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uvc command


uvc - Interface to UVC cameras using libuvc


package require tcluvc
uvc option ?arg ...?


This command provides several operations to interface UVC USB cameras using the infrastructure provided by libuvc and libusb which is available on common Linux, FreeBSD, and MacOSX platforms and sometimes found working on Android devices. option indicates what to carry out. Any unique abbreviation for option is acceptable. The valid options are:

uvc close devid

Closes the device identified by devid which has been opened before using uvc open.

uvc convmode devid ?flag?

Reports or modifies the conversion mode for frames acquired from the opened device identified by devid. Conversion mode 1 (on/true) performs frame format/color space conversions in the special UVC thread which controls the USB transfers, mode 0 (off/false) does this instead in the normal Tcl event loop. The default mode is 1.

uvc counters devid

Reports a three element list of statistic counters on the device identified by devid. The first element is the number of video frames received, the second the number of video frames processed with uvc image, and the third the number of video frames dropped.

uvc devices

Returns device information which can be used for uvc open as a list. Each device adds three elements to the list: the first element is the device name as a colon separated string with two or three fields being vendor ID (hexadecimal, 0x prefix is optional), product ID (hexadecimal, 0x prefix is optional), and bus/device numbers separated by a dot; the second and third list elements are the vendor name, and the product name. To open the device, its name (the colon separated string) must be used, the other two items are available for presentation purposes. If udev support is available (Linux specific), this list is refreshed on plug and unplug of devices. Otherwise, the list is a snapshot of suitable devices currently connected.

uvc format devid ?index fps?

Returns or changes the frame format of the device identified by devid. The optional parameter index is an integer number giving the index of the frame format returned in uvc listformats. The optional parameter fps is the frame rate. If omitted, the currently active index and frame rate are returned. Changing the frame format and rate is only possible if the device is not capturing images.

uvc greyshift devid ?shift?

Returns or sets the bit shift to be applied on grey images with a bit depth higher than 8 which are captured from device devid. The default value is 4, which is suitable for greyscale cameras with 12 bit resolution. The shift is not applied when the image subcommand retrieves raw byte array data.

uvc image devid ?photoImage?

Copies the most recent captured image of the device devid into the photo image identified by photoImage and returns non-zero on success or zero if no data transfer has taken place. If photoImage is omitted, a four element list is returned with the first element being the image width, the second the image height, the third the number of bytes per pixel, and the last the image's RGB values with 3 bytes per pixel in red, green, blue order as a byte array. In this case an error is indicated by throwing an exception.

uvc info ?devid?

Returns information on open devices. If devid is specified, a list of two elements is returned, the first being the device nameand the second the image callback command for that device, i.e. the same arguments which were used on uvc open. If devid is omitted, a list of devids, i.e. all currently opened devices is returned.

uvc listen ?callback?

Retrieves or sets the callback command called on plug and unplug of devices. When a device is plugged or unplugged that callback is invoked with two additional arguments: the type of event (add or remove) and the device name (see uvc devices for the naming convention) which was added or removed. Only usable if udev support is available.

uvc listformats devid

Returns a dictionary keyed by a format index as integer with the values being another dictionary with information about the frame size and rate of the respective frame format. The returned indices can be used in in uvc format to switch to another frame size and/or to change the frame rate.

uvc mbcopy bytearray1 bytearray2 mask

Copies the content of RGB byte array bytearray2 into the byte array bytearray1 using an RGB mask. Both byte arrays must have identical length which must be a multiple of 3 (for RGB). The main purpose of this command is to combine images from two cameras into an anaglyph 3D, where (for a red-cyan anaglyph) the left camera image uses mask 0xFF0000 (red component) and the right camera image uses mask 0x00FFFF (green and blue components).

uvc mcopy photo1 photo2 mask

Copies the content of the photo image photo2 into the photo image photo1 using an ARGB mask. Both photo images must have identical width, height, and depth. The main purpose of this command is to combine images from two cameras into an anaglyph 3D, where (for a red-cyan anaglyph) the left camera image uses mask 0x00FF0000 (red component) and the right camera image uses mask 0x0000FFFF (green and blue components).

uvc mirror devid ?x y?

Retrieves or sets flags to mirror captured images along the X or Y axis. Parameters x and y if specified must be boolean values.

uvc open devname callback

Opens the device with device name devname and establishes callback as command to be invoked on captured images and finally returns a devid, i.e. a handle to further deal with the device. An additional parameter is appended when callback is invoked: the devid of the device. For the format of devname see the description of uvc devices.

uvc orientation devid ?degrees?

Retrieves or sets the orientation of captured images regarding image rotation. degrees if specified must be an integer number.

uvc parameters devid ?key value ...?

Returns or changes device parameters for the device identified by devid given as key-value pairs, e.g. brightness 100 will change the brightness setting of captured images to the device dependent value 100. The command returns the current device parameters (after the potential change, when keys and values were given) as a key-value list which can be processed with array set or dict get.

uvc record devid frame width height bpp bytearray

Transcodes the frame described by width, height, bpp, and bytearray to JPEG and writes the result to the recording file or stream. The recording must have been started with the -user option. An integer number is returned as result: 1 indicates successful write, 0 no write due to frame rate constraints, and -1 an error during the write.

uvc record devid pause

Pauses recording to a file or stream.

uvc record devid resume

Continues recording to a file or stream.

uvc record devid start options ...

Starts recording to a file or stream. options control the data format, frames per second, and output channel. The option -fps specifies the approximate rate in frames per second as a floating point number. The option -chan specifies the channel to which the frames are written. This channel is detached from the Tcl interpreter and controlled solely by the uvc record command. The -boundary option specifies a MIME multipart boundary string and selects the MIME type multipart/x-mixed-replace suitable for streaming to a web browser. The content type delivered to the browser is image/jpeg. If the -boundary option is omitted, the output format is raw AVI and requires the channel to be seekable. The option -mjpeg forces the recorded data to JPEG format, i.e. a transcoding to JPEG will be performed in software, if the device doesn't already deliver a JPEG stream. The option -user turns off automatic frame write operations to the recording file or stream when a frame is delivered from the device. Instead, uvc record devid frame must be invoked in the callback function. The -user option implies -mjpeg.

uvc record devid state

Returns the current recording state as stop, recording, pause, or error. The state error indicates a write error on the file or stream. In this case no further frames will be written.

uvc record devid stop

Finishes recording to a file or stream and closes the underlying channel.

uvc start devid

Starts capturing images of the device identified by devid. When an image is ready, the callback command set on uvc open is invoked.

uvc state devid

Returns the image capture state of the device identified by devid. The result is the string capture if the device is started, stopped if the device is stopped, or error if an error has been detected while image capture was active.

uvc stop devid

Stop capturing images of the device identified by devid.

uvc tophoto width height bpp bytearray ?rot mirrorx mirrory?

Makes the RGB (bpp is 3) or gray (bpp is 1) byte array bytearray of width times height pixels into a Tk photo image. Optionally, the data is rotated by rot degrees (possible values 0, 90, 180, 270) and/or mirrored along the X and/or Y axis as specified by the boolean values mirrorx and mirrory.

The uvc command tries to lazy load Tk, thus allowing to use it from a normal tclsh. Only when a photo image is required by a subcommand, Tk must be available and an attempt to load it is made.