I'm another one of those people who uses SONAR and Vegas. SONAR will never do what Vegas can do, and Vegas will never do what SONAR can do. So, I don't expect to export a video from SONAR. I import the video from Vegas, create the score to it in SONAR, then export only the audio and import it into Vegas, where there are all the export options I would ever need.
 
It would be convenient if SONAR paid more attention to video, and I'm confident Microsoft will nail down the loose ends on their Media Foundation platform eventually. However, the option to attract more pro video people is relatively limited because they're locked into Pro Tools for film and to some extent with TV, Digital Performer. The market for video with more relaxed specs (e.g.. YouTube videos) is growing and SONAR addresses those needs perhaps not elegantly, but sufficiently for now...with the expectation that there will be improvements in Windows. Meanwhile, at least for my needs the Vegas/SONAR combination is tough to beat.

Anderton
I import the video from Vegas, create the score to it in SONAR, then export only the audio and import it into Vegas, where there are all the export options I would ever need.
 

Craig, yes, that is exactly what I do as well!
However, the music you create in Sonar will be slightly out of sync when you bring it back in to Vegas (or any other program) to marry it back to the video file. (If the video file is an MP4 or QT file) It's hard to tell unless you do certain tests as it's only out by a frame or so. As you know, even if it were only off by a "sample" you would get phasing/flanging problems if any duplicate audio were playing simultaneously.  
 
My test: I will open an MP4 in sonar, export a bit of the dialogue out as a broadcast wave. Then import it into vegas against the same video file to check it. It will be out of sync with the original dialogue.
 
Currently, I have to slide my score audio in Sonar (70 ticks earlier) before creating a broadcast wave if I want it to sync up. (It will still be out by half a tick, but I can't get a smaller slide resolution in Sonar) *This amount differs between different versions of Sonar (X1,X2,X3,Plat) just slightly.
 
The sync difference is consistent throughout the session as if there is a small amount of "padding" before the mp4 starts in Sonar. Even audio that is at the very beginning of the file will have the same offset as audio from the end of the file.
Again, this does not happen when using uncompressed video files such as AVI. I have found issues with WMV as well.
Bottom line is: everyone uses MP4, QT etc. these days and normally comes from the Mac world.
Thanks     
 

Very helpful, thanks! I've never noticed the issue because in my world, nothing is being combined with a video's existing audio track...all audio (narration or music) is being generated in SONAR and added to the video, or looped to replace audio (thank you VocalSync).
 
However, your last post piqued my interest so I "asked the internet" and found multiple threads about padding and desync issues with MP4s and some conversion options. I'm going to try your test and see if there's any way to mitigate the issue.
 
Just out of curiosity did this happen with the old MS video engine? Come to think of it...did it even support MP4?

Okay...it just got weirder. Try this test, and let me know what you find.
 
1. Create a project in Vegas (I used Vegas 12).
2. Render it as an MP4; leave the project open.
3. Bring the MP4 into that project.
4. Compare the start time of the audio in the rendered video compared to where the audio starts in the project itself. 
 
When I did this, they did not line up; the audio in the MP4 was later. So even when using Vegas to render a file, then bringing that file directly back into Vegas, there was a timing issue with the audio.
 
If I rendered only the audio in Vegas as WAV or FLAC, then brought it back into Vegas and compared it to the audio in the project, they lined up perfectly. If I rendered only the audio as MP3, then brought it back into Vegas and compared to the audio in the project, it was late (later than the MP4 audio). When I brought the MP4 into SONAR, rendered only the audio, and compared it to the original audio in the project is was also late (somewhat more than the MP3).
 
So it seems any rendering to a lossy format, no matter how minimal, affects timing whereas rendering into a lossless format does not. This only partially explains why bringing in SONAR's audio is later than the MP3, but I suspect that if there's an issue that occurs while encoding (e.g., as happened with the MP3) there more be even more of an issue if encoding and decoding (e.g., as happened with SONAR's audio). This may explain dannyjmusic's comment about SONAR liking AVIs better; apparently Vegas likes uncompressed formats better too, and would also explain the various threads about desync issues with compressed formats like MP4.
 
One more tidbit: It seems the offset occurs when importing into SONAR, not exporting. So in addition to the time added at the beginning of the audio due to exporting from Vegas, there's additional time added due to importing into SONAR. This tends to support my suspicion that issues happen during both encoding and decoding. If I render the audio from the MP4 imported into SONAR then bring it back in to SONAR, it lines up perfectly with the imported MP4 audio.
 
 
 
 

I think I first noticed the sync issue in 2015 sometime, but as you say, H.26X codecs haven't opened in Sonar until sometime in 2014 I think. I used Sorenson 3 QuickTimes or Mjpeg in the past and never had sync issues. Perhaps I did have the issue though and just didn't notice. When Sonar started playing MP4s I think I was just so glad that I didn't have to convert the video files to get them to open in Sonar any longer that I didn't think to check. 
 
My guess is it probably has been like this ever since Sonar started working with MP4 but nobody ever noticed. I think I only discovered this by accident because I had brought some dialogue back into Vegas from Sonar and noticed the sync was out. Perhaps since newer versions of Windows came along (8 and so on) I'm still on Win 8. I'm gonna test on my son's machine as he's on Window 10. Not sure when the MS vid engine changed, was it Win 8?
 
Anyhow, if you also have any sync issue after testing please post! My work around at this point is to just do the test I mention above, but slide the audio back a little each time to see exactly how much it's off; (70 ticks in my case), then apply that slide before exporting any final BCW cues. I'll look into some of the conversion options you mention above.
Cheers  
    

I'm using Windows 10...but even if the import issue in SONAR is fixed, that won't fix the export problem in Vegas that adds silence to the beginning of the rendered audio.

Yes, the export/import in and out of Sonar, always syncs back to the mp4. The problem only occurs when bringing the audio into a different program like vegas.
 
I did your test just now and yes, they were out of sync, just enough to flange. But I think any compressed format export has the potential to change a little, I would forgive that. My score cue exports are always wave files so they are uncompressed, they should match the same video file in vegas.
 
And still, if I test this in ProTools 10, all is fine back and fourth from vegas. Sonar's video container is somehow not displaying the video at the correct start time or something. There is no drift issue. If it's all good and consistent between protools and vegas I doubt it has to do with the video being rendered at a lossy format and more Sonar's ability to work with them properly.  
 
Also, as I mentioned before, the MP4s I'm using have visual time code burn in, and it displays the same thing as Sonar's clock! Yet if I have a beep at 01:05:00:00 in sonar, the visual timecode says the same thing as the sonar counter but if I bring that beep into vegas and line it up to the same VISUAL code, it doesn't sync to picture the same way!!! I find that the weirdest of all!
 
Sorry if this post is a little scattered... 
 
 
 

I have no trouble running MP4s in Sonar Platinum. It will as long as one has the right codec to run it. If you install K-Lite mega codec pack Sonar will run any video format that K-Lite supports.
 
 

Thanks John, the issue isn't playing the files. I have k Lite and Shark etc...  the issue pertains to sync after exporting audio from sonar and then re syncing again to the same vid file in other programs

I should also note that if I have an MP4 with a burned-in visual time code on it, and it's first frame visually indicates a time code of, let's say 01:00:00:00, when imported to Sonar, the first frame of video I see has a visual time code of 01:00:00:01. So I can see why any exported audio will be late when synced back up to the original mp4 in vegas. 
 
What is Sonar doing with that first frame from the MP4? (and it's not the length of a frame it's a frame and 3 ticks...)
In Vegas and Protools, the first frame I see on the visual code is 01:00:00:00 as it should be.