I've already installed two more codec packs with AC-3 which don't work

@GoToVegas Of interest which packs were they?

Might be simpler to transcode the source files until the fix is in. Plenty of free utils out there that will automatically give say aac as audio.

For anyone still dealing with this problem, I found a quick easy solution. There is a product called "Prism Video Converter" by a company called NCH Software (you will find them easily). I think they have a freeware version, but I'm not sure. I bought the one-time purchase option for $34.99. They are a reputable company, and the software is safe to install.

It works well, and you can easily convert any video files that have the AC3 encoded audio into any format you choose. It processes fast, and you can load multiple files in the queue to batch process.
I had a couple dozen old home videos in MPEG-2 that I reconverted with Prizm. Now they work fine in Vegas and Premiere (and probably everything else).

@Gregory-Hastings 

Try the beta build out. We have a new AC3 decoder which hopefully fix this problem.

Although I have already solve the AC3 problem with a 3rd party software, I'll give the beta a try just to see if it fixes another problem I'm having.
I'm trying to do some screen captures, and am getting the video captured just fine. But it's not capturing the audio. And I do have the speakers audio source selected, and the audio is showing up on the bar graphs, but isn't getting recorded into the mp4 file.

Thanks

The current video capture utility is not actively being worked on. A promising replacement capture application is being developed, and if successful, would replace Vegas Capture. Even if this application works well, we are quite a long ways from being able to release it.

Thank you very much VEGASDerek. I've now installed the 22.0 (Build243).

I have now tried a few files from old Sony camcorders with AC5.1 and also Sony DSC V1 with AC2.0. All audio tracks now working correctly again. The only thing missing is sometimes the visual representation of the waveform within the audio track with AC5.1. With AC2.0 the waveforms are always shown correctly. But that doesn't bother me at the moment. Thank you very much for the good and correct solution from Vegas!

@VEGASDerek - I assume that my VP19 will not helped by anything in the VP22 beta. I also have MAGIX Movie Studio 23 Platinum which does open the m2ts, etc. files that crash VP19, so is it possible to point VP19 to the codec/s used in MMS23P? I know you'll ask why I can't use that s/w instead of VP and the answer is that it is primitive compared to VP. I need to have stereo audio waveforms visible and I want to work in the s/w environment I have supported for several versions over many years. Also, no, I can't recode everything I work on as there is a lot and it takes so much time I just don't have. I'd u/d past VP19, but I have stayed across all the problems and I just don't want to buy more trouble. Magix support is pretty good, but this AC3 trouble stinks.

I also have MAGIX Movie Studio 23 Platinum which does open the m2ts, etc.

That's strange. As you are aware this AC3 problem results from a Windows change with Win11 24H2. This affects all software that was using the Windows provided AC3 codec which is no longer available in fresh installs of 24H2. So I wonder what MMS 23 is using or by chance do you have MMS23 and VP installed on different machines?

@EricLNZ - Same PC, an ASUS TUF Gaming A15 with 32MB, AMD Ryzen 5800H, nVidia GeForce RTX3060, SSD drives for speed, and Win11 Pro 24H2. I also have tried other s/w such as Corel's VS2023 which works as does Shotcut and even little old SoundForge AudioStudio 12 which is primarily an audio editor but does playback m2ts, etc. files in sync without any issues except slow rendering after editing the contained AC3 audio. But I need to use my VP19 because I have lots of bits I can re-use. Pulling the AC3 carpet out from under chosen products is not right by any test and reduces the capabilities of the Vegas product I bought because of it's "Swiss Army Knife" reputation and the best professional GUI, in my opinion.

@jaydear Yes I agree "pulling the AC3 carpet out' was a bad move by Microsoft but no doubt they had a reason.

SoundForge AS12 being old is possibly using a licenced Dolby AC3 codec but what are the others using? Do you have any codec packs installed?

In case I have problems in the future I've bookmarked this https://www.techspot.com/downloads/6457-microsoft-dolby-ac3-installer.html. I've not tried it so cannot comment on its suitability. If you search the net you will find several suggested solutions plus there's the AnWave solution mentioned earlier in this thread.

@EricLNZ - VP19 is an old version too and afaict has the ac3 codec sitting in C:\Program Files\VEGAS\VEGAS Pro 19.0\FileIO Plug-Ins\ac3studioplug and the aac codec in ~\FileIO Plug-Ins\mcaacplug. VP19 crashes if I even look like I'm going to open a file with material using one or the other. I don't have any codec packs installed because I'm afraid that other things in my system will be corrupted or hacked, etc. I tried downloading the file from techspot, but it gives an error.

It'd be nice to hear from Magix here about all this codec difficulty and have them offer up some actual solutions to allow us to continue using the features we paid them good money for. Are we actually using MS codecs in VP, or is it supposed to be using the ones included in FileIO Plug-Ins? Too much is hidden away.

I'm having the same problem with VP 22 Build 250. The sound starts OK then switches off, back on, back off, then finally stays off. What's the fix? I've restarted, closed the program then reopened, etc. I recorded a video with my IPhone 16 and had this problem before build 250 but a restart solved the problem. None of that works now. I see a link from EricLNZ above so will try that. If not, hope someone has a solution. Thanks.

The video and sound work fine on other apps so this looks like a Magix VP problem.

@jaydear As far as I'm aware VP19 uses the Windows AC3 codec. As for "ac3studioplug" I assume its not the actual codec but a "plug" that links VP19 to the codec. But I'm just guessing. I'm not a pc expert. As for files with AAC audio they should not be affected by the Win11 24H2 problem so it perhaps indicates something else on your system. Suggest you lodge a Support ticket.

@charles-mcguyer Your problem appears unrelated to this m2ts/ac3 problem thread. I doubt that your iPhone is using AC3 audio in a m2ts file, but I'm always open to correction if wrong.

Best you start your own thread.

@EricLNZ - I have now successfully d/l'd the 7z file from Techspot (my download manager wasn't managing at all!) and I can report that AC3 audio does not crash VP19 now and plays back as it should, so that is a win. Thanks very much for the link. That also confirms that VP19 and probably other versions, use the AC3 codec in Windows (if it's present 🙃). The AAC audio difficulty is yet to be probed.