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     40 >Video for Linux Two API Specification: Revision 0.24</TH
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     75 ><A
     76 NAME="STREAMING-PAR"
     77 >1.12. Streaming Parameters</A
     78 ></H1
     79 ><P
     80 >Streaming parameters are intended to optimize the video
     81 capture process as well as I/O. Presently applications can request a
     82 high quality capture mode with the <A
     83 HREF="r11680.htm"
     84 ><CODE
     85 CLASS="CONSTANT"
     86 >VIDIOC_S_PARM</CODE
     87 ></A
     88 > ioctl.</P
     89 ><P
     90 >The current video standard determines a nominal number of
     91 frames per second. If less than this number of frames is to be
     92 captured or output, applications can request frame skipping or
     93 duplicating on the driver side. This is especially useful when using
     94 the <A
     95 HREF="r14264.htm"
     96 ><CODE
     97 CLASS="FUNCTION"
     98 >read()</CODE
     99 ></A
    100 > or <A
    101 HREF="r14496.htm"
    102 ><CODE
    103 CLASS="FUNCTION"
    104 >write()</CODE
    105 ></A
    106 >, which are not augmented by timestamps
    107 or sequence counters, and to avoid unneccessary data copying.</P
    108 ><P
    109 >Finally these ioctls can be used to determine the number of
    110 buffers used internally by a driver in read/write mode. For
    111 implications see the section discussing the <A
    112 HREF="r14264.htm"
    113 ><CODE
    114 CLASS="FUNCTION"
    115 >read()</CODE
    116 ></A
    117 >
    118 function.</P
    119 ><P
    120 >To get and set the streaming parameters applications call
    121 the <A
    122 HREF="r11680.htm"
    123 ><CODE
    124 CLASS="CONSTANT"
    125 >VIDIOC_G_PARM</CODE
    126 ></A
    127 > and <A
    128 HREF="r11680.htm"
    129 ><CODE
    130 CLASS="CONSTANT"
    131 >VIDIOC_S_PARM</CODE
    132 ></A
    133 > ioctl, respectively. They take
    134 a pointer to a struct&nbsp;<A
    135 HREF="r11680.htm#V4L2-STREAMPARM"
    136 >v4l2_streamparm</A
    137 >, which contains a union holding
    138 separate parameters for input and output devices.</P
    139 ><P
    140 >These ioctls are optional, drivers need not implement
    141 them. If so, they return the <SPAN
    142 CLASS="ERRORCODE"
    143 >EINVAL</SPAN
    144 > error code.</P
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