Image Compression

This is a modified XIL example to which H.261 (video) compression was added. See source code notes for specific H.261 code changes. The SunVideo version of this demonstration program can be run under the SunVideo Binary Compatibility Mode without modification (the SunVideo version does not include H261). Note that the default shrink factor is 2 (-s 2) which results in CIF-sized image compression. To compress QCIF-sized images, use -s 4.

The following shows the command-line syntax for the xil_compress example:

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hostname% xil_compress options -o filename

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The following table describes command options and the default setting

Table 4-5 xil_compress Options

Legal Options	Description and Values	Default
-o %s	Save bitstream in file	NULL
-C %s	Compression type (CellB, JPEG, MPEG1, H261)	CellB
-s %d	Shrink factor	2
-I %d	Select input channel	1
-f %d	Frames to capture	100
-i %d	Frames to skip between capture	0
-D %s	Name of device	/dev/olk0
-B %d	H261 bitrate, kbits/sec	2000
-Q %d	H261 max quantity	10
-R %d	H261 rate control (0=variable, 1=fixed)	1
Legal Switches
-E	Exit on first error

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Example Usage

To compress a CIF CellB bitstream, type:

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hostname% xil_compress -C CellB -o /tmp/t.clb

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To compress a CIF JPEG bitstream, type:

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hostname% xil_compress -C Jpeg -o /tmp/t.jpeg

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To compress a CIF H261 bitstream, type:

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hostname% xil_compress -C H261 -o /tmp/t.h261

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To compress a QCIF H261 bitstream, type:

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hostname% xil_compress -C H261 -s 4 -o /tmp/t.h261

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