AVI file time shorter than selected???

[leelee970]

Hi guys, I’m not sure if this should be posted in this section?

I’m having trouble with my QHY5LII and desktop PC.

When I use Sharpcap or Firecapture the same thing happens.

I select an image run of 120 seconds. But the final AVI file says much less (35sec total). Therefore I’m only capturing say 1000 frames instead of 3000 or more.

What is happening and can I improve things?

I do reduce the ROI size to increase the frame rate but it still records less frames and run time than expected. 

Many thanks for any suggestions.

Lee

[knobby]

Is it maybe the shutter speed , if its too low then it becomes impossible to achieve the target frame rate ... Ie if its 1/10 sec. Then it is impossible to get more than 10fps

[leelee970]

Thanks Knobby, but what perplexes me is not so much the lack of captured frames but the fact I select an image run of 120 seconds but it only records much less.

Maybe I've got my Friday brain on?

[Cornelius Varley]

If you record 120sec of AVI video does the capture last 120sec or is the playback duration shorter ? 

[leelee970]

Interesting.

The Avi file properties says 24 secs of video, but I've just run the file in windows media player and time it and the duration IS 120 secs BUT the image pauses several times while the clock ticks giving just 24 seconds of images.

Lee

[Cornelius Varley]

The reason the two are different is because the media player will replay the video are 25 fps whereas the capture frame rate will be much slower.

[glowingturnip]

laptop's not out of hard disc space is it ?  I've had that before, was full up with avis, and then started really stuttering trying to capture, skipping frames, tiny files etc

[leelee970]

Sorry for late reply Stuart, no the HD is not even close to full.

Lee

[SnakeyJ]

I think Cornelius is right, but it doesn't do this with my qhy5l-iim and firecapture. Sixty seconds is recorded regardless of frame rate.

Perhaps a driver error or limitation - do you use the wdm driver or native?

The easy workaround would be to set a target frame limit, rather than time. Though I've always used time, 60s per channel.

[Oddsocks]

Sounds like USB throughput issues that is causing dropped frames, possibly hardware driver for the USB ports, wrong camera driver in use or even antivirus or firewall slowing things down.

Even though the HD has free space have you de-fraged the drive recently?

Image capture will drop frames if the drive is badly fragmented as each new frame arrives before the last one has been written to disk.

FireCapture has some useful tools under  -  "Settings" - "Misc" - "Performance" - that allows you to try writing direct to disk without OS caching, which might help, and also to select the disk buffer size used, if you have a slow HD selecting a large buffer will help, at least for short capture runs.

After carrying out HD defrag then run the FireCapture "disk write test" and then choose the buffer size that gives you the highest frame transfer speed, this will also tell you the best possible frame rate you can achieve with your camera, hardware and driver combination.