c_major:
I don't know how to make a determination about keyframes. As I understand it, broadcast TV uses I-frames (keyframes?) quite a bit so that TV receivers can quickly lock (or re-lock) onto signals. The broadcast TV recorder that I am using claims to record the exact MPEG-2 stream as it comes over the air. The signal is strong without problems.
However, I did an experiment and discovered something troubling about VideoPad for my application. I loaded the file for the 3-hour TV broadcast (2.5 hours). Next, I immediately put it in the Sequence Bin (no editing whatever). After that, I burned a Blu-ray disc (3+ hours of coding, plus more for time for burning and verifying). Here is what I found:
The recorded program on the Blu-ray disc is visibly degraded from the original video file (which I can play on my laptop). The major degradation is that motion is no longer smooth, as if there are skipped frames, or a frame rate conversion. It also appears that the video has lost some detail. For what it is worth, the recorded program occupies about 75% of the space on the disc.
My speculation: VideoPad cannot handle a large file directly, so it does lossy compression to make the file smaller (thus the long load time, with the laptop's processor being heavily load and generating a lot of heat all during loading). I could live with this, annoying though it is. But then it appears that editing is done on this compressed file, and this edited, compressed file is then the output put on Blu-ray disc. I would have hoped that the compressed file would be used only as a proxy to define the edits, which then would be applied to the original file.
I also did another experiment where I loaded three one-hour files, also from broadcast TV. It took less than 5 minutes to load the 3 hours of video. Once again I did no edits. I simply put them into the sequence bin, one following the other to make a three-hour sequence. I then immediately burned a Blu-ray disc. As with the single 3-hour video, encoding proceeded at appoximately real-time speed. When this disc was ready, I compared it to the original video files. There were subtile differences, mostly loss of smoothness of motion.
I am bothered by the large amount time it takes for encoding for Blu-ray disc. I should think it would proceed fairly quickly, since the source file is MPEG-2, and the resulting file for the disc is also MPEG-2. No doubt there is some "repackaging" that needs to be done, but the data should not need to be modified.
Given what I see, it seems that VideoPad always re-encodes, even if the input and output are the same format (MPEG-2 in this case). It looks like the re-encoding process is lossy. This is greatest disappoint for me. I was hoping for a lossless process. I guess I need to restart my search for video editing software.