2 capture of same source, not in sync?

[Chris Solo]

Here's something that has me bumping my head against the wall. I captured a movie tonight for a project and just in case there were any dropped frames, I grabbed it twice at 1080p60 and twice at 720p60. It's from a Roku box, hence the 60fps. And sometimes 720p will appear sharper than 1080p from some sources that stream hence the decision to cap both resolutions. I was on a time limit so I wanted to try and cover all of my bases. Well I loaded the two 1080p caps up on timelines in Vegas, turned opacity to 50% on video track one so I could see both video files. I found a good frame to sync with and got them perfect. Then when I hit play, sync is fine for several seconds then they drift. I did the same with the two 720p caps and everything was good. I am leaning heavily toward my system not being able to cap 1080p reliably.

Capture source in this case was a Roku 2
Capture device is an Elgato Game Capture HD60 Pro
Capture software is the Elgato software (but I am reading up on OBS, dxtory and Virtualdub)
System is Windows 7 Professional 64-bit, Intel i7 CPU, 8 cores, 12 gigs of ram and a partridge in a pair tree.

Any ideas here? While the system or the Elgato hardware/software could be culprits, it could also be the Roku 2 maybe? During capture, the game capture software is the only thing open although I realize that other processes are running. I did kill any that I knew I could but didn't kill things I was unsure of. Thanks in advance for any insight.

[zoidberg]

Did you import the transport streams themselves into Vegas? It could be that Vegas' internal decoder is not frame accurate for seeking (Premiere has this problem).

[Chris Solo]

I did not. I tried but could not get the .ts files to open. I'm thinking maybe for things I capture that need to be synced with other sources, I could use virtualdub to convert to lagarith? I had not even considered that the software's "conversion" into an mp4 may be flawed. Makes sense. Thanks!

[jerryshadoe]

I've been working with Vegas for many years and it is notoriously (based on my experience) unreliable when it comes to keeping frame accuracy of LOSSY video streams. To get around this, I trasncode anything I'm working on to LAGS first. Yes, it adds an extra step to your workflow and takes a lot of space, but this is the only way I can use Vegas

[Chris Solo]

That's fine with me Jerry. As long as it's a known issue I won't sweat it. I can do a conversion and it's better to do that anyway. This was kind of a down and dirty check of things to see if the caps were good. Thanks for the heads up on Vegas and lossy formats. Good info.

[jerryshadoe]

Yeah, I learned the hard way, while editing a custom cut of a tv show into film-format, that using lossy sources in Vegas is not a good idea. I had AVC encoded and XviD encoded video, chopped up into about 1400 segments and during rendering I noticed that some of the shots would contain a frame from the previous/next shot/scene and when trying to "correct" the errors, that would just create more errors during rendering. (repeating/missing/blank/incorrect frames) I ended up having to recut the entire thing from lossless elements from scratch. Grrrrrr!!! That was a f***load of work...

It also happened to me a few years back, when working with all h264 (baseline) and MPEG2 lossy video too, where if I would loose frame accuracy after chopping the video streams up to align them with each other...

I finally got to the point (about two years or so ago) of switching to editing using lossless files exclusively.

[Chris Solo]

Glad you learned the hard way so I won't have to Thanks again.

[jerryshadoe]

No prob... happy to help