.mp4 playback too fast? (1 Viewer)

[technoweary]

The TV runs at 50FPS on menu's, Live TV etc. and changes to 24FPS when I play the Videos when using Nvidia Renderer.
VideoLAN confirms that the frame rate is changed to 24FPS when playing in Windows.
If I use MPAR the video playback frame rate is 25FPS, and this gives the unwanted speed up.
Whether MPAR is not controlling the Nvidia display card or the TV I cannot guess, but as I said the Nvidia Audio renderer appears to correct the problem.

 

[davidf]

MP is not setting the video refresh rate to 24Hz as configuration is set to 23hz (in Dynamic Refresh Rate). As you monitor doesn't support 23.976 it cannot change to it, which is why I've suggested changing the setting to 24Hz (or 48Hz). VLC is telling you the number of frames per second in the video file (fps) not the refresh rate your monitor is running at (Hz) - your monitor is running at 50Hz and if you watch carefully you'll notice that both MP and VLC will be displaying the a frame twice every second to make up for the fact that the fps of the file and the frequency of your monitor do not match.

However, if you are happy to sacrifice the video quality then leave the settings as you have them.

 

[technoweary]

I am confused?
Video from the PC is 50fps to the Pioneer TV and when videos are playing it changes to 25fps using MP Audio Renderer and 24fps using the Nvidia Renderer.
The Nvidia Renderer would appear to be correctly outputting the video as I know the videos are 24fps plus the sound is correct. The MP Renderer would appear to be a problem, yet you say this would be an improvement in video quality.
There is no noticeable degradation of video using the Nvidia option so do you think it would be worth just sticking with this?
What advantage would I get with the MP Renderer?

 

[mm1352000]

Video from the PC is 50fps to the Pioneer TV

Yes, that's currently true. However, it is not something that is fixed in stone. The output frame rate is configurable. Refer to:
http://wiki.team-mediaportal.com/1_...figuration/11_General/21_Dynamic_Refresh_Rate

and when videos are playing it changes to 25fps using MP Audio Renderer

davidf has given you an excellent explanation of what the MPAR is doing and why. I don't think I can explain better, but maybe different words will help...

In an ideal world, best practise is to set the PC output frame rate to match the source (video file, DVD, whatever) fps. That way you get "perfect" video playback. When I say "perfect" I mean that no frames are dropped or repeated.

When you play a 23.976 fps music video on your setup, MediaPortal tries to adjust the PC output frame rate to 23.976 fps to match (as per the "ideal world" principle given above). This adjustment fails because your TV doesn't support the 23.976 fps refresh rate. MPAR does not change the refresh rate to 25 fps. Rather, that is the setting that your TV is using. What MPAR is trying to do is match the TV's actual refresh rate to give the best possible video quality. The trade-off for having better video quality is the increased audio "BPM" which you noticed.

and 24fps using the Nvidia Renderer.

This statement is not correct for the reasons that davidf already explained in his previous post.

The Nvidia Renderer would appear to be correctly outputting the video as I know the videos are 24fps plus the sound is correct.

This statement is partially correct and partially incorrect.

First, let's be clear. Based on what I saw in your log files, some of the music videos are 23.976 fps; others are 25 (50) fps. Note that 23.976 fps is not 24 fps. They are not the same thing, and the difference is significant.

Second: the NVidia renderer is "correctly outputting" the audio... however, the video output is slightly compromised. Compromised in that some frames will be displayed twice, which may be observed as a slightly jerks or micro-stutters in the video.

You could think of the situation this way...
It is impossible for you to get perfect video and audio output for 23.976 fps content because your TV doesn't support the 23.976 fps refresh rate.
You can only get perfection with video or audio.
Different renderers give you different trade-offs.
As explained above, the NVidia renderer compromises video quality in favour of audio quality.
MPAR does the opposite, compromising audio quality in favour of video quality.
You have to choose which compromise you will take.

There is no noticeable degradation of video using the Nvidia option so do you think it would be worth just sticking with this?

Ultimately everything is your choice.
If you don't notice the loss in video quality when using the NVidia renderer then it is okay to use it... but be aware that there is a degradation.

What advantage would I get with the MP Renderer?

As above: no dropped or repeated video frames.


Two final points.

1. This issue only affects content/sources when your TV doesn't support the content's refresh rate. In other words, 23.976 fps content is affected; 25 fps content is not. Currently we don't know for sure whether 24 fps content would be affected. However, if your TV is relatively modern it is likely that it supports 24 fps (for Blu-Rays).

2. On that same line of thinking: assuming that your TV does support 24 fps, davidf has recommended you try adjusting your MediaPortal dynamic refresh rate settings to use 24 fps instead of 23.976 fps. Why would you want to try that? Well, if successful, that adjustment would significantly reduce the "increased BPM" effect when using MPAR. So, you would get perfect video (ie. better than using NVidia) and 99.9% perfect audio. Note that the reason the adjustment is effective is that 24 fps is a closer match to 23.976 fps than 25 fps is:

100 x 23.976 / 25 fps = 95.904 % accurate matching
100 x 23.976 / 24 fps = 99.9 % accurate matching

 

[technoweary]

Hi Guys,
Thank you so much for your help, I do see what you say, and I have watched video, TV and Movie output so much and I am convinced that the MP Renderer does actually give a smoother replay than Nvidia, as you say it should.
But why is it doing this? Where is it getting the idea that 25fps is better than 24fps?
Would it be that the Nvidia drivers are telling it that it's a PAL display and therefor 50Hz / 25Hz.
Is there a way to "force" the Dynamic Refresh to use 24fps regardless of what Nvidia says?
Maybe I did not adjust the Dynamic Refresh settings correctly, I simply overwrote the 23.976fps with 24fps, is that correct?
I do not have much in the way of adjustments on the TV, just 75Hz or 100Hz. There is 72Hz, (3 x 24fps?), but only on PC input and no 1080.
In the TV specs I see that 1080p has a 24fps rate and I was considering forcing the Nvidia driver to this setting but I wonder if this may have a negative effect DVB-T.
I will try 1080p on the weekend and see what success I get.
Thanks again for your help, it is very much appreciated as I am sure you have both got better things to do than give this your attention. ( I feel sure lesser people would have told me where to stick my videos by now!!).
Regards

 

[davidf]

Ideally you want to match the refresh rate of your TV to the fps of your video file. MP uses Dynamic Refresh Rate to determine the fps in the video you are about to play and asks windows to change the refresh rate to match (via the configuration in Mediaportal where you tell it what refresh rate to use for the fps in the video file). You don't want to force any particular rate, but as you generally watch PAL (25 fps material) then the default should be 50hz. Whenever you are about to play any video in Mediaportal it will check the fps in the video against the table you fill in in configuration and change the refresh rate appropriately (MP asks windows and windows asks the Nvidia drivers). Any multiple of the desired rate is fine - although for PAL use 50 or 100 if available as pal is actually 50fps with alternate lines (go to the video configuration in windows and press advanced and it will have a list of all supported rates -use that to fill in the configuration in Mediaportal to get the best combinations. mm has given you the wiki link with the details).

When you play a video file in windows it just uses the refresh rate which is in place it doesn't try to match to source... NVidia just provide the drivers, so has no say in the matter - as you say it just knows it's a display which supports certain refresh rates and nothing about the video file playing.

If you are using an HDMI lead check in the display properties which refresh rates are supported - PC input tends to be different. You just need to fill in the Dynamic Refresh Rate section of Mediaportal Configuration with frequencies your TV supports and are very close to the possible values (all of which are in the configuration).

 

[mm1352000]

Short and direct answers to your questions (since davidf has already given a good answer, again )...

But why is it doing this?

Because that is what it is designed to do!

Where is it getting the idea that 25fps is better than 24fps?

MPAR does not think that 25 fps is inherently better than 24 fps. Rather, as I explained in my previous post: it is just doing what it is designed to do, which is to match the refresh rate of your TV (which is 25/50 fps) so that you get perfect video playback.

Is there a way to "force" the Dynamic Refresh to use 24fps regardless of what Nvidia says?

If your TV supports 24 fps then the NVidia drivers (and Windows, and MP) should recognise that, and therefore you shouldn't have to force anything.
If your TV does not support 24 fps then you can't force it to work.

In the TV specs I see that 1080p has a 24fps rate and I was considering forcing the Nvidia driver to this setting but I wonder if this may have a negative effect DVB-T.

IMHO you should not be forcing the NVidia driver to anything at the Windows level. Stick to MediaPortal's dynamic refresh rate configuration.

As davidf explained: MediaPortal will tell the TV to use the refresh rate you configure for the corresponding content frame rate. That means you can ensure the TV uses the correct (or in the case of 23.976 fps content: best possible) refresh rate for each content frame rate.

Based on what you've told us, your optimal settings would be to configure the TV to use 24 fps for 23.976 and 24 fps (Blu-Ray) content, and 50 fps for 25/50 fps (PAL, UK DVB-S/T/T2 TV) content.

 

[kiwijunglist]

As explained above:

Mediaportal Configuration -> General -> Dynamic Refresh Rate

Change:
Name: CINEMA Frame Rate: 23.976 Refresh Rate: 23

To:
Name: CINEMA Frame Rate: 23.976 Refresh Rate: 24

This is based on the assumption that your display/gpu combination can do 1080p24 but can't do 1080p23 (aka 23.976hz)