Lines Matching +full:frame +full:- +full:buffer

1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
4 .. _func-read:
13 v4l2-read - Read from a V4L2 device
18 .. code-block:: c
31    Buffer to be filled
40 descriptor ``fd`` into the buffer starting at ``buf``. The layout of the
41 data in the buffer is discussed in the respective device interface
45 :c:func:`read()` call will provide at most one frame (two fields)
61 :c:func:`read()` never returns a "snapshot" of a buffer being filled.
62 Using a single buffer the driver will stop capturing when the
63 application starts reading the buffer until the read is finished. Thus
65 reading, or the capture rate must fall below the nominal frame rate of
71 keeps capturing into an internal buffer, continuously overwriting the
72 previously, not read frame, and returns the frame being received at the
76 :c:func:`read()` call. The frame being received at :c:func:`read()`
77 time is discarded, returning the following frame instead. Again this
79 nominal frame rate. An example of this model is the video read mode of
83 In the multiple buffer model drivers maintain a ring of internal
84 buffers, automatically advancing to the next free buffer. This allows
100 of data required for one frame. This may happen for example because
101 :c:func:`read()` was interrupted by a signal. On error, -1 is
103 the next read will start at the beginning of a new frame. Possible error
107     Non-blocking I/O has been selected using O_NONBLOCK and no data was