VC1 in mkv Playback Choppy

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gertrude Offline
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Joined: Jun 2014
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Post: #1
Hi,
I am experiencing playback problems with VC1 mkv's using XBMC.
I have tried same source files in powerdvd and they work fine.
Problem is same whether or not I enable hardware acceleration.
Tried on both a windows machine running gotham, NVidia gtx570 and Ubuntu machine, gigabyte brix.
h264 is fine.
This is not a settings issue. It is not a video driver issue. It is not a source video issue.
The problem appears to be with XBMC. I have tried latest nightly build (7th June 2014), problem still present.
Can anyone shed some light on this issue please?
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mrhyde1969 Offline
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Post: #2
What file is giving you Problems? Is it Interlaced?
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gertrude Offline
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Joined: Jun 2014
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Post: #3
The file is a BLURAY backup using bytecopy lossless mkv backup.
Not sure if it's interlaced. How do I tell?
I have tried modifying all settings to do with interlacing...software, hardware etc...to no avail.
I have a number of these backups that all play fine with powerdvd.
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_Shorty Offline
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Post: #4
I just dumped my Blade Runner - The Final Cut Blu-ray to an mkv file and its playback is very slow/choppy in the latest stable build. I'll get a debug log to post here in a little while.

edit - This is just a dump with MakeMKV, and not a re-encode.
(This post was last modified: 2015-01-11 05:55 by _Shorty.)
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_Shorty Offline
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Post: #5
http://pastebin.com/X9WYWYuq

I'm seeing roughly 25% CPU0 being used, and roughly 75% CPU1 being used during playback and I'm only getting between 18-19 fps out of it. That seems to me like it might be doing software decoding. I haven't looked at the log yet to see if it is. But there's the debug log I got just now when playing back somewhere between the 5:00 and 6:00 marks of the movie.
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_Shorty Offline
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Post: #6
I really had the itch to watch Blade Runner so I tried VLC tonight, which was playable for 90% of the movie. It did show stuttering and dropped frames here and there for a handful of seconds, but for most of the movie things were ok. That said, VLC also used a ton of CPU. In my case, I did a bit more research on my video card (old NVidia 8600!) and found out that it only supports partial decoding of VC-1 content, with a good portion of decoding still being done on the CPU. And that is exactly what the problem is in my case. Originally I had thought that NVidia's mention of VC-1 decoding meant it decoded everything, and so I should be seeing negligible CPU usage, as I do for H.264 content, but that's not the case at all. After doing some more digging and finding out that only portions of decoding are done on this GPU it all made sense. *sigh* and doh! I guess for now I'll be transcoding my Blade Runner Blu-Ray with Handbrake, until I upgrade that machine down the road.
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