@Wovian  ... do you have Sony Vegas Pro 13 or earlier (at least back to 10)? If yes, those versions have Dolby AC3 Pro as an audio render option, AC3 Pro provides a lot of accessible render settings (i.e. the template is not greyed out). And there is a choice of 2 workarounds to get AC3 Pro working in Vegas Pro 14, 15 and 16 (though I can't get either workaround to work in 17 or 18). Have a look at item 31 in:

https://www.vegascreativesoftware.info/us/forum/vegas-pro-faqs-and-troubleshooting-guides--104787/

The link in item 31 will take you to another forum post which provides workaround details.

A workaround requirement is that DVDA is installed which you obviously do have installed already.

Also, in DVDA, double-check File/Properties/Disc Properties to make sure that the audio settings match or better the audio properties of your AC3 Studio render from VP14.

Thanks @Dexcon

I do have VP13 still installed and have tried the workaround but on rendering the audio I still only have AC Studio as an option and not Pro. I restarted the PC to make sure. Is there anything I have missed?

Actually I may have jumped the gun - apologies I do now have Surround DVD as an option but its under the AC3 Studio header so I did not see it until I expanded it, if that makes sense?

I think this has worked but I do not get an option to customise the surround sound template in VP14 (But it was as you know in VP13) so the volume is still a little on the soft side but not too bad.

In later editions of VP what do you do to burn a Blu Ray in 5.1 surround sound? I was just about to upgrade to VP 18 as I have many editions of this software but wouldn't do so if I there was no rendering in surround sound? Seems like a step backwards?

Are you comparing the DVDA audio Preview? Don't do that; it is only downsampled stereo, not Dolby processed, and is nothing like what will be on your DVD.

@Wovian  ... it should appear as in VP13 as Dolby Digital AC-3 Pro in the Render As selection. Here is the basic workaround I used successfully years ago for VP14 to 16:

In VP14's folder FileIO Plug-Ins, rename ac3studioplug.dll to any other name that you desire [e.g. just add an X], then copy the ac3plug folder from VC13 to VP14 in the FileIO Plug-Ins folder, rename it to ac3studioplug, open the folder and rename ac3plug.dll to ac3studioplug.dll. The render option in Render As should then appear as Dolby Digital AC-3 Pro. There should be no Studio listing.

DVDA will not preview the audio correctly when using 5.1. As Musicvid said, it can only downmix and even then, one of the channels will have more sound than the other. Trust that what you hear ion Vegas is what you will get on your DVD or software designed to play a DVD and 5.1 audio.

As per @Musicvid and @Former user there will be a difference as they've outlined. But my experience is that the quality is not lower, rather the volume is a way lot lower when previewing the audio track in DVDA.

Yes. In addition to the Dolby transforms not being expressed in the DVDA audio preview, encodes made with AC3 Pro will preview with much lower volume in one channel, a reflection of the 90° phase shift introduced by the PLII matrix.

AC-3 Studio uses a lower loudness standard by default, which cannot be altered, so the final disc volume will be significantly lower if it is set in VP for Audo CD levels (0.0 dBFS peaks) or for streaming (typically -14 LUFS). AC-3 Pro has loudness options, so the VP audio preview and final disc (AC-3) loudness can be about the same.

Thank you @musicvid, @Dexcon, @Former user and @rraud.

I was just listening to the timeline, not in Preview mode.

I have managed, by following @Dexcon's steps to see just AC-3 Pro in the render as option. Rendering of the audio took 20 mins this time instead of the usual 5 and I got the error message at the end of the render so I guess something different is happening! Sounds so much better too and when I burn the Blu ray the audio is not recompressed like it has been for the last few years.

You folks have helped me out so many times over the years.

One final question - what is the story regarding VP18? Does this fix still apply?

@Wovian

 ... regarding VP18? Does this fix still apply?

I have been unable to get either workaround to work in VP17 or VP18 on 2 different computers. I'm guessing that access to the workarounds has been blocked in 17 and 18. It still works in VP16 so when I'm ready to render audio in 17 or 18, I'll copy the audio tracks over to VP16 and render in AC3 Pro there. That's the plan at this time anyway. If there's a plugin problem (e.g. VP16 not recognising a plugin from 17/18), then I'll have to render that/those audio event/s in 17/18 first so that only a clean .wav event is used in 16. Most plugins are 3rd party like iZotope which should [cross fingers] work in VP16.

What a pain. I think that kills my planned update to VP18 then.

@Wovian

An alternative solution is to use a ffmpeg command line to convert the audio rendered in Vegas to the AC3-Pro format.

DVD Architect will accept this audio and will not need to make a new rendering at the time of the final render, as the audio will already be in the correct format.

This workaround has always worked correctly for me and I have never had any problems. See the video below showing the process.

I'm sending to you the ffmpeg with the command line that I use for you to test. You can download it from this link bellow:

https://www.dropbox.com/s/uiv12nfd8s85jns/ffmpeg%20v4.0%20with%20AC3-Pro%20Command%20Lines.rar?dl=0

Here is the original advice I posted back in 2008 for using AC3 Pro without introducing unwanted audio levels changes in your DVD output:

https://www.vegascreativesoftware.info/us/forum/ac3-encoder-is-putting-agc-on-my-sound-track--100986/#ca619708