VLC Stuttering Playback with UHD 4K on iMac Pro

macOS specific usage questions
bradstyle
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VLC Stuttering Playback with UHD 4K on iMac Pro

Postby bradstyle » 18 Jan 2018 00:25

Hello all,

I just replaced my early-2015 27" iMac with a 2017 iMac Pro. Up until now I had been experiencing smooth 4K playback under VLC 3.0 and 4.0 builds on the iMac. The iMac Pro appears to be playing about 10-15fps, there is evident stutter in playback.

2015 iMac – 4.0GHz i7 with 32GB of RAM, a 1TB flash drive, and a Radeon R9 M385X 4GB GPU, running the latest build of High Sierra
2017 iMac Pro - 3.2GHz Xeon W with 32GB of RAM, a 1TB flash drive, and a Radeon Pro Vega 56 8GB GPU, also running 10.13.2

I'm wondering if anyone knows what the cause is. Perhaps VLC doesn't support the GPU yet?

Thanks much :)

Lornadoo
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Re: VLC Stuttering Playback with UHD 4K on iMac Pro

Postby Lornadoo » 18 Jan 2018 23:22

I really don't know, but have you tried playing around in the advanced settings?

In Video, uncheck Drop Late Frames and Skip Frames. Any improvement?

Also, what video output module is selected? Do you notice a difference with "Mac OS X OpenGL video output" as opposed to "Core Animation OpenGL Layer (Mac OS X)"?

bradstyle
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Re: VLC Stuttering Playback with UHD 4K on iMac Pro

Postby bradstyle » 19 Jan 2018 23:34

After trying a bunch of things I switched it to Core Animation OpenGL Layer (Mac OS X) and it worked, but after quitting and restarting VLC it crashed everytime I tried to launch. Had to delete prefs and start from scratch. Now I can't reproduce the speedup.

To answer your question, unchecking Drop Late Frames and Skip Frames didn't yield any improvement on their own. I suspect some support for the new CPU and GPU need to be implemented somewhere, but I don't imagine this is a priority in VLC 3.0.0 and 4.0.0 development at present.

Any more possible advice greatly appreciated. Thanks.

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Re: VLC Stuttering Playback with UHD 4K on iMac Pro

Postby Lornadoo » 20 Jan 2018 10:47

I agree about the need for support of the new hardware. Since I am not using an iMac, I really can't say what is going on. I'm just using built in graphics on my punu Macbook. However, in VLC advanced preferences, Video-Output Modules-Mac OS X, you see at the top "Open GL/GLES hardware converter". Try switching this setting to Disable or to Apple OpenGL CVPX Converter and see what happens. I am just guessing, I have no idea what the outcome will be, but it might help improve.

Is there any setting on your iMac to disable your advanced GPU and just use basic CPU for video? I know that would not be ideal since it would be absurd to have to do so in order to get basic functionality, but it could be a temporary workaround.

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Re: VLC Stuttering Playback with UHD 4K on iMac Pro

Postby bradstyle » 20 Jan 2018 22:10

Thanks for the suggestions! Sadly no change in behavior, and no option (high level at least) to disable the GPU.

A few more observations: Audio plays perfectly while video appears to be playing at half speed, and showing far fewer frames than it should, hence the stuttering look. Obviously there is no AV sync. Having played around with it in many configurations now trying to get it to work I'm more convinced that VLC just lacks support for the new GPU. Patience is probably going to be my best policy here. Maybe I'll try some 2160p vids with crappy bit rates/small files sizes to see if those play any better, as I'm experiencing no difficulty with 1080p sources.

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Re: VLC Stuttering Playback with UHD 4K on iMac Pro

Postby bradstyle » 20 Jan 2018 22:37

FIGURED IT OUT!

What a relief. Preferences (Basic)>Video>Deinterlace>Off. That's the only change necessary. There are still long delays when jumping through the video clip (even on a flash drive capable of 3,000MB/s reads), but it plays and the audio is synced and life is 98% better than it was a minute ago. Thanks for the help.

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Re: VLC Stuttering Playback with UHD 4K on iMac Pro

Postby Lornadoo » 21 Jan 2018 00:11

Awesome! What a strange fix action! lol... Regardless, I am glad you figured it out. :D

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Re: VLC Stuttering Playback with UHD 4K on iMac Pro

Postby davec » 22 Jan 2018 19:58

Where does one get VLC versions 3+?

I've searched the videolan site and see only 2.2.x downloads available. Is source available for newer versions? Are you building this version yourself?

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Re: VLC Stuttering Playback with UHD 4K on iMac Pro

Postby Lornadoo » 22 Jan 2018 23:24

http://nightlies.videolan.org/build/macosx-intel/

click "last" for the latest nightly build (They are on 4.0.0 now)

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Re: VLC Stuttering Playback with UHD 4K on iMac Pro

Postby davec » 23 Jan 2018 01:00

http://nightlies.videolan.org/build/macosx-intel/

click "last" for the latest nightly build (They are on 4.0.0 now)
Thanks for that link.

If the current release is 2.2.x, and nightlies are 3.x and 4.x, why haven't they released something since 2.2.x?

I would think that whatever features were decided that launched development on 4.x, this would have been an opportune time to launch 3.

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Re: VLC Stuttering Playback with UHD 4K on iMac Pro

Postby bradstyle » 23 Jan 2018 01:38

In December they branched off to continue development on 4.0 while polishing 3.0 for release. From what I've heard VLC 3.0 should reach GM and be released soon. In the meantime just grab the last of the nightly builds of 3.0, it will serve you just fine.

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Re: VLC Stuttering Playback with UHD 4K on iMac Pro

Postby ePirat » 27 Jan 2018 06:29

Please try the official release candidates too, those are codesigned and include the (new) crashreporter:

VLC 3.0.0-rc7 for macOS can be found here https://get.videolan.org/testing/vlc-3. ... .0-rc7.dmg

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Re: VLC Stuttering Playback with UHD 4K on iMac Pro

Postby Nephele » 29 Jan 2018 10:37

According to VLC’s GPU decoding page, as the data is decoded in the GPU at the decoding stage and then transferred back to the player so that the other stages, filtering and streaming for instance, can be processed, this process can under circumstances be slower than without gpu acceleration enabled. What’s more, the VLC GPU decoding is only available for selected operating systems. While Windows Vista and newer versions of the Microsoft operating system are supported, Windows XP is not at this point in time. The majority of graphic cards should support hardware acceleration just fine. Make sure you have installed the latest drivers though.

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Re: VLC Stuttering Playback with UHD 4K on iMac Pro

Postby dfuhrmann » 30 Jan 2018 18:45

This report is for macOS, not for Windows.

But the tip to disable any video filters is important here all well. Some filters _are_ actually implemented in GPU, so it is wrong that data is copied back for them. But it can still slow down the whole decoding.

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Re: VLC Stuttering Playback with UHD 4K on iMac Pro

Postby thmtrxhsu » 23 Apr 2019 03:39

It is annoying to see lack of intelligence behind some of the VLC builds.
What does he mean.
Well, Macs have very specific hardware configurations, there is simply no reason for VLC not to perform its best from the the getgo yet it does not.
There should be no need for users to configure the options. I would say the VLC team could identify the cpu and gpu for every OS and apply a preset for all, but in fact there is no need to do so for OSX. Because I am a mighty power user, and I will provide the best options possible for VLC 3xxxx series balancing detail, color and providing maximum performance under the worst circumstances. These have been tested under Mohave with activity monitor.

I am using a 2009 mid Macbook Pro with Mohave (impossible as per Apple, but possible otherwise) and I changed the battery, put an SSD and now the memory is 8GB and it runs as good as when Snow Leapard was installed if not better so it has a 2.26 GHz Intel Core 2 Duo (a piece of --please stay polite--) and a NVIDIA GeForce 9400M 256 MB an even bigger piece of --please stay polite--. Two things should stand out from this from VLC's point of view, hardware acceleration isn't going to work and therefore the VLC performance will be dictated by CPU so any performance tweaks should be applied.

Mac OS X Mohave VLC 3xxxx series Tweaks (copy and use this as baseline for future builds):

In preferences, select Show All,

Audio should be set to SRC Resampler with Sync Function Fast.
Video, checkmark everything in between embedded video to mouse events
show video title for 0 milliseconds
show mouse cursor for 3000 milliseconds (to prevent mouse triggering performance degradation, that's why 3 seconds as opposed to 0)
uncheck display video snapshot preview
check video auto scaling and fix HDTV height
uncheck window decorations
deinterlace off
do not use any video filter as this takes a performance hit.
Subtitles / OSD uncheck everything
Output module, easy the only one that works with VLC 3.0 + Mohave is Mac OS X Open GL Video Output (drop down menu option)
Selecting the Mac OS X panel in output modules,
disable open gl hardware converter, set rendering intent to perceptual and tone mapping to hard clip out
Input / Codecs
scroll down, file caching 60 000 ms
Demuxers
Matroska: check preload mkv and preload clusters
FFmpeg (used for HEVC) check direct rendering, uncheck show corrupted frames, check hurry up, set skip frame to non-key, and skip IDCT to 4
allow speedtricks, skip the loop filter for non-ref, hardware decoding disabled
Access Modules: you should find Matroska and FFmpeg, just quickly verify that the settings are configured as previously indicated
FYI Stream output is for web streaming.
Now go back to simple view of options by clicking show basic and verify
Video that deinterlace is off
Subtitles, that enable OSD is off
Input Output Codecs that default caching is set to Higher latency (puts less stress on CPU), hardware decoding is off, post processing is set to 1,
skip the loop is set to non-ref and skip frames is enabled.

Done. VLC 3.0 will now give you maximum performance. Also there should be a link within VLC that goes to a page documentation supported GPUs for hardware acceleration, and the required drivers (propriety, linux).

If you want to give the best experience for mac users, above is the perfect baseline.
It is also what should be copied (where possible) for linux and windows unless there is incontrovertible reasoning to the contrary.
The problem with windows and linux is the former has a massive hardware pool and the latter the same in addition to a massive software pool.
In addition VLC has too many hardware acceleration options (its too complicated and needs to be agglomerated); basically there should only be one hardware acceleration option in simple view and one in the show all view, and second beside each of these there should be a link documenting under which circumstance hardware acceleration works (OS, Drivers, Hardware...).

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Re: VLC Stuttering Playback with UHD 4K on iMac Pro

Postby ehi » 07 Jul 2019 06:46

It is annoying to see lack of intelligence behind some of the VLC builds.
What does he mean.
Well, Macs have very specific hardware configurations, there is simply no reason for VLC not to perform its best from the the getgo yet it does not.
There should be no need for users to configure the options. I would say the VLC team could identify the cpu and gpu for every OS and apply a preset for all, but in fact there is no need to do so for OSX. Because I am a mighty power user, and I will provide the best options possible for VLC 3xxxx series balancing detail, color and providing maximum performance under the worst circumstances. These have been tested under Mohave with activity monitor.

I am using a 2009 mid Macbook Pro with Mohave (impossible as per Apple, but possible otherwise) and I changed the battery, put an SSD and now the memory is 8GB and it runs as good as when Snow Leapard was installed if not better so it has a 2.26 GHz Intel Core 2 Duo (a piece of --please stay polite--) and a NVIDIA GeForce 9400M 256 MB an even bigger piece of --please stay polite--. Two things should stand out from this from VLC's point of view, hardware acceleration isn't going to work and therefore the VLC performance will be dictated by CPU so any performance tweaks should be applied.

Mac OS X Mohave VLC 3xxxx series Tweaks (copy and use this as baseline for future builds):

In preferences, select Show All,

Audio should be set to SRC Resampler with Sync Function Fast.
Video, checkmark everything in between embedded video to mouse events
show video title for 0 milliseconds
show mouse cursor for 3000 milliseconds (to prevent mouse triggering performance degradation, that's why 3 seconds as opposed to 0)
uncheck display video snapshot preview
check video auto scaling and fix HDTV height
uncheck window decorations
deinterlace off
do not use any video filter as this takes a performance hit.
Subtitles / OSD uncheck everything
Output module, easy the only one that works with VLC 3.0 + Mohave is Mac OS X Open GL Video Output (drop down menu option)
Selecting the Mac OS X panel in output modules,
disable open gl hardware converter, set rendering intent to perceptual and tone mapping to hard clip out
Input / Codecs
scroll down, file caching 60 000 ms
Demuxers
Matroska: check preload mkv and preload clusters
FFmpeg (used for HEVC) check direct rendering, uncheck show corrupted frames, check hurry up, set skip frame to non-key, and skip IDCT to 4
allow speedtricks, skip the loop filter for non-ref, hardware decoding disabled
Access Modules: you should find Matroska and FFmpeg, just quickly verify that the settings are configured as previously indicated
FYI Stream output is for web streaming.
Now go back to simple view of options by clicking show basic and verify
Video that deinterlace is off
Subtitles, that enable OSD is off
Input Output Codecs that default caching is set to Higher latency (puts less stress on CPU), hardware decoding is off, post processing is set to 1,
skip the loop is set to non-ref and skip frames is enabled.

Done. VLC 3.0 will now give you maximum performance. Also there should be a link within VLC that goes to a page documentation supported GPUs for hardware acceleration, and the required drivers (propriety, linux).

If you want to give the best experience for mac users, above is the perfect baseline.
It is also what should be copied (where possible) for linux and windows unless there is incontrovertible reasoning to the contrary.
The problem with windows and linux is the former has a massive hardware pool and the latter the same in addition to a massive software pool.
In addition VLC has too many hardware acceleration options (its too complicated and needs to be agglomerated); basically there should only be one hardware acceleration option in simple view and one in the show all view, and second beside each of these there should be a link documenting under which circumstance hardware acceleration works (OS, Drivers, Hardware...).
Had carried out this out, attempted on a MBP early 2015 retina and suddenly the file would not play. Has anyone else had this problem once applied these settings?

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Re: VLC Stuttering Playback with UHD 4K on iMac Pro

Postby digibud » 30 Dec 2019 18:45

I also carefully set my VLC to the specs listed and resulting playback was horrible and unusable.


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