iCatch version 0.07
===================

iCatch version 0.07 comes in two flavours, one to work with PCI cards and
one to work with Hauppauge USB capture devices. The names of the two
variants are iCatch_PCI and iCatch_USB respectively.

This split was made in order to clarify the user interface and improve
reliability.


iCatch_USB
==========

This version includes support for USB capture, using a modified Hauppauge
WinTV USB device as described on Steve Chambers' website.

It fixes some bugs that were present in v0.04, which caused the AVI files
to be unreadable :(

It also includes preliminary support for self-guiding mode - however due
to the time taken to capture a frame, it is not anticipated that this mode
will be useful with a USB device.

You will need to put the file EZTw32.dll into the Windows system folder in
order to allow the capture to succeed.

You can choose which device is used for the capture by using the menu option
'Options->Video Source'. Note that the device must be a Hauppauge capture device.



iCatch_PCI
==========

The capture technique for PCI cards has changed slightly from version 0.03, in
an attempt to make iCatch more compatible with other cards and compression
formats.

You can select the video source from the list at the bottom of the 'Options' menu.
Once you have done this yo ucan configure the video driver using the options
'Options->Video Source' and 'Options->Video Format'. You can also choose whether
live video is displayed when not capturing, using the Overlay and Preview options.

In the 'Options->Video Format' dialog you can choose various data formats as well as
image sizes. iCatch will use only 640x480 or 320x240 as the size, and will choose
the nearest to the size specified in the dialog.

iCatch will allow you to use whatever pixel format you like, but you should be aware
that the final image seems only to be produced as 24-bit RGB or 16-bit. The value
that is produced depends on both the format chosen and the screen colour depth,
for some reason. It is best to avoid a 16-bit output because it will show banding 
artefacts as a greyscale. To ensure a 24-bit output, I set the format and screen
depth to 24-bit. However other formats may put less of a burden on the CPU when 
capturing, so may be suitable for slower machines if the output can still be 
generated as 24-bit. Note that of the various compression modes, most will 
preserve the full 8-bits of luminance except for the 15/16-bit RGB mode which 
is best avoided. To determine what bit depth is output, generate a 1-frame AVI 
and look at the file size. Divide the file size by (image width * image height), 
and multiply by 8. The nearest integer will be the number of bits per pixel.


General notes
=============

You can choose between low and high resolution captures by selection the
'Options->Resolution' menu item. 

In Hi-res mode, iCatch will capture at 640x480 in two interleaved chunks. This is
pretty instantaneous with a PCI card, but takes about 6 seconds or so over USB. During
this time it's inadvisable to play with windows, buttons, menu options, etc. since
it can cause the Twain capture dialog to get into a peculiar state. I haven't found a
way to avoid this, sadly.

In Lo-res mode, iCatch produces 320x240 images with a PCI card, and 640x480 with a USB -
but alternate lines are replicated.


Port access
-----------

iCatch requires direct access to the printer port, which is not normally permitted
by Windows NT, XP or 2000. When running with these operating systems you need to use a
special driver which will permit port access. Two such drivers are

PortIO (http://www.direct-io.com/)
Giveio.sys

If you do a search with Google you should find more information
on these. Note that I haven't yet tried them, but I believe that they will allow iCatch
to work.
Windows 95, 98, and ME do not require the use of these drivers.


Guide mode
----------

I've started adding supprt for 'self guiding' in which alternate scanlines can be read
at regular intervals for guiding whilst integrating the remaining scanlines for a long
period. To enable this mode, use the 'Capture->Setup' dialog and choose a suitable guide
interval, say 1000 ms to start with. Check the checkbox to enable guide mode. Now when
capturing you should see a second window open, which will be updated with 1s exposures.
At the end of the main exposure, the main window will be updated with a long exposure.

If you right-click in the guide window near a star, a green box should appear around the
star. In subsequent guide images the green box should remain stationery, and a red box
will be drawn around the nearest star to it. When they coincide, the box will appear yellow.
The idea is to manually (at present) adjust the scope tracking so that the boxes coincide,
in order to compensate for periodic error, drift, etc.

Note that this is a very preliminary feature that has not been tested thoroughly. I intend
to build a serial interface to my scope drive and have the guiding done automatically, but
I wanted to get this release out first.

Also note that guide mode is not very well suited to USB capture due to the longer time
taken to grab a field over USB. This delay will make guiding difficult, and will also
mean that the CCD amplifier is enabled for longer than with a PCI card, resulting in
significant amp-glow effects.


As mentioned earlier, quite a lot has changed inside iCatch since the 0.03 release
so it's possible that errors have crept in. If you have problems with it, you can email
me at jgroveuk@yahoo.co.uk

Have fun,
Jon.

