Thank you for taking the time to reply. You are right that the device explorer could only read an AVCHD file which I just created with the DVX200. It does not see the large MP4 files I created during a music performance the night before. And as far as vegas is concerned, the DVX200 does not exist if there are no AVCHD files When I first got the HMC40 camera and just got the data files from the memory card, if a 4 Gbyte boundary was hit, there would be a gap or silent spot when I spliced the two files together. To solve that problem I started importing clips via device explorer and it would stitch everything together for me. I was instructed by support to do so (either sony vegas at the time or panasonic). I could set the camera recording for a couple of hours, play the concert, and then process the video/audio. I am in the build of a more powerful computer to deal with the 4k video files as the files are now 10x as large. The DVX200 camera in AVC mode does nothing but 1080 video and down (just checked the recording options when I did the test). In MOV or MP4 mode, it does 4k video. So now the question is, when I am ready to process the big files, will they stitch together ok, and I am hoping the answer is yes. I was using the old procedure because that's what I have always used. I have processed 4k mp4 files before, but I just haven't thrown any big ones at my computer yet, and those files were short clips - maybe 5-10 minutes - that I could just download and not hit a boundary. Thanks again for your insight. It would certainly be nice if vegas could use device explorer for other formats. If you have any other insights along these lines I would be most grateful to hear them. The DVX200 guide by Barry Green goes into stitching issues with MP4/MOV files and some software has no problem with Mp4/MOv formats as far as gaps go, and some software does. I think it was vegas 11 that had the aforementioned gaps unless imported via device explorer.

I would be surprised if the 4K files have also a 4GB limit; they don't on my Sony cameras. Difference is actually more in the way the SD card is formatted and you should use SDXC cards, exFAT32 for 4K recording and there should be only one file per clip. That is how all my Sony cameras work. The files can be huge, 10-20GB for longer recordings and I just use the File Explorer to import it. Panasonic is always going it's one way so no guarantee there.

The 4k files are 40 Gbytes, not 4 Gbytes with the DVX200. I was referring to the old HMC40 1080 camera which produces AVC files and was providing some background on how the HMC40 and Vegas worked. I am a creature of habit for things I don't really care about, so once I found a download solution that worked, well, I stick with it so I can get on to the video production. I should have mentioned that I am using twin U3 128 Gbyte sandisk SDXC cards in the DVX200. Nothing else would let me record long segments in 4K video mode and the DVX200 lets you do a number of things such as use each card for a different format at the same time - such as 1080 on one and 4K on another, or as I have it set up now, in relay mode so if one fills it will go to the next card. In ye olden daze the Sony cameras used those memory sticks so I never went with them. Sony has always made very good products especially in the pro line. And I did a lot of research before going the Panasonic way with camcorders. With still cameras I am a nikon man. And that goes back to film cameras. If I put the DVX200 into avc mode then its more like the HMC40. And I still use the HMC40 which is pretty beat up, but being a solid state camera, just keeps going. That was a big selling point to move on to the DVX200 which answered all the design issues of the HMC40 and went quite a bit further. It certainly cut down on the learning curve of the DVX, but there is still plenty to learn. I also have some kodak zi8s which I use for off angle camera stuff and then mix all the video together when I want a multi camera set up. The quality of the 1080 video on zi8 for the price I paid for them always impressed me. And you could even put a rhode SVM on the Kodak and get surprisingly good audio/video.

So now the question is, when I am ready to process the big files, will they stitch together ok, and I am hoping the answer is yes. I was using the old procedure because that's what I have always used.

I am really confused now especially by this sentence above. Why would you need to stich 4K files? The should not be split at all.

because the session is 3 hours long.

because the session is 3 hours long.

Are you now talking about replay recording? That would be different story. Many cameras to have a small gap when it comes to relay recording, no way around as far as I know.

Well, when you use device manager with importing avc file, vegas would stitch the files together as noted above. Now that we have moved on to mp4/mov files they are supposed to not have a gap which depends more on software so we'll see what the luck of the draw is there. There is a big discussion on how to deal with this from years back when 4k first started, and some video editing software realizes what is going on. As noted in this link, the data is there, its how the software deals with it. Panasonic support told me years ago that the avchd file standard contained links to keep the breaks out and it always has. I won't know what happens until I process the big files, and even then, there are solutions mentioned on this thread that may solve the problem if it exists in vegas 15: https://www.vegascreativesoftware.info/us/forum/how-to-combine-mp4-files-split-by-the-camera--100894/