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\chapter{The Frame Grabber Library}

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The library is divided in 2 layers: the low level and the high level. The first

one is in charge of the acquisition board hardware control and supplies a

generic interface for the higher level. The second layer supplies some API

function for a comunication between the application and a generir video device

(framegrammer, webcam, etc.).

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\section{BTTV low lever driver}

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At the actual stage of developement is the only low lever driver ported from

Linux to S.Ha.R.K. Support acquisition boards based on BookTree BT8x8 chips.

Presents only 2 functions for opening and closing cards.

\vspace{7mm}

\begin{intest}

BTTV26\_INIT\index{BTTV26\_init()}

\end{intest}

\begin{description}

\item [\textbf{int BTTV26\_init(void);}]

\item [\textbf{Description:}] It initializes the acquisition board interface and the

library's internal data

structures.

\end{description}

\begin{intest}

BTTV26\_CLOSE\index{BTTV26\_close()}

\end{intest}

\begin{description}

\item [\textbf{int BTTV26\_close(void);}]

\item [\textbf{Description:}] It close the acquisition board interface.

\end{description}

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\section{VideoDevice high lever interface}

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This library supplies an abstract layer created to obtain a common interface

between different low level driver. The interaction with an application is quite

simple and implies only 2 functions: the first one open the comunication between

the application and the hardware through the low level driver, the second one

send commands to the device.

\vspace{7mm}

\begin{intest}

VIDEODEV26\_OPEN\index{VIDEODEV26\_open()}

\end{intest}

\begin{description}

\item [\textbf{int VIDEODEV26\_open(int num);}]

\item [\textbf{Description:}] It initializes the acquisition board interface and the

library's internal data structures. The parametetr \texttt{num} define the

device that must be opened. \item [Return]value: 0 if the module is installed; 1

otherwise.

\end{description}

\begin{intest}

VIDEODEV26\_IOCTL\index{VIDEODEV26\_ioctl()}

\end{intest}

\begin{description}

\item [\textbf{int VIDEODEV26\_ioctl(int num, unsigned int cmd,

unsigned long arg);}]

\item [\textbf{Description:}] It send the command \texttt{cmd}, with argument

\texttt{arg}, to the device number \texttt{num}. \item [Return]value: It depends

from the command executed.

\end{description}

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\subsection{Video Devices Commands}

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This is a list of most commond videodev commands. Most of them are supported by

the BTTV low lever driver. There is only a major change implemented during the

porting phase: the VIDIOCSYNC function requires an aperiodic task PID as input.

When the new frame is ready, the task is activated.

\vspace{7mm}

\begin{description}

\item [The]full command list is:

\end{description}

VIDIOCSYNC - Synchronize with memory mapped capture.

VIDIOCGCAP - Get video/radio device capabilities.

VIDIOCGCHAN - Get source properties.

VIDIOCSCHAN - Select source and set properties.

VIDIOCGTUNER - Get tuner properties.

VIDIOCSTUNER - Select tuner and set properties.

VIDIOCGPICT - Get video image (picture) properties.

VIDIOCSPICT - Set video image (picture) properties.

VIDIOCCAPTURE - Enable or disable video capturing.

VIDIOCGWIN - Get video output window properties.

VIDIOCSWIN - Set video output properties.

VIDIOCGFBUF - Get direct video output frame buffer properties.

VIDIOCSFBUF - Set direct video output frame buffer properties.

VIDIOCGFREQ - Get tuner frequency property.

VIDIOCSFREQ - Set tuner frequency property (i.e., tune to new frequency).

VIDIOCGAUDIO - Get audio properties.

VIDIOCSAUDIO - Set audio properties.

VIDIOCMCAPTURE - Initiate memory mapped capture.

VIDIOCGMBUF - Get memory mapped buffer properties.

\begin{description}

\item [Example:]

\end{description}

\begin{tt}

\begin{verbatim}

/* Init videodev driver */

VIDEODEV26_open(FRAME_GRABBER_NUMBER);

/* Select the input channel */

res = VIDEODEV26_ioctl(FRAME_GRABBER_NUMBER,VIDIOCGCHAN,(unsigned long)&chan);

chan.channel = channel;

chan.type = VIDEO_VC_TUNER;

chan.norm = VIDEO_TYPE_CAMERA;

res = VIDEODEV26_ioctl(FRAME_GRABBER_NUMBER,VIDIOCSCHAN,(unsigned long)&chan);

/* Enable the tuner */

tuner.tuner = 0;

tuner.mode = VIDEO_MODE_PAL;

res = VIDEODEV26_ioctl(FRAME_GRABBER_NUMBER,VIDIOCSTUNER,(unsigned long)&tuner);

/* Select palette and depth */

res = VIDEODEV26_ioctl(FRAME_GRABBER_NUMBER,VIDIOCGPICT,(unsigned long)&vpic);

#ifdef COLOR

vpic.palette = VIDEO_PALETTE_RGB24;

vpic.depth = 24;

#else

vpic.palette = VIDEO_PALETTE_GREY;

vpic.depth = 8;

#endif

vpic.brightness = 35000;

vpic.hue = 32000;

vpic.contrast = 32000;

vpic.colour = 32000;

res = VIDEODEV26_ioctl(FRAME_GRABBER_NUMBER,VIDIOCSPICT,(unsigned long)&vpic);

/* Set window dimensions */

res = VIDEODEV26_ioctl(FRAME_GRABBER_NUMBER,VIDIOCGWIN,(unsigned long)&win);

win.x = 0;

win.y = 0;

win.width = FG_W;

win.height = FG_H;

res = VIDEODEV26_ioctl(FRAME_GRABBER_NUMBER,VIDIOCSWIN,(unsigned long)&win);

/* Set the buffer */

res = VIDEODEV26_ioctl(FRAME_GRABBER_NUMBER,VIDIOCSFBUF,(unsigned long)(fbuf));

/* IMPORTANT: Set the aperiodic elaboration task */

/* When the new frame is ready, the task elaborate_PID (aperiodic), is activated.*/

VIDEODEV26_ioctl(FRAME_GRABBER_NUMBER,VIDIOCSYNC,(unsigned long)(elaborate_PID));

\end{verbatim}

\end{tt}