Image Pipe Daemon 1.0
Exposure time is the effective length of time that your camera sensor integrates the scene's light. In simple works, exposure time is the length of time that your image sensor ’sees’ the scene you’re attempting to capture.
The longer the exposure time, the more light reaches the camera's sensor, and vice versa. If the camera sensor doesn't get enough light you end up with a photo which is dark (underexposed). Too much light and your photo comes out bright (overexposed).
It must be noted that large values of exposure time can reduce significantly the video frame rate.
Gain is a multiplication factor applied to each pixel in the image. The camera sensors and the video image processors often offers hardware's controls capable of adjust the gain value. Generally, the gain can be specified independently for each color channel (RGB) or as a global gain applied to all the color channels. When your image colors looks wrong you can use gain to compensate the effect of the scene illumination. Also the the global gain can be increased to improve the image luminance when capturing images under low light conditions. . However, it must be noted that increasing the gain also increases the noise.
- Set previewer mode
- The previewer is used for accessing the image tuning capabilities of the hardware. The previewer hardware includes many modules. The previewer operates in 2 modes: continuous and single shot. In the continuous mode the modules are chained in the capture data path and does image tuning on the fly. In the single shot mode the modules are configured to tune the image stored in the SDRAM.
ipipe-client's command to set the previewer mode is set-previewer-mode.
- Set Bayer pattern
- When you capture raw data the previewer is going to spec a specific order for the Bayer pattern. The default pattern for RidgeRun sdk is GrRBGb. If your sensor gives a different order of Bayer pattern you can define it to the previewer using this function. The change to the input color pattern is not updated during the previewer operation.
ipipe-client's command to define the Bayer pattern is set-bayer-pattern.
- Set/Get gain
- The dm365 ipipe provides a hardware module that executes white balance to each color component. This module includes a gain and offset adjustment. In the white balance gain adjuster, the raw data is multiplied by a selected gain corresponding to color. In the offset adjuster, the raw data is added by the selected offset corresponding to color. The ipiped offers a function to control the gain adjuster, the offset values are kept in zero. Each gain component can range from 0 to 15.998 in steps in steps of 1/512.
- Set/Get luminance adjustment
- Allows to control the brightness and the contrast of the image. The brightness of the video could be adjusted by a dm36x's hardware module. Higher brightness will make the picture more bright. The side effect of higher brightness is the picture looks foggy. The contrast of the video could be adjusted by a dm36x's hardware module. Higher contrast will make the picture sharp. Both adjustments are applied to the luminance component(Y) on the YUV color space. These adjustments are described by the equation Yctr_ brt = (Y x C) + Br, where C is the contrast factor and Br is the brightness factor. Br is an integer value that can range from 0 to 255 and C is float value that can range from 0 to 15.94.
- Set/Get gain
- This sensor can adjusts analog and digital gain. By default the sensor will use analog gain up to its maximum before applying digital gain to the pixels. The ipiped offers functions to set the gain independently for each color channel and to get the current gain values. Each gain component can range from 0 to 128 in steps of 0.125 if gain is between 1 and 4, 0.250 if gain is between 4.25 and 8, and 1.000 if gain is between 8 and 128.
- Set/Get exposure time
- Ipiped offers functions to define the exposure time and get the current exposure time. The unit used for the exposure time is micro-seconds(us). You must take into account that RidgeRun's mt9p031/mt9011
- Flip image vertically and horizontally
- mt9p031 and mt9011 sensors have the capability of flipping the image's columns and rows. Actually these sensors do a image mirror, reversing the readout order. This is going to affect the Bayer pattern order and the resulting colors. If you are using the dm365 video processor, ipiped offers a function to correct the pattern, see Functions for dm365.
The ipiped provides four commands to get access to librraew:
- Init aew
Ipipe-client's command is init-aew
- Stop aew
Ipiped must run in background. If you are using RidgeRun's SDK and enabled ipiped it will be setup to start automatically when the system boots.
ipiped &
Ipiped registers with D-Bus and waits until ipipe-client requests to execute a method.
Ipipe-client is a Dbus client that use commands to invoke methods of the ipiped, so ipiped must be running to use ipipe-client. A command can required arguments depending of the functionality. Ipipe-client has two operation modes, you can ask to execute a single command or you can open an interactive console to execute a group of commands.
To execute a single command, you can use the following command line syntax
ipipe-client <command> <argument 1> ... <argument n>
To get into the interactive console, you have to run ipipe-client without any command. Then to execute a command you only need to use the command and the required arguments.
ipipe-client ipipe-client$ <command 1> <argument 1> ... <argument n> ipipe-client$ <command 2> <argument 1> ... <argument n>To quit the interactive console you can use quit or exit.
In order to know the commands that are available run:
ipipe-client helpor get into the interactive console and execute help.
This shows a description of each command, as follows:
Command Description help Displays the help text for all the possible commands or a specific command. set-debug Enable/Disable debug messages. init-aew Initialize AEW algorithms. stop-aew End AEW algorithm. shell Execute a shell command(shell_cmd) using interactive console. ping Show if ipipe-daemon is alive. quit Quit from the interactive console. exit Exit from the interactive console. get-video-processor Show the video processor that is being used. get-sensor Show the sensor that is being used. run-config-script Execute a group of ipipe-client commands. set-previewer-mode Configure previewer on continuous or one-shot mode. set-bayer-pattern Sets R/Gr/Gb/B color pattern to the previewer. set-digital-gain Sets red (R), green (G) and blue gains (G) on the ipipe. get-digital-gain Returns the gain value for each color component(RGB). set-luminance Brightness(Br) and contrast(C) adjustment. get-luminance Returns the value of the Brightness(Br) and contrast(C) adjustment. flip-vertical Flips the image vertically(on the sensor). flip-horizontal Flips the image horizontally (on the sensor). set-exposure Sets the effective shutter time of the sensor for the light integration. get-exposure Gets the exposure time of the sensor in us. set-sensor-gain Sets red(R), green(G) and blue(B) gain directly on the sensor. get-sensor-gain Gets sensor red(R), green(G) and blue(B).
If you want more detailed information about a command execute:
ipipe-client help <command>
Auto exposure and auto white balance adjustments can be started with an ipipe-client's command called init-aew. Init-aew requires some arguments to define the algorithms and other parameters. To see the arguments required you can request for help that show you the list as follows:
Command: init-aew
Syntax: init-aew <WB> <AE> <G> <EM> <T[us]> <fps> <seg> <width> <height>
Description: Initialize AEW algorithms
Arguments:
WB: white balance algorithm, the options are:
G -for gray world algorithm
W -for retinex algorithm
W2 -for variant of retinex algorithm
N -for none
AE: auto exposure algorithm, the options are
EC -for electronic centric
N -for none
G: gain type, the options are:
S -to use the sensor gain
D -to use the digital
EM: exposure metering method, the options are:
P -for partial metering that take into account the light
information of a portion in the center and the rest of
the frame is ignored. The size of the center depends of
of the parameter center_percentage
C -for center weighted metering that take into account
the light information coming from the entire frame with
emphasis placed on the center area
A -for average metering that take into account the light
information from the entire frame without weighting
SG -for segmented metering that divides the frame
on 6 pieces and weighting them to avoid backlighting
T: wait time in us, specifies the time between
algorithm adjustments, max value=1s=1000000us
fps: minimum frame rate
seg: frame segmentation factor, each frame is segmented into
regions, this factor represents the percentage of the
maximum number of possible regions
width: captured video/image horizontal size
height: captured video/image vertical size
center_percentage: defines the percentage of the image width
and height to be used as the center size
Also you can stop automatic adjustments with the command stop-aew
Some of the init-aew arguments need to be explained in more detail:
- T: the time between interactions defines how fast the algorithm can adjust the scene parameters. If you don't need fast changes you can use a greater time to get less CPU usage.
- seg: this factor is related with the amount of CPU usage and the auto-adjustments precision. If you use a high segmentation percentage you will have greater CPU usage but you will get more precision on the adjustments.
ipipe-client run-config-script dm365_mt9p031_config ipipe-client init-aew G EC S C 200000 30 50 640 480 50
The first command will chain the ipiped using an existing script. The second one will start the auto-white balance and the auto-exposure algorithms for an image size of 640x480 pixels and a minimum frame rate of 30fps.
Once you have the ipiped and the AEW algorithms running you can run any image/video capture GStreamer pipeline to test it.