Skipping, jerky capture video

[cuivenion]

I recently acquired a Logitech Quickcam Pro 4000 with 1.25" inch telescope mod, I tried it out this morning with the telescope and took some video of a seagull on top of a chimney to test it. Everything seemed to run fine until I started the video capture, when the video became choppy as if skipping frames. The video was recording this way as well. Anyone got any ideas?

[Cornelius Varley]

Probably the computer was unable to keep up with the frame rate and was dropping frames (more data being downloaded from the camera than the computer could handle). 

[Stargazer33]

What capture software were you using? Generally with webcams you need to limit the FPS (frames per second) to 5 - 10. Otherwise, as Peter says, the computer just can't keep up with the throughput.

Unfortunately this also means that you capture less 'good' frames during those brief moments of clarity. This means longer image runs than you would need with a high frame rate camera.

[cuivenion]

I was using Craterlet. The laptop is a bit long in the tooth, 1.6ghz dual core 2gb ram about 6-7 years old.

[RichM63]

Why not try a comparison test with SharpCap 2 ?

Download SharpCap

[jgs001]

The laptop should be fine... I do high frame rate video (30 to 40 fps) with my QHY5v on a 10 year old laptop... Make sure that the camera is plugged in directly to the computer, no hubs etc. Make sure you're recording to the internal hard drive (I had to add a second drive in the media bay for the IDE connection, as I was short on storage), and not to a USB drive... the USB read and writes are too slow to handle the streamed video. Otherwise, as said, slow down the frame rate on the webcam.

[cuivenion]

Why not try a comparison test with SharpCap 2 ?

Download SharpCap

I'll give it a go, thanks for the reply's.

[glowingturnip]

check you haven't totally filled up the hard drive too - I have a couple of times now, and it gives similar symptoms

[cuivenion]

check you haven't totally filled up the hard drive too - I have a couple of times now, and it gives similar symptoms)

Nah definately not that. It's 1Tb HDD with about 400gb left. I was at 640x480 at the max framerate (30 fps) so maybe the computer couldn't handle it. Will I need 640x480 when imaging the moon and planets?

[Knight of Clear Skies]

I get this problem as well whenever I've tried webcam imaging. It's not a major problem as it records most of the frames it should, but it does have some impact on the final image quality.

When planetary imaging you may be able to set a region of interest smaller than the sensor size, which will reduce the frame capture size and the work the laptop has to do. This should boost the recorded  frame rate.

[Stargazer33]

Why not try a comparison test with SharpCap 2 ?

Download SharpCap

I used to use SharpCap with my SPC900. It always performed very well I thought.

[toxic]

make sure you are using a usb 2 post and not a usb 1 as the usb 1 is way to slow and will cause stream lag or frame dropping and your frame rate should be 25 to 30 fps.   

[Cornelius Varley]

The maximum frame rate should not exceed 10 fps. To achieve higher frame rates webcams tend to use video compression to maintain the frame rate, thereby losing data.

[cuivenion]

Had a play with Sharpcap and I'm getting the same results. The frame drops went right down when I lowered the resolution so that must be the problem. I'll have to try it on a more up to date computer and see how I get on.

[uhb1966]

Also make sure that no other applications that are computing intense run in the background.

[uhb1966]

Also make sure that no other applications that are computing intense run in the background.

...especially no virus scanners doing a scan at capture time!

[RichM63]

10 fps @ 640x480, YUY2 works for me even though the camera has higher available settings.

[cuivenion]

Hoping to get some Saturn, Mars and Moon shots tonight. I'll let you know how I get on.