ViewCast 240E, 450E manual Granularity, Format Horizontal Vertical

Setting Driver Properties

The reference width and height represent the full uncropped size of the incoming video. Your crop settings are interpreted relative to this reference size. For example, if you are capturing 525-line video, with a reference size of 640 x 480, and your crop rectangle is (0, 0, 640, 480), then your video is effectively uncropped. But if you are capturing 625-line video, with a reference size of 768 x 576, the same (0, 0, 640, 480) crop specification truncate the right and bottom edges of the video.

Granularity

Most video data capture formats impose restrictions on the possible width and/or height of the video, referred to as granularity restrictions. For example, the I420 capture format requires that the capture width be a multiple of 4 and the capture height be a multiple of 2.

The granularities for the various color formats are as follows:

Format	Horizontal	Vertical
RGB32	4	1
RGB24	4	1
RGB555	4	1
Greyscale	4	1
YUY2	4	1
UYVY	4	1
I420	4	2
YVU9	4	4
[none]	4	1
[any]	4	4

The Granularity controls show the granularity restrictions for the selected video format, and assist you in choosing crop and output sizes that observe those restrictions.

Figure 58. Capture drop-down list

Because you can set the preview and capture pins to different color formats, they can have different granularities. When you open the Size and Crop tab, the Capture and Preview fields are initialized to the current or most recently used format for the selected pin (Figure 58).

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