I've been asked about using VirtualDub to capture long AVI files from a webcam and then edit them. This very brief tutorial is based on the Philips SPC900 Webcam:
First open up VirtualDub!
1) Menu option File|Capture AVI ... to enter capture mode
2) Menu option Device then select Microsoft WDM Image Capture (Win32) (VFW)
3) Menu option File|Set Capture File ... to set the capture file name
4) Menu option Video then tick Preview
5) Menu option Audio then untick Enable Audio Capture
6) Menu option Video|Format
choose 640x480 as Resolution (the native resolution of the CCD)
Choose YUY2 as Pixel depth and compression (this is better quality than the alternatives)
7) Menu option Video|Source
On the Picture Tab:
Untick Full automatic control
Choose frame rate
Switch off auto exposure
Switch off Auto white balance and select "Outdoor"
Slide shutter speed to slowest setting (leftmost)
Increase gain until your planet looks exposed OK
Hit OK
8 ) Menu option Capture|Capture Video - this is now capturing your video. To finish capturing hit Escape key
CHANGE file name (step 3) before you capture another video file!
Registax does not cope very well with huge AVI files so you need to edit a shorter section of video as follows:
1) Menu option File|Open video file to load your big AVI file
2) Menu option Video tick Direct Stream Copy
3) Menu option Audio tick No Audio
4) Use the slider to "preview" the AVI file
5) Use the slider plus left and right arrow buttons to select a short section
6) Menu option File|Save as AVI to save your short section of video (choose a different file name!)
The short video can now be opened in Registax.
Enjoy!
Mark
Thanks alot Mark good timing :D :D
Just got the spc880nc and flashed the firmware to spc900nc which is working with VirtualDub.
One other thing - if your laptop internal drive has little space then record direct to an external hard drive - you can happily create AVI files hours and hours long and hundreds of Gigabytes in size with VirtualDub...
Oh, one more (obvious) thing - try it all out in the comfort of your home in daylight before experimenting outside in the dark!!
Use guiding as well - then you can go off and have a cup of tea whilst recording your planetary/lunar AVI to disk without your planet disappearing off screen.
Mark
Thanks Mark great info!
Quote from: MarkS on Sep 27, 2010, 23:11:44go off and have a cup of tea whilst recording your planetary/lunar AVI to disk
Great for those animations, I presume... ;)
For single images, particularly with a fast-rotating object like Jupiter, there must be an upper limit in time between the first and last frames that contribute to a stacked image, and I'd guess it's shorter than the time I'd take to have a cuppa... ;)
I was going to ask Mark that. How long do you have to take a series of AVI's for stacking into one image. How often do you take a series for a video sequence?
Thanks Mark
If you are using the convenience of a webcam then you really should take advantage of its power - there is no need to stop and change filters (as with mono CCDs) so why not record one single long colour movie. In that way you will not miss the periods when the seeing is at its best. You can then review the AVI at your leisure to find the best sections to pass through Registax. Create short clips from the main AVI using VirtualDub.
So how long should a clip of video be for Registax? My Jupiter image was 300 pixels in diameter on the CCD and the planet rotates in 10 hours. So a surface feature at the middle of the disc shifts 1.5 pixels every minute (since the circumference would be 300*pi i.e. approx 900 pixels - therfore it must rotate by 90 pixels/hour). So a 2 or 3 minute clip is really about the limit for Registax (remember that Registax can do its alignment on surface features). I actually used 3 minute clips for my images. If your image is smaller then you might be able to afford to go a little longer. Another advantage of having the raw movie as one big file is that it allows you to experiment with different clip lengths.
Now we just need some decent weather!
Mark
QuoteNow we just need some decent weather!
(http://whyfiles.org/wp-content/uploads/2010/03/4.jpg)
No chance.............
we're still trying to get over the bad weather from Caroles observatory ;)
and now mine. I'll start looking for 2012 as the first clear skies.
:cheesy:
That picture is so funny Mac !!! :lol: :lol: :lol:
Quote from: Fay
That picture is so funny Mac !!! :lol: :lol: :lol:
They roam wild just outside Mac's new smallholding.
I think I heard him shouting, "get orff my laaaaand!"
Mac's only got a small holding :o
Still, it seems to work ;)
My SPC880 is on order. Should be here shortly.
Quote from: The Thing on Sep 28, 2010, 20:39:56
My SPC880 is on order. Should be here shortly.
ahh, the screeching sound of a thread being dragged back on topic...
I would think the better approach would be to have a small "held by someone else".
One more thing - I am getting better results with Registax 4 than Registax 5 at the moment - I haven't quite worked out why.
Frames from the SPC900 webcam have a kind of subtle "interlacing" noise. It sems to me that at the optimizer stage Registax 5 tends to be aligning frames on this interlacing noise instead of on the surface feature of interest. Registax 4 is doing a better job. Low pass prefiltering at the optimizer stage helps but it doesn't explain why Reg4 is better in the default config.
Mark
I know what you mean Mark. My Jupiter footage with the QHY5 shows a near vertical artifact in some of the sets of frames I took. Its only across the planetary disc. Must be the same sort of thing. I am going to try a different version of the drivers from the astrosurf guys.
Duncan,
According to the July Astronomy Now article you referred me to, almost every camera has some kind of artifact. Trying a different frame rate might (or might not) help.
Mark
The qhy5 software only allows an exposure and an delay to be set. The combination must result in a frame rate. I was using 25ms exposure and a 1ms delay. That would be approx 4 frames per second. I think I should increase the delay and maybe use the slow read option as every now and then the frame 'flares' bright or gets a bright band.
Quote from: The Thing
I was using 25ms exposure and a 1ms delay. That would be approx 4 frames per second.
My maths tells me that's more like 40 fps, not 4.