Refresh interval during play, and setting precise scales

I want to use screen capturing software to make a movie of the Audacity display while it’s playing, and I’d like to make sure that the cursor moves smoothly in the movie.

I think I need to know what the refresh interval is for the display, so I can make sure it doesn’t clash with the capture frame rate.

I’ll also need to set the horizontal scale precisely, in order to make sure that the cursor is moving the same number of pixels with every refresh. The only way I can think of to do that is to select a precise length of audio and Zoom To Selection. Is there any other way? It would be nice if I could set it in pixels per second.

For maximum smoothness, assuming that your computer and screen capture program are capable of doing it, set the capture rate to the same as the screen refresh rate.

My initial problem is not that the capturing is being messed up by incompatible frame rates, but that the moving cursor isn’t smooth even when played live.

I’ve got about a minute of audio displayed on screen, and when I play it, the cursor moves along in a “jittery” fashion. I don’t know if this is because the computer isn’t keeping up with moving the cursor along, or if it’s the result of rounding of the cursor position to an in integer.

By looking at a screen dump in Gimp, it looks like my horizontal scale is about 23 pixels per second.If Audacity is trying to redraw the cursor every, say, 1/100s then it needs to move it by 0.23 pixels, so it’s going to have to round it off, and will keep it still for a few redraws, then move it, then keep it still, etc, in order to make the average speed work out to 0.23px/s. By my calculations it should keep it still for 3 redraws, move by 1 pixel, keep it still for 3, move by 1, still for 4, move by 1, then repeat. This is assuming that’s how often it redraws.

The end result is a jittery cursor, which might not matter to most users, but means I can’t capture a smoothly moving cursor.

So I need to know the redrawing rate so I can adjust my horizontal scale till it results in a more even movement pattern.

Just for the record, this old thread seems to be discussing this same issue of cursor smoothness:

That discussion went on for several months with no resolution.

I’ve used Camstudio to capture the screen while playing, and it appears that the refresh rate is 0.3s. I’ve used Zoom To Selection to set a horizontal scale that should result in the cursor moving close to 1 pixel per refresh, and although it’s stopped being as erratic, it’s still what I’d called jittery. I’m coming to the same conclusion as the OP in that thread - it’s just not refreshing often enough to be smooth.