MPC-HC Subtitle Default Settings Update

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MPC-HC Subtitle Default Settings Update

Post by ocyl on Thu Jan 03, 2013 6:32 am

The following are a series of feedback and suggestions for the maintainer(s) of K-Lite Code Pack (KCP) in regard to the values set, and the options offered, by the KCP installer. The area of focus here is subtitle rendering.

As of v1.6.5.6366, the MPC-HC team has changed the default value of the "Sub Pictures to Buffer" setting in Options -> Subtitles from 3 to 10. The change may have been made in accordance to recent changes in GPU drivers. For instance, starting in nVidia graphics drivers v301.42 and all the way to the latest v310.70, the default value of the "Maximum Pre-rendered Frames" setting in nVidia Control Panel -> 3D Settings -> Manage 3D Settings is now "Application-controlled" instead of the traditional value of 3. I have done some testing on this personally and can confirm that subtitle rendering performance is indeed improved when both settings are left at the new default values. "Allow animation when buffering" is checked by default in MPC-HC v1.6.5.6366.

I have also tested different values for "Sub Pictures to Buffer" and found that the maximum value of 60 significantly reduces the frequency of "flashing" effect that I used to experience, and complex subtitles are loaded much faster between scene changes. However, the usual concerns with longer buffers are CPU utilisation and seek time. During my testing, difference in CPU utilisation was about 2%, which might be statistically insignificant, but I did notice longer seek times. The impact of seek time delays may be more pronounced on video cards with slower memory or on integrated GPUs.

During KCP v9.6.5 installation, the default setting for internal subtitle renderer is to allow animated effects without buffering. This is not necessarily a good practice anymore because the current MPC-HC behaviour drops entire video frames, and not just subtitles, when it's trying to catch up. On slower computers, the end result is that viewers will see the player jumping across scenes (e.g. from 0:10 to 0:15 to 0:20, instead of showing 0:10 ~ 0:20 without subtitles). Given that most people would likely prefer less fancy subtitles to skipping, an arguably better choice for older computers is to turn off subtitle animation altogether (but still keep some buffers in the pipeline). I have tested this and can verify that turning off animation is most effective when one's main objective is to get rid of the flashing effect.

Since we are on the topic of subtitle rendering, I should add that the "3D Surfaces" setting in MPC-HC Options -> Playback -> Output appears to offer better error/overlapping concealment when large canvases are used by typesetters. The performance difference is minimal (not noticeable) when antialiasing and anisotropic filtering settings in GPU drivers are left at default (application-controlled), but the visual difference is vast where this becomes relevant. Basically, what happens is that the horizontal tearing lines that sometimes show up due to subtitle rendering and flushing (note: not vsync) are much well hidden, and sometimes entirely eliminated, by 3D surfaces. 3D surfaces is a recommended setting in MPC-HC v1.6.5.6366, whereas 2D surfaces is the default.

Putting all pieces together, below are the internal subtitle renderer setting selections that I would like to suggest KCP to offer during installation.

  • Static Subtitles: animation off, 10 sub pictures to buffer, 2D surfaces;
  • Allow Animated Effects (with Buffering): animation on, 10 sub pictures to buffer, 3D surfaces (<--- default);
  • Allow Animated Effects (with Maximum Buffers): animation on; 60 sub pictures to buffer, 3D surfaces.

The middle selection is suggested as the new default because I think that it represents a good compromise for the wide ranges of equipment that are out there. The other two selections are for people with much slower and much faster computers.

Including repeated testing, this has taken me over 10 hours to put together. I hope that the KCP team will consider these feedback and suggestions.


Last edited by ocyl on Mon Jan 07, 2013 2:55 pm; edited 5 times in total

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Re: MPC-HC Subtitle Default Settings Update

Post by Admin on Fri Jan 04, 2013 12:46 am

The subpicture buffer is completely unrelated to any frame buffering done in your driver.

If you have problems with tearing and flickering, you should consider upgrading to Windows 7. That has much less problems than XP.

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Re: MPC-HC Subtitle Default Settings Update

Post by ocyl on Sun Jan 06, 2013 4:58 am

Admin wrote:The subpicture buffer is completely unrelated to any frame buffering done in your driver.
I see.

Will the setting's default value be increased in future versions of KCP?

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Re: MPC-HC Subtitle Default Settings Update

Post by Admin on Sun Jan 06, 2013 6:56 am

Maybe. But not insanely high values like 60. The optimal settings depend on many factors. What works better on your system may actually work worse on other systems.

Can you give some details about your CPU and amount of RAM?

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Re: MPC-HC Subtitle Default Settings Update

Post by ocyl on Sun Jan 06, 2013 10:58 am

I upgraded my computer about two weeks ago, but had also tested this prior to the upgrade.

Old Computer: AMD Athlon 64 X2 4800+, 4GB DDR-400 2-3-2-5
New Computer: Intel Core i5-3570K, 4GB DDR3L-1600 8-8-8-24

Only values 3 and 10 were tested on my old computer, but moving to 10 brought rather obvious improvement without any noticeable drawback. I ran a 3-pass test with values 10, 20, 30, 40, 50, and 60 today, and found that even though 10 could play most things okay, 20~30 appeared to be the optimal range for more intense ASS subs on my new computer.

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Re: MPC-HC Subtitle Default Settings Update

Post by Admin on Sun Jan 06, 2013 11:31 am

How much memory does MPC-HC use with a buffer of 10 and 60 on your new computer, with rendering resolution set to desktop?

Do you have any recommendations for videos that I can download that have really heavy subs?

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Re: MPC-HC Subtitle Default Settings Update

Post by ocyl on Sun Jan 06, 2013 4:27 pm

With both 10 and 60, memory usage increases by about 300 MB on my new computer. I tested each buffer value several times, and each time the computer was restarted and sat idling for at least five minutes before a file was opened. I had already set rendering resolution to desktop in MPC-HC.

One of the videos that I frequently find myself going back to for testing subtitle rendering performance is the opening theme (0:41 ~ 2:11) of uploaded.net g5dpk1y0/from/fz58qj. Trying to play it forward and backward reveals that 15~25 seems to be the buffering sweet spot on my new computer.

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Re: MPC-HC Subtitle Default Settings Update

Post by ocyl on Mon Jan 07, 2013 5:35 am

ocyl wrote:15~25 seems to be the buffering sweet spot on my new computer.
I am going to revise this down to 10~20. 25 and above tend to take too long for buffer to flush; 5 and below flush too often.

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Re: MPC-HC Subtitle Default Settings Update

Post by ocyl on Mon Jan 07, 2013 2:35 pm

After hours of additional testing, it's becoming clear to me that 15 has the best balance, so it's what I will use from now on. I imagine that it's likely a good buffering value for other people who have bought a Nehalem, Westmere, Sandy Bridge, or Ivy Bridge based CPU in the last few years, as well.

I am adequately comfortable with 15 now that I am beginning to wonder if two internal subtitle renderer setting selections in KCP installer (instead of three) will be sufficient moving forward:

  • Static Subtitles: animation off, 10 sub pictures to buffer, 2D surfaces;
  • Allow Animated Effects: animation on, 15 sub pictures to buffer, 3D surfaces.

3D surfaces have an additional benefit of allowing MPC-HC's "Display Stats" function (Ctrl + J, or View -> Renderer Settings -> Display Stats) to work. Of course, any change to KCP is up to the package maintainer.

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Re: MPC-HC Subtitle Default Settings Update

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