4 ms·

The reason you don't see any tearing is probably because video players under X have gotten better about "guessing" when the frame is supposed to be displayed. T

by md8z 5y ago

The reason you don't see any tearing is probably because video players under X have gotten better about "guessing" when the frame is supposed to be displayed. The knowledge to do that has accumulated over the last 30 years and it's a pile of hacks, and it's still possible for them to tear under various circumstances because X is still fundamentally an unsychronized protocol (unless you use a compositor with frame sync).

kaba0 5y ago
It’s more like the video card: doing vsyncing, especially on video.
- md8z 5y ago
  I don't understand, a video card cannot "do vsync" like that. If the program sends its contents at the wrong time then the video card can't do anything about that, the correct information is simply not there.
loxias 5y ago
Thanks for this! I was thinking similarly, but you phrased it better than I could. My observation was "it used to suck, just like wireless, and suspend/resume, but now it doesn't." which matches perfectly with "software has built up a pile of hacks... aka bug fixes". BTW, despite any appearances to the contrary, I recognize (and look forward to!) the superiority of an architecture based on fixed rate interrupts rather than a freewheel unsynchronized protocol. I was just afraid, previously, that: 1) All my stuff is gonna break! (Consider I've been using the same setup unchanged since the mid 2000s, and it's got a lot of self written code) 2) I'm gonna be stuck with a system I consider ugly! 3) My stuff breaking will be in exchange for nothing I consider worthwhile in return! Now that I read the great article https://www.phoronix.com/scan.php?page=article&item=x_wayland_situation&num=1 https://www.phoronix.com/scan.php?page=article&item=x_waylan..., much of my FUD has melted away. I know that #2 and #3 aren't true, #1 is probably true but now I'm looking forward to it.
destructionator 5y ago
> X is still fundamentally an unsychronized protocol Again, factually false. X has various synchronization options from the older double buffer protocol to the XSync extension to the GLX/DRI vsync commands. I've also never seen tearing in X since like 2006.
- md8z 5y ago
  No, it's not factually false, those fall in the "pile of hacks" I mentioned, and none of them work in all cases, some of them are highly dependent on driver support which is spotty. I can show you various bug reports from the last few years of people still complaining about tearing. This problem is not even remotely close to being solved in X and I don't think it ever will be. Again just look at the bug reports. Meanwhile, if you plumb atomic page flipping through the whole system and make it mandatory, the chances of having tearing are pretty nonexistent. But you have to drop legacy stuff from X if you want to do that.

by md8z 5y ago

kaba0 5y ago

It’s more like the video card: doing vsyncing, especially on video.

md8z 5y ago
I don't understand, a video card cannot "do vsync" like that. If the program sends its contents at the wrong time then the video card can't do anything about that, the correct information is simply not there.

loxias 5y ago

Thanks for this! I was thinking similarly, but you phrased it better than I could. My observation was "it used to suck, just like wireless, and suspend/resume, but now it doesn't." which matches perfectly with "software has built up a pile of hacks... aka bug fixes". BTW, despite any appearances to the contrary, I recognize (and look forward to!) the superiority of an architecture based on fixed rate interrupts rather than a freewheel unsynchronized protocol. I was just afraid, previously, that: 1) All my stuff is gonna break! (Consider I've been using the same setup unchanged since the mid 2000s, and it's got a lot of self written code) 2) I'm gonna be stuck with a system I consider ugly! 3) My stuff breaking will be in exchange for nothing I consider worthwhile in return! Now that I read the great article https://www.phoronix.com/scan.php?page=article&item=x_wayland_situation&num=1 https://www.phoronix.com/scan.php?page=article&item=x_waylan..., much of my FUD has melted away. I know that #2 and #3 aren't true, #1 is probably true but now I'm looking forward to it.

destructionator 5y ago

> X is still fundamentally an unsychronized protocol Again, factually false. X has various synchronization options from the older double buffer protocol to the XSync extension to the GLX/DRI vsync commands. I've also never seen tearing in X since like 2006.

md8z 5y ago
No, it's not factually false, those fall in the "pile of hacks" I mentioned, and none of them work in all cases, some of them are highly dependent on driver support which is spotty. I can show you various bug reports from the last few years of people still complaining about tearing. This problem is not even remotely close to being solved in X and I don't think it ever will be. Again just look at the bug reports. Meanwhile, if you plumb atomic page flipping through the whole system and make it mandatory, the chances of having tearing are pretty nonexistent. But you have to drop legacy stuff from X if you want to do that.