No Decoder for AC3 audio on Windows 10 1803

I started a project recently using AVCHD video with AC3 embedded audio. I was in running Windows 10 1709 x64. I initially started the project with Resolve 14.3, but switched to, and restarted with, Resolve 15 Beta 2. Audio worked fine with both versions.

Having started the project, I upgraded to Windows 10 1803 once it was released. Upon re-opening my project I had no audio: the audio tracks were completely blank, and the debug logs filled with a message of "unable to find audio codec"

I tried clean installing Resolve 15 Beta 2 onto my upgraded Windows 1803, and clean installing Windows 10 1803 then installing Resolve 15 Beta 2 onto the clean installation. I also tried Resolve 14.3 on again, and got the same results: perfect audio on 1709 and no AC3 audio with 1803.

This feels like something has been removed from Windows 10 1803 by Microsoft, but if so what? Anything I can install?

I can't provide any logs at the moment as I am back on (the working) 1709 in order to finish the project. It'll be done by Wednesday though, so I can re-install Windows 10 1803 and provide some debug logs then if I can't find a solution in the mean-time.

Thanks all for any ideas or insight!

Project finished! So I have now done a fresh install of Windows 10 1803, installed updates and drivers and installed Resolve 15 Beta 2, and the same problem is still there: namely no AC3 audio.

I've done a log dump which I have uploaded to Onedrive; you can find it here:

https://1drv.ms/u/s!ArW22DtXQmnajHmpIG1YsOaCWObp

You can see lots of "Failed to decode clip <D:\Temp\001.MTS>, track: 0, position: 744960 - Cannot find the codec for decoding. MFT Process output returned error: -1072861856" messages as I scrubbed across the clip in the error log. I couldn't see any reason this was occurring in the logs though.

Dear Linda,
I don't know if your problem is solved, but I have exactly the same problem after the Windows 10 April 2018 update. As well with Resolve 14 as with Resolve 15 Beta3.

In the log file it gives errors for all the clips: Cannot find the codec for decoding.

The strange thing is that audio of the videos don't not play in the timeline viewer, but when I open a video file in the source viewer it plays well. Therefore, I don't think it is a missing AC3 codec in Windows. However, when I go back to the previous Windows version (1709) everything functions well.

I'm having the same issue on Beta 4 on 1803.

I'm gonna send feedback to Microsoft to see if they have anything to do with this.

I thought I read somewhere on the Microsoft site that the latest Dolby Digital codec removed the ability to decode audio from PES streams (mts, m2ts, ts files). I could be wrong, though.

Try rewrapping to mov. If that doesn’t work, we may have to add transcoding ac3 audio to PCM in our workflow.

Dear Gary,
Your right; when I transcode my .mts files into .mov files the audio works. Thanks for the tip.
However, I thinks it is a bit cumbersome when you need to transcode all your video footage before you can start to build your project in DVResolve.
I read on webfora that users of Magix have the same problem. Access to the codec is via Windows without the licensing hooha and that this has changed in Windows 10 1803.
So, it should be nice when Blackmagic should take care about the access to the codec.

Uulke, I don’t think we can count on BMD providing this back into the free version of Resolve since this was a Microsoft change and the free version of Resolve uses the Microsoft codecs for these files. When you purchase the Studio version of Resolve, codecs for those files are provided in the installation package.

AC3 Audio is the codec mostly used in consumer AVCHD files. So I think BM should implement this codec in the free version and "Resolve" this major issue. Unfortunately the AC3 sound problem has always existed in the free version of Davinci.

Maybe I am stupid, but what I don't understand is that Resolve plays the AVCHD files well in the source viewer (only not in the time line viewer). You can also transcode the files in Resolve using the media management. Is the codec not needed in these cases?

Also the free VLC media player has no problems after the update to Windows 10 1803. How difficult can it be for BM to solve this?

[Peter Chamberlain]

We are looking into what Windows changed and how to work around that.

Peter, Thanks for giving me confidence that my setup is OK.
I have been using Resolve for a month or so with excellent results until today.
Loaded a current project to find the audio did not work, waveform looked good.
Imported an MP3 music file. All good.
After investigation without result decided to import a video shot. The Audio track showed no waveform. Audio of shot played in VLC.
Decided to visit forums to get info. Found that Adobe Premiere Elements seems to be having trouble too.
Found this thread which seems to be on the right track. My Win 10 is 1803.
Shall wait for more info on this thread, thank you Peter.

Great, the problem is solved with the release of beta 5 last Thursday. All audio works; thanks.

I have the same problem, upgrading W10 made the audio stop working. Unfortunately this didn't change with the last beta or the actual Resolve 15 version.

AC3 decoding costs money and BM is not providing it natively (specially with free version), instead using Win10 capability to decode it. 1803 update most likely made some change which broke decoding in Resolve.

It's always going to be now a chase for any changes which MS does. This is the price of using OS capabilities instead of providing native support.

Is this an "official" Blackmagic response? I understand this, though I thought that normally decoders are free, only encoders cost. That's why VLC and others play ac3 perfectly well (I thought).

Still, I wonder what happened here:

Great, the problem is solved with the release of beta 5 last Thursday. All audio works; thanks.

?

As far asI know decoding AC-3 requires/ed license which costs money (although I think actual Dolby patents have now expired: https://www.cnx-software.com/2017/02/10 ... ary-1-2017).

I don't work for BM, so far from an official statement