Playback speed and dropped frames

[nilesschwartz]

I've recently created a DCP on the software. The video was shot 29.97 fps, the DCP (from a MOV file on a Mac) created at 30 fps. Playing the DCP on the DCP-o-matic player in full screen, the image is very slow moving (a lot of dropped frames) but the audio sounds normal. If I shrink the screen size, the video plays decent, but the audio is conspicuously slowed down. I'm a novice here, but curious what I'm doing wrong. Thanks for any advice.

[Carsten]

Only very fast machines can play without dropped frames. This is a DCP-o-matic player issue, your DCP is most likely perfectly okay.
Which version of DCP-o-matic are you using currently?

Note that not every cinema server is able to play a 30fps DCP. You should test it in advance.

Try this:

Bildschirmfoto 2019-07-23 um 18.32.03.png

- Carsten

[nilesschwartz]

Thanks!

[ainsophaur]

I'm having this problem too. My situation is a little different, however.

It's a 4K DCI DCP encoded to 230Mbps.

However, the media is on a server where I can get 600MB read/write. So I should have no problem playing back something of this size.

Decode at lower resolution didn't help me.

Does anyone have any suggestions?

[Carsten]

4k will always stutter in DCP-o-matic player, even at quarter decode resolution. You would probably need the fastest machine available to get decent playback speed.

What you can do is to disable audio playback in prefs - that will make DCP-o-matic player play the image part as fast as possible, but more or less with a 'steady' rate, so you can check at least for discontinuities.

However, if you used a current version of DCP-o-matic to encode the image, it will play on ANY DCI server without issues, as long as you stayed below 230-240Megabit/s. What is the frame rate of your 4k DCP?



- Carsten

[ajitdias]

I also see erratic playback and dropped frames, even when encoded at 50 bitrate.

Playback in Resolve does not exhibit this behavior, even at 200 bitrate.

Is it possible that something is wrong with the player implementation?

I am using a MacBook Pro (2018), 2.6GHz 6-core Intel Core i7.

[Carsten]

The Mac player currently has serious trouble displaying images fast enough. Which player version did you try? Try the latest 2.15.15 and enable OpenGL renderer in prefs. Not sure if it fully works currently.
I did some tests, and, awkwardly, older Macs perform better than the much faster recent machines. There is something about the highres/Retina displays causing this issue. The only workaround currently is to select quarter resolution decode and adjust the playback window to a smaller size.

The encoding bitrate is irrelevant here. 2k vs. 4k is the only major aspect of encoding that would generally slow down playback.


- Carsten

[binba]

Yeah, the effort to develop a free (/ donationware) Mac DCP player is valiant, but still more work to be done. It's something about the graphics output API, not the J2K decoding. I wonder if it'll take writing it in Metal to make it work well.
My machine manages to play 2K DCPs at full-rez decode quality - if the window is shrunk. And conversely, if I play at quarter-rez decode quality with the window maximized on my 1920x1200 monitor, it's dropping frames like there's no tomorrow. In addition, hitting "Play" always results in 15 seconds or more of severe stuttering until playback stabilizes.

Mac Pro(5,1) 8-core 2.66GHz, 32GB RAM, Radeon RX580, OS X 10.13.6.
Tested with a 100Mbps 2K 2D SMPTE DCP w/ 6 audio channels, and nothing else.

PS There is no option to enable OpenGL in the preferences.

[Carsten]

There is no option to enable OpenGL in the preferences.

Should be available in 2.15.x:

Bildschirmfoto 2019-09-04 um 12.19.07.png

[binba]

My bad. I missed the "try the latest" version, and worked with the release.
I tried the test release with OpenGL, and can report that on my system I'm seeing the same exact behavior with no change: playback performance is dependent on the window size on the screen, not the J2K decode resolution.