vd-lavc-dr is very slow.

[tsjnachos117]

I've noticed that my CPU usage with newer (custom) builds of mpv has been really slow lately. With some decoders, the computer is almost unusable. I narrowed the problem down to the default vd-lavc-dr. Setting this option to "no" brings my CPU back down to something usable. I wonder why this is? I have multiple computers, but only one specific laptop (Dell Latitude e6410) seems to be affected.

PS: Is there a way to disable this system-wide? I know I can change /etc/mpv/mpv.conf, but that doesn't seem to affect Celluloid (which uses libmpv). Perhaps there's some configuration switch I can use when compiling?

OS: Linux Mint 20. CPU: Interl Core i5 M 520 @ 2.40GHz

[tsjnachos117]

OK, I've just found a good (albiet temporary) workaround: I made a shell script in the source directory called "set_vd_dr". Here are it's contents:

\#\!/bin/sh

exec sed -i '/^ \{8\}\.dr = 1,$/ s/1/0' mpv/video/decode/vd_lavc.c

This will set the.dr = 1, declariation in mpv/video/decode/vd_lavc.c to 0. I guess it's a boolean operator? I have verified that mpv still builds, and runs OK. Compiling with --enable-libmpv-shared in mpv_options, I got a library version that seems to make Celluloid disable the vd-lavc-dr option by default as well.

Of course, this is just a workaround until a real solution is found, but it will still due just fine for now.

[Dudemanguy]

I think you just want to set --vd-lavc-dr=no. It's an option.

[sfan5]

Low end Intel iGPUs are known to have severe performance issues with DR (though maybe yours is just too old in general?). I have considered adding a blacklist of GPU models so DR would automatically be turned off but that's a bit suboptimal.

[tsjnachos117]

@Dudemanguy There's no easy way to do this system-wide with libmpv. I share this computer with a couple of people, and talking all of them through the process of adding a command-line option in Celluloid's options is a pain in the butt. Hacking the build as I have seems easier.

(For regular mpv, adding the aforementioned line to /etc/mpv/mpv.conf works just fine.)

[Dudemanguy]

It's up to the libmpv API user (or Celluloid in this case) to expose easy ways for users to configure things. Not an mpv in any case however, so I'll close this.

[tsjnachos117]

Oops! I only just realized I posted this in the mpv-build repo. This was meant to be in the mpv-player repo. My bad. Anyway, my main point was "this option makes mpv slow", not "help me hack this plz". I guess it being closed was for the best, especially given the workarounds already discussed.