Video Lag

[Chelsea]

Hi,

We are using Qlab video for our show and we are experiencing some lagging issues. We are not quite sure what the problem is. The lagging has been described as video buffering or the video will stop and then speed up to make up the time loss. The lagging is most noticable when we play a video under a transparent image or when we play a video longer then a minute.

Our set up is the following:

iMac High Sierra (10.13.6)
2.7 GHz Intel Core i5 processor
12 GB of RAM
ADM Radeon HD 6770M 512 MB graphics card

The cable run is an 4' HBMI cable from the Mac to an HDMI to Ethernet converter. From the converter is an 150' Cat5 cable to the receiver. The receiver goes to an 50' HBMI cable that plugs into LG TV.

The resolution of both is displays is 1920x1080.

For the video over a transparent image, the file format is .png over .mov.

If anyone has any suggestions, it would much appreciated.

[micpool]

The critical thing will be the codec you are using for the video file.

Is your transparent image color or a black mask?

Mic

[Adrian Meier]

What cind of Codec do you use? I would  prefer to use QuickTime - ProRes 422

[Chelsea]

The file is color.

[micpool]

And what codec does your video file use? (If you aren't sure open it in QTplayer and get info.) Does it have a soundtrack?

On Friday, June 7, 2019 at 5:02:40 PM UTC+1, Chelsea wrote:

The file is color.

[Chelsea]

It says Linear PCM, Apple ProRes 422, and Time Code. Some of the videos have audio and others don't. 

[micpool]

Try transcoding to ProRes Proxy. This pushes less than a third of the data that ProRes 422 uses through your system. If that works, and you want to increase quality you could try ProRes LT which requires double the data of proxy.

Also check the pixel dimensions of your still and video are not larger than required by your output device (e.g projector)

Mic

[Chelsea]

Thank you, we will give it a try.

[Gmail]

Hi Chelsea,

The codec is a good place to look, but I have a couple of questions about your setup.  You mention you are running HDMI through a converter over CAT5 cable.  Conventional wisdom seems to be that HDMI should be run over at least CAT5e or better over CAT 6 for reliable transmission.  That doesn’t account for the poor bufferring behavior you describe, but it’s something to keep in mind.  

Also, you mention one HDMI feed but say ‘both displays’ are 1920 x 1080.  If you have two displays, how are you serving your video to both?  Does the second get video from the first or is it a separate line, or some sort of splitter?  If it’s two separate lines from the Mac, that could account for this kind of behavior.

Lastly if you haven’t yet, you should look at the Preparing your Mac section of the QLab manual.  The Mac is by default set up to do many things that have nothing to do with your show and any overhead that can be reduced can greatly improve performance.   I don’t see what version of QLab you are using but here’s links to the manual for both 3 and 4.

QLab V3

Preparing Your Mac for QLab.

QLab V4

Preparing Your Mac for QLab.

Hope you find a solution quick!!

Mike Post

mdp...@mac.com

http://mdpostdesign.com

(601) 307-8657

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