xil_cis_get_max_frames(3)

NAME

xil_cis_get_max_frames, xil_cis_set_max_frames, xil_cis_get_keep_frames, xil_cis_set_keep_frames − get or set the upper limit on the number of compressed frames that a CIS should buffer

SYNOPSIS

#include <xil/xil.h>

int xil_cis_get_max_frames (XilCis cis);

void xil_cis_set_max_frames (XilCis cis,

int max_frames_to_buffer);

int xil_cis_get_keep_frames (XilCis cis);

void xil_cis_set_keep_frames (XilCis cis,

int frames_to_keep);

DESCRIPTION

xil_cis_set_max_frames () sets the upper limit on the number of compressed frames that the compressed image sequence (CIS) should buffer. A value of -1 means no limit. The default size depends on the compressor. The setting is a suggestion rather than a requirement, because some compression algorithms may not be able to function reasonably on an arbitrarily small buffer. An error occurs if a call to xil_compress(3), xil_cis_put_bits(3), or xil_cis_put_bits_ptr(3) results in more than max_frames_to_buffer frames in the CIS.

xil_cis_get_max_frames() retrieves the value set as the maximum number of compressed frames that the CIS will buffer at one time.

xil_cis_set_keep_frames() sets the number of frames before the read frame that the CIS should try to retain. A value of -1 means no limit. In general, the number of keep frames should be smaller than the number of max frames.

XIL assigns higher priority to maintaining max_frames than to maintaining keep_frames. Like xil_cis_set_max_frames(), the setting of the maximum number of keep frames is only a suggestion, because some decompression algorithms may not be able to function reasonably unless some set of previously read frames (such as key frames) exists in the CIS.

An error occurs when the number of frames between the start of the CIS and the read position falls below the set number of keep frames due to the addition of frames to the CIS and the CIS’s attempt to keep the maximum number of frames in the entire CIS less than or equal to max_frames.

Seeking backward such that the number of frames before the read position becomes less than the desired keep frame value is not an error.

xil_cis_get_keep_frames() retrieves the value set as the maximum number of frames that the CIS should attempt to keep around.

ERRORS

For a complete list of XIL error messages by number, consult Appendix B of the XIL Programmer’s Guide.

EXAMPLES

XilCis cis;
int mframes, kframes;
xil_cis_set_max_frames(cis , -1);
xil_cis_set_keep_frames(cis , 10);
mframes = xil_cis_get_max_frames(cis);
kframes = xil_cis_get_keep_frames(cis);

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