I've found what may be a bug that can lead to horrendously long renders. If it really is a bug, it has probably affected almost everyone reading this post.
I'm rendering my annual two-camera Nutcracker shoot, and couldn't figure out why the render slowed down after the first three minutes of the project. I found the answer, and think it is a Vegas bug. I need someone to test my results. I've only tested on V10, but I suspect this problem exists in later versions. Here is a link to a 50 MB zip file that contains the V10 VEG, plus two small video files:
Render Bug Test
Here's a brief description of what causes the problem. I have HDV on the top track and HD (1920x1080) interlaced on the bottom track. In my two camera shoot, I cut between them, but don't bother to remove the HD when it is covered by the HDV. Someone bumped my HD camera, and it is slightly out of line, so I uses pan/crop to rotate it. Thus, in this screenshot, the top track contains HDV video, and the bottom track contains HD video, slightly rotated:
When the render gets to the HD portions (where there is a gap in the video in the top track), it slows down. This is what I would expect.
When the project renders the HDV on the top track, it goes just as slow as the HD. But, if I remove the "unused" HD event from that is under the HDV, guess what? The render of that portion of the project speeds up, and speeds up by a LOT.
Thus, Vegas appears to be using the video on the bottom track, even though it is obscured. This seems like a bug, and a major one at that. This has happened before. Many, many years ago, in Vegas 5, I saw a similar behavior when Vegas would slow down the whole project when any compositing was done anywhere on the timeline, even if it was only done for a few frames.
Compositing causes ENTIRE project to render?
Testing the bug will take less time than it takes to download the file. To do the test, unzip the files to a folder, open the VEG project file and render it to NTSC DVD Architect Widescreen MPEG-2. Write down the time it takes to render. Then, delete the event from the second track and repeat the render.
I just did this test (I was doing a large render in the background, so the absolute times are long) and with the HD event on the bottom track, the render took 22 seconds. Once I removed it, the render took 6 seconds. Almost 4:1 !!!
If this is a bug, it is not minor.