[SOLVED] Long usb cable latency

[Fred]

@ril I use Geffen USB over cat 5 extenders for full speed USB extension. There are some cheaper options from hall research.

http://www.hallresearch.com/pa...

[RIL]

@fred thank you !!

Something strange I found maybe you can help... I notice that the latency is not always present ! Not regular...looking the trigger out of the Video In Watcher sometimes you can see 'the cross" tilting. Does it give you some idea ? Thank you very much.

Best,

[Fred]

@ril does this change without the USB extender?

[RIL]

@fred good question !!! Have to check but I'm would say yes... 

So if yes is the answer what makes you think?

(The cable is new by the way)

Thanks !!

[Fred]

@ril quite often you will notice more latency in changing light conditions. Give the camera something bright to film and check the latency.

It could also be that the computer/USB bus is running out of resources.

[RIL]

@fred interesting the light situation..

About the usb bus...what do you exactly mean about resources? And how can be fixed?

Thanks

[RIL]

@fred I did a fast test...no latency in dark conditions. But then I went to this forum page went back to the patch and latency appears !! Has to quit and re open isadora. Then repeated the process with the web page and worked just fine... to much strange. Help  !!  jajaja 

[Fred]

@ril it could well be that your computer is running out of resources. Browsers can eat a large amount of memory, also. If not having other apps open stops the latency don't open other apps. Things like chrome and even word processors can use significant system resources.

[barneybroomer]

What can be is interference with power lines, so on a desk perfectly fine, once in a theater running along other lines it can experience interference

[RIL]

@barneybroomer thanks ! To many options jaja. What it seems to me is that the problem is not the usb extender. I checked again the lights conditions as @fred suggested also the browser and nothing happend.

Being plug to the power suppply on your desk may produce latency?

Best,

[Fred]

@ril how big is the latency?

[RIL]

@fred 3 or 4 seconds when it happens... 

Yesterday I tested during 1 hour with bad light conditions open and close broeser etc... and worked perfect. Very strange vehavior

[barneybroomer]

Wow, 3 to 4 seconds is really long. Does it have this latency without USB extender as well?

[RIL]

@barneybroomer I believe it doesnt...what is very strange is this random behavior 

Could it be some drivers situation? Thanks !

[Fred]

@ril what is the model of webcam and what resolution are you running it a

[RIL]

@fred Logitech C525.  1920x 1280

[Fred]

@ril the camera has a native resolution of 1280 720, can you try run at that and see what results you get. The upscaling means decompressing the incoming h264 stream and then upscaling, not a trivial task. 

[RIL]

@fred thats a very good idea !!! Thanks

[RIL]

Dear @fred   

apparently that was the problem. Also the video looks much more fluid now. Anyway I will leave it running for a long time to rule out any other problems. continued to be concerned with the issues of light and power cables.

It would be interesting to refresh the whole community of the relationships that occur between the different video sources and their respective resolutions, and the best or most appropriate practices when combining video and live capture.

Thank you very much !!

Best,

[Fred]

@ril in general it is much better to run devices at their native resolution. There are tools inside Isadora that can do efficient scaling. This applies to input as well as output, in general running a camera capture, or a projector at a higher resolution than native does not do anything but use extra resources, and upscaling does not really help. Using GPU based scaling, such as in the mapper is a great way to change the size of an image.

Isadora is also natively resolution agnostic, as positions and sizes are percentage based changing resolution of cameras and video projectors (as long as the aspect ratio is the same) won't change your composition.

Definitely with USB cameras that stream the image with h264 upscaling or downscaling via the CPU on capture is an expensive process and also does not do anything for the image.

With cameras that are on auto settings like USB cameras low light will make the camera go to long exposure that can give extra latency.