Topic: Mpv Drops Frames with Hardware Decoding Enabled

The MPC-HC + madVR combination with SVP can handle 60Mbps 4K video interpolated to glorious 144FPS no problem at all but sadly can't do tone mapping so I started using mpv instead. Mpv can top this by also doing tone mapping, but only with hwdec=no.

With any form of hardware decoding enabled (for example hwdec=nvdec-copy) mpv starts dropping frames by the dozen. What seems to be the problem?

I also asked about this on the mpv IRC channel but they couldn't help due to VapourSynth and SVP not being open source. A quote: "the shitty vs bridge is prbably what's killing the perf"

Hardware:
i7-7700K (4c/8t) @ 5,2GHz
RTX 2080 Ti
DDR4-3600

Re: Mpv Drops Frames with Hardware Decoding Enabled

VapourSynth IS open source wink

> With any form of hardware decoding enabled (for example hwdec=nvdec-copy) mpv starts dropping frames by the dozen. What seems to be the problem?

We'll never know why mpv is noticeably less efficient playing 4K+SVP than MPC-HC, but Blackfyre knows how to cook mpv+4k+4-cores CPU: https://www.svp-team.com/forum/viewtopic.php?id=4295

Re: Mpv Drops Frames with Hardware Decoding Enabled

I misread the part about VapourSynth. It's still external to mpv so they weren't too keen on diving in further.

But is this particular problem really about efficiency and why does it manifest using only hardware decoding? With software decoding mpv uses only 10% more CPU than MPC-HC while also doing tone mapping and it doesn't drop frames either. It's only when activating hardware decoding the drops start to happen on mpv.

Re: Mpv Drops Frames with Hardware Decoding Enabled

I really have no idea. However I do know that since recently many users experienced issues playing at 120+ fps in MPC-HC with NV cards, and one of the necessary step to fix it is switch from DXVA2 decoder to CUVID, otherwise for some odd reason it can't go above 100-110 fps. So it may be NV's drivers involved in all these problems. or not...

Re: Mpv Drops Frames with Hardware Decoding Enabled

Alright, thanks.

I'm just happy that 4K HDR can be watched tone mapped at 144FPS at all. It takes 300W of power to do, though. big_smile

Maybe one day we can get rid of ffdshow and replace it with something modern that has 10bit and HDR support. Mpv is not a very nice user experience due to lack of proper GUI.