VirtualDub quick intro

[MarkS]

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

[julian]

Thanks alot Mark good timing
Just got the spc880nc and flashed the firmware to spc900nc which is working with VirtualDub.

[MarkS]

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

[Fay]

Thanks Mark great info!

[Rick]

go 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...

[Fay]

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

[MarkS]

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

[Mac]

Now we just need some decent weather!

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.

[Fay]

That picture is so funny Mac !!!     

[MarkS]

That picture is so funny Mac !!!     

They roam wild just outside Mac's new smallholding.

[Ian]

I think I heard him shouting, "get orff my laaaaand!"

[mickw]

Mac's only got a small holding 
Still, it seems to work 

[The Thing]

My SPC880 is on order. Should be here shortly.

[Ian]

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".

[MarkS]

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