Oct 02, 2019 1:34 pm
by James Moore
While I can understand that disk speed would affect real time playback and that 'crackles' would be a likely outcome if the system can't keep up but in this case we are talking about rendering a file to disk. A slow disc shouldn't affect the render at all. In this case I am rendering color bars and tone at 1080p to a raid array. A render done at 100 (I presume 100%) yields no crackles but a render done at 'max' has crackles. That suggests to me this is a bug and not a 'reasonably expected' performance issue.

Re: Audio Crackle in standard mp4 render

PostPosted: Wed Oct 02, 2019 1:46 pm
by Gary Hango
Maybe the “Max” setting uses a different rendering process than 100 and lower. Possibly some sort of direct streaming process similar to real-time but at a higher framerate. 100 and lower using a normal buffered rendering process.

Re: Audio Crackle in standard mp4 render

PostPosted: Wed Oct 02, 2019 1:54 pm
by benoit
and that could explain why the problem occur with Nvidia card because with nvidia the rendering is much faster in MP4.

Re: Audio Crackle in standard mp4 render

PostPosted: Wed Oct 02, 2019 2:01 pm
by James Moore
At the very least Blackmagic folk should not have the default setting as 'Max' if it has the potential to yield unacceptable results.

I still can't wrap my head around a render pipeline yielding crackles - real time playback, sure, but a render? 'Max' should imply it goes as fast as it can given the hardware circumstances but not as fast as it can even if the rendered file is broken.

Re: Audio Crackle in standard mp4 render

PostPosted: Wed Oct 02, 2019 2:35 pm
by Jim Simon
James Moore wrote:'Max' should imply it goes as fast as it can given the hardware circumstances but not as fast as it can even if the rendered file is broken.


That! Definitely.

An export should never proceed past a lack of data. Which makes the entire concept of limiting export speed an odd 'feature' to include in an NLE.

Re: Audio Crackle in standard mp4 render

PostPosted: Thu Oct 03, 2019 1:51 am
by Gary Hango
If I’m not mistaken, this crackling only occurs when you have an Nvidia card installed. Has this been confirmed? I’ve seen in other forums complaints about noise in Protools when a Nvidia card is installed. Seems like more than a coincidence. Has it been confirmed that this only happens when the Max setting is used along with hardware encoding? Has a nonstudio user observed this? In other words, if you don’t use hardware encoding, is the crackling still observed in the exported file?

Re: Audio Crackle in standard mp4 render

PostPosted: Thu Oct 03, 2019 4:01 am
by JustinJohnson
Gary Hango wrote:Has it been confirmed that this only happens when the Max setting is used along with hardware encoding?


I got crackling no matter what the setting was at..max ..50...75...made no difference..once I replaced my nvidia 970 with ati 570... crackling is gone.

Re: Audio Crackle in standard mp4 render

PostPosted: Thu Oct 03, 2019 4:06 am
by Roen Davis
So maybe it has to do with nVidia cards but crackle is new and the nVidia cards are not.
I have an RTX 2080 TI and the crackle I have experienced has only been since 16.1 thus reducing the likelihood that it is inherent in the hardware...

Re: Audio Crackle in standard mp4 render

PostPosted: Thu Oct 03, 2019 8:11 am
by ChipKng
Are you guys using the latest version of the nvidia driver? Which type? WHQL cert, GRD, SD,QNF, ODE or Beta?
As it seems only nvidia cards are suffering from this problem then I suggest to go back for older version of the driver (if you have enough time to test).

Re: Audio Crackle in standard mp4 render

PostPosted: Thu Oct 03, 2019 10:01 pm
by Roen Davis
431.86
It’s a good thought.

Re: Audio Crackle in standard mp4 render

PostPosted: Fri Oct 04, 2019 10:56 am
by ChipKng
Roen Davis wrote:431.86
It’s a good thought.


They just released a 436.51 WHQL driver. Can you give it a spin?

Re: Audio Crackle in standard mp4 render

PostPosted: Fri Oct 04, 2019 11:34 am
by ChipKng
ChipKng wrote:
Roen Davis wrote:431.86
It’s a good thought.


They just released a 436.51 WHQL driver. Can you give it a spin?


I just noticed the studio driver remains 431.86. Maybe it worth to try the non-studio driver.

Re: Audio Crackle in standard mp4 render

PostPosted: Fri Oct 04, 2019 2:58 pm
by Jim Simon
ChipKng wrote:Are you guys using the latest version of the nvidia driver?


I'm using Studio 431.70 without any audio issues.

I also don't use NVIDIA encoder for deliverables, as hardware encoding has a very long history of being inferior to software encoding.

Re: Audio Crackle in standard mp4 render

PostPosted: Fri Oct 04, 2019 3:11 pm
by Jean Claude
ChipKng wrote:Are you guys using the latest version of the nvidia driver? Which type? WHQL cert, GRD, SD,QNF, ODE or Beta?
As it seems only nvidia cards are suffering from this problem then I suggest to go back for older version of the driver (if you have enough time to test).


Is HDD source clips also used as destination HDD on the Delivery page?
(I am with Windows 10 + V16.1b3+ Nvidia GPU with NSD 431.86 driver and never had a crackle in an MP4)

Re: Audio Crackle in standard mp4 render

PostPosted: Sun Oct 06, 2019 12:30 pm
by RaphaelCarpenter
Same crackle noises here in random places in Export, whatever I'm using DNXHR, h.264, PCM, ACC
For now DR is useless for any work I'm afraid :(
Config: i9 9900, 64GB, RTX2080Ti, NVME m.2 970 PRO ... so please don't even try to suggest it's not enough for DR :)))))))

Nothing like this happen before I was using DR for last 2 years and this is 1st time I feel disappointed and pissed off

...or BMD wants me to use DR for video rendering only and then use another software (Premiere, Avid, FCP) to render final video with proper audio track ?

This is critical bug, I'm going to produce TV Commercial for big brand next week...not sure DR will be involved in this one :(

Re: Audio Crackle in standard mp4 render

PostPosted: Sun Oct 06, 2019 12:35 pm
by Roen Davis
What nVidia driver are you running, Raphael?

Re: Audio Crackle in standard mp4 render

PostPosted: Sun Oct 06, 2019 2:22 pm
by RaphaelCarpenter
Studio Driver 26.21.14.3170

Re: Audio Crackle in standard mp4 render

PostPosted: Sun Oct 06, 2019 2:52 pm
by Jim Simon
I just exported a 90 minute film to MP4 and no audio issues at all.

I did not use the NVIDIA encoder, I used the NATIVE.

I do not have any USB audio in the chain.

Those are two factors I still think folks should be looking at.

Re: Audio Crackle in standard mp4 render

PostPosted: Sun Oct 06, 2019 4:42 pm
by John Paines
Crackling on exports occurs with other formats, as related threads here and on the main board attest, from a variety of users.

Good to hear not everyone has encountered it. But the issue remains.

Re: Audio Crackle in standard mp4 render

PostPosted: Sun Oct 06, 2019 4:59 pm
by Jean Claude
John Paines wrote:Crackling on exports occurs with other formats, as related threads here and on the main board attest, from a variety of users.

Good to hear not everyone has encountered it. But the issue remains.


Surely John.

But as it is to hard to reproduce if we do not have the same sources and the same OS or the same projects, same etc ...: not easy :oops:

Re: Audio Crackle in standard mp4 render

PostPosted: Mon Oct 07, 2019 8:29 am
by ChipKng
Jim Simon wrote:
ChipKng wrote:Are you guys using the latest version of the nvidia driver?


I'm using Studio 431.70 without any audio issues.

I also don't use NVIDIA encoder for deliverables, as hardware encoding has a very long history of being inferior to software encoding.


If you don't use the HW encoding, you will not be able to reproduce the problem. It seems clear now, the problem is in the NVidia's driver and not with DR as other software suffers from it as well.
If you don't use that part by switching to software encoding, then it's irrelevant which version of nvidia driver you are using.

Re: Audio Crackle in standard mp4 render

PostPosted: Mon Oct 07, 2019 8:37 am
by kalpox
ChipKng wrote:
Jim Simon wrote:
ChipKng wrote:Are you guys using the latest version of the nvidia driver?


I'm using Studio 431.70 without any audio issues.

I also don't use NVIDIA encoder for deliverables, as hardware encoding has a very long history of being inferior to software encoding.


If you don't use the HW encoding, you will not be able to reproduce the problem. It seems clear now, the problem is in the NVidia's driver and not with DR as other software suffers from it as well.
If you don't use that part by switching to software encoding, then it's irrelevant which version of nvidia driver you are using.


Guys, stop blaming the wrong culprit. From the very moment you can do exactly the same with any other video editor with no issues (using PPro right now), the problem is in DR. Period. It's a critical bug and they have to fix it.

I have issues with newer and older Nvidia drivers, software and hardware encoding, h264, h265, MP4, MOV...