Audio delay/echo issue

Hi Graeme,

Thanks for getting back on this.

It actually makes sense this being some sort of bug in QT.

When I play back the ProRes (HQ) 24 bit/48kHz raw files in QT I also encounter the echo/delay issue. But in MPEG Streamclip they sound just fine. Also in VLC. And in FCP X too.

The smallest sample I can send you is 1.68 GB. I'd be happy to assist you. Send me the FTP info and I'll upload.

In the meantime I've tried a work around, manually converting one of the raw files from 24 bit to 16-bit in Compressor, and re-linking to that new file from FCP X. It seems to work and sync is intact. Exporting XML -> X2Pro -> AAF now suddenly sounds fine in Logic.

So tonight I'm throwing all the files in Compressor, convert overnight, and hopefully re-link tomorrow.

/Mads

Hi Mads,

X2Pro uses the QTKit framework to extract the audio. It asks QTKit what the bit depth and sample rate are for a clip, then requests audio with the exact same characteristics. Usually, it then gets back the raw samples from QTKit. Unfortunately, in this situation, it appears that QTKit is performing some conversion.

We think this is a bug in QTKit and we have reported it to Apple, but unfortunately we still don't have a working solution. They made one suggestion which made the audio "sound" better, but it actually seemed to re-sample to a slower rate. We have reported this back to Apple but still haven't got a response.

We are still chasing this with Apple, but at this point I'm afraid that we don't have a solution.

It might help if we could have another sample file, preferably something quite small (our only other sample was 1.5GB). Do you have anything smaller, and if so would you be able to let us take a look at a file that exhibits this issue when X2Pro has converted it? I can provide FTP details if you can.

Hi Graeme,

I'm editing a show for Danish Broadcast Corporation (DR Ultra) and I seem to be having the EXACT same problem.

We also recorded Apple ProRes 422 (HQ) files, with two mono channels of 24-bit PCM audio at 48kHz. When the AAF is imported into ProTools those audio files sounds slightly out of sync. ONLY those files. The rest of my audio is fine.

The problem seems to lie in the bit-rate conversion.

In the X2Pro Preference menu the 'Convert non-PCM audio' says:

"Whenever non-PCM audio is encountered for it must be converted to PCM audio data for embedding into the AAF files."

But my audio IS PCM, it's 24-bit PCM 48kHz so X2Pro shouldn't do any converting, right? But it does.

I've attached a screenshot for the QT inspector of one of the raw media files.





Best regards,
Mads Larsen Nielsen

Yes, you may pass this file on to Apple. I trust that it will not be made available to the general public, as it contains proprietary information.

We already figured out a workaround using Xto7 for Final Cut Pro to export an OMF that successfully imported into my PT system.

Please keep me updated on your findings. Thanks for all your help!

X2Pro is using the QTKit framework (from Apple) to extract the audio from your mov file, and we think that your file may have exposed a bug in QTKit.

We would like to talk to apple about this, can we have permission to pass the mov file on to them in order to demonstrate the issue?

You may be able to work around this issue by replacing the audio for all the clips in your project that exhibit this behaviour with an exported version that does not, although that may not be practical if there are a large number of clips like this. Would you like me to look into working out how you could do this, or are there too many of these clips in your project?

Thank you!

I am looking into the original files on my end as well.

We shot this on the Sony F3 camera.
We recorded to AJA KiPro Quad
We recorded Apple PRoRes 422 (HQ) files, with two mono channels of 24-bit PCM audio at 48kHz. There was no transcoding or re-wrapping of the files.

I can hear what you mean, and that is very odd indeed.

I have asked the developers to have a look. I'll keep you updated with what they find.

In the meantime, any information about that clip would be useful, for example:

• What camera it came from
• Whether the camera was recording into mov files, or whether the clip was re-wrapped
• Whether the camera was recording using ProRes and 2xMono PCM audio, or whether the clip was transcoded

I'm uploading that file now.

I did listen to that file and it has the same issue. We brought it into FCP again and it played back just fine. These files were not converted, merely transferred off the original recording hard drive. I am going to see if I can access the original files that were recorded.

Are you able to also upload "LM_13.mov" from the "Final Cut Events/LearningMasters_Concur/Original Media/" folder on the disk called "edit6array"?

No problem. Thanks for looking into it.

Sorry, I didn't see your private message telling me that you had provided the files. I have downloaded them and am starting to look into it now.

I'll keep you updated...

Just checking in to see if you have been able to figure anything out on your end. It'd be great to know if it's something we're doing somewhere along the chain so we can adjust and avoid the issue in the future.

Thanks!

Excellent. I have sent you a private message with connection details for our FTP server so that you can upload the files.

Yes, I can send you project files later this morning.

Thanks for your response!

That does sound very strange.

Would you be able to create a simple project, using just one clip and see if this creates an AAF with the same issue?

If it does, would you then be able to upload the project and event file so that we can take a look here? If you can do this, I can provide FTP details in a private message.