avoid_negative_ts - why change default recommendation? has implementation changed?

[bryc]

Making this a Q&A discussion as it is probably not a bug.
I've just tried the latest LC and noticed that I now get a warning when attempting to merge segments of a x264/aac mp4.

LC recommends make_non_negative.

But here's the kicker - the old version I use, actually gives a warning if make_non_negative is used. I've always used make_zero, which is the default for the older version. I never needed to change it; it's never given me an issue (as far as I know?).

So, this causes some confusion.

Has there been an implementation change? is make_zero safer on older versions that later became unsafe on newer versions?

Or are the behaviours the same between versions, and this is just purely a guidance change?

Personally, I've noticed that using make_non_negative can have inconsistent behavior between video players. For example If you cut 3-5 frames ahead of a key frame, This option appears to allow ffplay (and Chromium) to skip past those first 3-5 frames somehow, but VLC (and Firefox) does not. I thought it'd be useful as an alternative to "smart cut", but it's a problem if it doesn't work in VLC/Firefox. make_zero on the other hand, has consistent behavior between most players, when I cut 3 frames ahead, it always snaps to the previous keyframe.

So I'd rather keep using make_zero if the warning is benign.

[mifi]

It’s purely a recommendation change. It was made here: dca83a8
Here’s the reasoning behind the change: #1874 (comment)