Video for Linux 2
Isis software documentation
Video for Linux 2
Video for Linux 2
(V4L2) is a library for doing video capture on the Linux operating
system. Isis provides a simplified interface to V4L2 for doing video
capture. More documentation will be added later. Below is a summary of
the available functions.
Also be sure to look at the Isis video
capture library which is the best choice for common needs. This
simpler higher-level library uses Video for Linux 2 for is low level
operations.
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(vcap-open port)
# initialize video capture on specified isis port
# which should be open for reading and writing (open-update device),
# returns vc (capture handle) to use in later functions
(vcap-close vc)
# close specified capture handle
(vcap-input vc inputnum)
# change input (integer numbered from 0)
# returns actual input granted
(vcap-format vc framesize pixelformat fieldmode)
# change capture format
# framesize should be [ width height ]
# pixelformat should be one of:
# vcap-rgb32, vcap-bgr32, vcap-rgb24,
# vcap-bgr24, vcap-grey, vcap-yuyv, vcap-uyvy
# fieldmode should be one of:
# vcap-field-interlaced, vcap-field-top,
# vcap-field-bottom, vcap-field-both, vcap-field-any
# returns actual format granted:
# [ framesize pixelformat fieldmode ]
(vcap-period vc)
# returns current frame period in seconds
(vcap-standards vc input)
# returns a list of standards supported by the specified input
(vcap-standard vc standard)
# change video standard
# standard should be a string, such as "ntsc", "pal" or "secam"
# call vcap-standards for a list of supported standards
# returns True if successful
(vcap-start vc)
# start capturing
# returns list of buffer addresses that will be used
(vcap-read vc)
# requeue the previously read buffer (if not done already by vcap-queue)
# and read a new frame
# returns [ bufnum bufaddr bytesused topfield-flag secs microsecs ]
# bufnum is the index of the buffer being returned
# bufaddr is the raw memory address of the data
# bytesused is the number of bytes filled in the buffer
# topfield-flag is True if the frame is the top field
# secs & microsecs is the Unix timestamp of the frame
# (similar to what is returned by (get-time) in Isis)
# the returned buffer is valid for processing
# until the next vcap-queue or vcap-read call
(vcap-image vc framesize pixelformat bufaddr)
# returns an Isis image buffer that refers to the memory in a
# video capture buffer at the address specified by bufaddr,
# in the format specified by framesize and pixelformat,
# which should be the same as returned by vcap-format
(vcap-queue vc)
# place the previously read buffer back in the read queue
# calling this function is optional, for extra efficiency
# vcap-read performs the same action
(vcap-stop vc)
# stop capturing
(vcap-find-control vc control-name)
# find information about a control on the specified capture device
# control-name should be a string, such as "Brightness" or "Contrast"
# if successful, returns a list of 5 integers
# [ control-id minimum-val maximum-val step-val default-val ]
# or Null if the control could not be found
(vcap-control vc control-id)
# gets the value of a control
# control-id is an integer that was determined from vcap-find-control
# returns the integer value of the control
(vcap-control vc control-id value)
# sets the value of a control
# control-id is an integer that was determined from vcap-find-control
# value is the integer value you wish to set the control to
# returns the value the control was actually set to
(vcap-tuner vc input)
# gets information about the tuner for the specified input
# more documentation to come
(vcap-freq vc input)
# gets the current frequency set on the specified tuner
# returns an integer expressing the frequency in units of 62.5 KHz
(vcap-tune vc input frequency)
# sets the frequency on the specified tuner
# frequency should be an integer in units of 62.5 KHz
# returns the actual frequency tuned
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Requirements:
| Scripts:
| (load "v4l2-utilities.isis")
|
| Other:
| Needs Video for Linux 2 library
|