There are two types of thumbnails that AVAIL displays for user-created channels;
- the thumbnail that windows provides
- a custom thumbnail produced by having the same filename, but with a JPG, or PNG extension.
Right now, AVAIL asks Windows for a thumbnail, extra large - which equates to 256 x 256 pixels. Windows in turn asks the registered application to provide a thumbnail. The registered file type handler is probably the single greatest influence in the quality of the thumbnail.
You can control the "display size" (some may refer to this as "resolution") of the thumbnails in AVAIL by using the thumbnail scale slider at the top of the interface next to the Details and Thumbnails mode selector.
The actual image resolution being displayed is dictated by the resolution of the thumbnail being provided by the file. AVAIL relies on Windows to provide the thumbnail for each file. Generally, those thumbnails are stored as part of the file and it was up to the application that saved the file to determine the resolution of the thumbnail provided. In other words, default thumbnails will vary in quality depending on the file type.
AVAIL provides a means of overriding the default thumbnail that is generated and stored in the source file itself. Simply save a JPG or PNG image (of any resolution) in the same directory with the same name as the source file and AVAIL will treat that image as the new default thumbnail for that source file. This not only provides the ability to display high resolution thumbnails but also serves to provide high resolution previews in the AVAIL Properties panel.