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Device Feedback

Quadro SDI Output PG-03776-001_v06 | 48

9.1.1 Using the GLX/WGL_video_out Extension

Applications that utilize the wglSendPbufferToVideoNV() or

glXSendPbufferToVideoNV()functions within the WGL_video_out or GLX_video_out

extensions should set the bBlock argument to GL_FALSE

in order to queue buffers,

otherwise if blocking is specified, the number queued buffers will always be 1. An

application should then call

wglGetVideoInfoNV()or glxGetVideoInfoNV() in order

to retrieve the number of vertical blanks since the start of video transfers along with the

count of the current buffer being scanned out.

BOOL wglGetVideoInfoNV (HPVIDEODEV hpVideoDevice,

unsigned long *pulCounterOutputVideo,

unsigned long *pulCounterOutputPbuffer);

int glXGetVideoInfoNV(Display *dpy, int screen,

GLXVideoDeviceNV VideoDevice,

unsigned long *pulCounterOutputVideo,

unsigned long *pulCounterOutputPbuffer);

To determine the current number of full buffers queued, an application should subtract

the value of

pulCounterOutputVideo from the value of pulCounterPbuffer returned

from

wglSendPbufferToVideoNV() or glXSendPbufferToVideoNV() as outlined in

Code Listing 37.

Code Listing 37: Determing the Number of Queued Buffers

unsigned long l_ulNumVertBlanks;

unsigned long l_ulNumBufs;

int l_uiNumBufsQueued = 0;

wglGetVideoInfoNV(ghpDevList[0],&l_ulNumBufs,

&l_ulNumVertBlanks);

l_bRes = wglSendPbufferToVideoNV(hpBuf, l_iBufType, &gBufCount,

FALSE);

l_uiNumBufsQueued = gBufCount – l_ulNumBufs;

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SDI Technologies iH30 Especificações Página 53