Waveform drawing (reading rather) from movies is incredibly slow. This would cause problems.
It may be possible to detect if there are movie files in queue and move them to the end, so fast files would be processed first.

Hello, here because I was thinking of doing this and just did a quick search to see if anyone else had the same idea as me. In four years of Blender VSE use I've never worked with a track with an audio clip where turning the waveform on wasn't the first thing I did. I'm sure the read issue with long tracks is still an issue that might get in the way of this, but raw video in the VSE is at usually most ten minutes long for me and I suspect a good amount of others using the VSE as well. Actually, I had a two hour long track lying around that I was going to clip that I've just tested and the waveform took ~6 seconds to render, which is a pretty fine tradeoff for me in return for having the checkbox on by default, or even just removed. If long read is still an issue we want to deal with, I can try take a crack at it to get this PR pushed through.

In D7914#360509, @David Yang (davidy22) wrote:

Hello, here because I was thinking of doing this and just did a quick search to see if anyone else had the same idea as me. In four years of Blender VSE use I've never worked with a track with an audio clip where turning the waveform on wasn't the first thing I did. I'm sure the read issue with long tracks is still an issue that might get in the way of this, but raw video in the VSE is at usually most ten minutes long for me and I suspect a good amount of others using the VSE as well. Actually, I had a two hour long track lying around that I was going to clip that I've just tested and the waveform took ~6 seconds to render, which is a pretty fine tradeoff for me in return for having the checkbox on by default, or even just removed. If long read is still an issue we want to deal with, I can try take a crack at it to get this PR pushed through.

I think, that now waveform processing is faster than it was before, but this is with new machine too so hard to judge. I still experience cases where there are bottlenecks, like adding video directly from SD card, just to review it does take minutes to draw waveform on 10min file. You can't really predict or detect such bottlenecks.

Feedback in general for this feature is to make processing multithreaded, which would make it more unlikely that whole system would be halted by one bottleneck. currently progressbar is not working, but with multithreaded system it would be nicer to draw just available portion of waveform.

Making this system multithreaded would be relatively simple I think if you want to have a go at this, you can contact me on VSE chat https://blender.chat/channel/vse where we can discuss details (same handle - iss). I can point you to resources and help with things.