[DJ_Izumi]

Firstly, if XBMC already has multithreaded 4K h.264 support, I apologize but would appreciate some help in understanding what the issue is instead.

Anyway, deets first:

Test Video File:
http://videos5.hd-trailers.net/videos/El...K-HDTN.mp4

System:
AMD A8-3870K
16GB RAM
Windows 7 Ultimate
XBMC 13 Gotham Alpha 4

My experience seems to be that 4K h.264 decoding in XBMC is not multithreaded. When I attempt to playback the 4K file, playback begins using software decoding (Weather 'Allow DXVA' is enabled or not) and it promptly gets choppy at about 10fps, the CPU usage floats around 25%-27% and it's basically unwatchable. This is much like watching certain 10bit h.264 media on machines with lowerish multicore CPUs before Gotham alphas allowed multithreading.

I do have success playing 10bit h.264 and even 1080p h.264 lossless which demands upwards to 70% of the CPU at times. (Student film maker, so I have some h.264 lossless files of my own work laying around which I use to upload to YouTube to avoid doing two lossy compression passes) However 4K seems to bury the needle on one core and in the case of the A8-3870K one core just ISN'T enough.

As we're on the verge of 4K it seems not allowing multithreading on 4K is a major shortcoming in the near future even if it isn't quite one now.

[davilla]

4K is NOT near future, maybe a year of so away. The size impact alone makes net transport prohibitive. HDTV makers just got done suckering people into 3D and you expect everyone to buy 4k replacements now ?

[DJ_Izumi]

4K is NOT near future, maybe a year of so away.

If 'a year or so' is not 'the near future' when do you think 'the near future' is?

[davilla]

next week, next month.

[Ned Scott]

I don't understand all the technical details, but I know that Hi10P multithreading was enabled because there wouldn't be some issue where it could be hardware decoded, because no hardware video decoders for Hi10P exist, making it safer or something.

However, 4k does have hardware decoders on the market now, so I assume the same logic can't be applied there until some larger issues with multithreading are dealt with.

I think. Something like that...

[jpsdr]

Only 10bit is multithreaded. If your 4k video is 8bit, it's not.
Just by curiosity, test this.
You have to disable dxva to enable multithreading, but after, you should have multithreading on your 4k video.

[wsnipex]

at least on linux nvidia and intel can hardware decode 4k fine. AMD's driver(dunno about the hardware) is limited to~2k

[DJ_Izumi]

Only 10bit is multithreaded. If your 4k video is 8bit, it's not.
Just by curiosity, test this.
You have to disable dxva to enable multithreading, but after, you should have multithreading on your 4k video.

This makes it playable if DXVA2 is disabled. With DXVA2 enabled, it still uses software decoding but only a single thread, just as you prescribed.

I'm a bit confused however, with this compile and even the Gotham Alpha's, with DXVA2 enabled it still doesn't use ff-mpeg-dxva when I try to playback h.264 4K, where as for 2K or 1080 it does use DXVA, but it only does it single threaded. Meanwhile, with DXVA2 enabled, playing back 10bit 1080p or Lossless 1080, it goes multithreaded. ...Why was this sort of multithreading added but it doesn't use multithreading for 8bit? It clearly knows that it must use the software decoder after all so why have the software decoder multithreaded in some scenarios but not the others?

[Lunatixz]

I agree that 4k is another year or two out of becoming a mainstream option... Most streaming services can bearly stream true 1080p and blu-ray 4k is not in full production and won't be until TV support for it is added...

[giaur]

Why not hardware acceleration? Nvidia supports 4k on Windows by Pure Video HD and Vdpau on Linux (drivers 319 and above). Have no idea about AMD but I'm pretty sure 4k on Windows is supported (and probably not supported on Linux).

But I agree that 4k is not any priority - there is no 4k videos and no 4k displays today, 1080p is enough.

[davilla]

Personally, rather than waste time thinking about 4k support, I'd prefer that we devs work on refactoring AE and getting the existing video playback much better. There is a lot of work to be done in these areas.

[DGMurdockIII]

but at least basic 4k support would be at start then you could worry about other stuff later and so you don't fall behind when there is aloth of content that start coming

[Ned Scott]

We already support it...