It seems the problem occurs with anamorphic video, like 720x576 4:3 PAL DV in this case. The closest output preset is 768x576. That does produce full-frame 4:3 video, but also causes scaling of otherwise unmodified frames (and makes the output unsuitable for authoring to DVD later in the workflow). Trying to avoid that I set a custom output resolution of 720x576 and that's when horizontal letterboxing occurs.
I can't wait! What would really make my day would be Avisynth input too.
That would already help a lot. The simplest approach (and which I find easiest to work with by far) is to simply navigate the timeline by frames. Dragging the pointer, or clicking the buttons or clicking the timeline or controlling playback simply scrolls forward or backward so many frames, then naturally stops on a frame boundary. I can't actually think of a single use case where a user would need to position the pointer within a frame? In terms of on-screen values, display the current position in both frame count and time value, and accept input in both forms. That would be perfection in my world! Something else that might also improve from navigating by frames - I see 50fps clips are navigated in 0.04s increments, instead of 0.02s.
All test clips I exported without modifications on my part came out 1 frame shorter than the source. The test clips were all Type 2 AVI of varying length, some DV and some Lagarith. This happened regardless of input or whether output was to DV or to Lagarith. In fact, from Rightclick -> Properties on clips in Video Files it seems they are short by 1 frame after input already. I have a handy 2-frame test clip for you if only I could upload it.
Of the ones I've come across, VirtualDub and AvsPmod are two of the best examples of exposing and configuring controls for keyboard shortcuts.
How do I send the Excel spreadsheet to you?
If there's anything else I can contribute or help with, let me know. Your product already scored very highly, and the fact that you are receptive to suggestions well, gives me hope .