UsingISC (Image Sensor Controller)

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Introduction

This page describes how to configure and use of the ISC in SAMA5D2 SoC with the image sensors.

• The Image Sensor Controller(ISC) manages incoming data from a sensor up to 12-bit parallel interface.
  • The ISC can generate the isc_mck output clock to the image sensor.
    • The isc_mck clock has three selectable clock sources and one programmable clock divider.
  • The ISC can handle pixel clock up to 96MHz, with the maximum resolution of 2592x1944.
• The ISC includes a video pipeline consist of the following sub-modules:
  • PFE: Parallel Front End to sample the camera sensor input stream
  • WB: Programmable white balance in the Bayer domain
  • CFA: Color filter array interpolation module
  • CC: Programmable color correction
  • GAM: Gamma correction
  • CSC: Programmable color space conversion
  • CBC: Contrast and Brightness control
  • SUB: This module performs YCbCr444 to YCbCr420 chrominance subsampling
  • RLP: This module performs rounding, range limiting and packing of the incoming data
• The sub-modules in video pipeline can handle the following input pixel formats:
  • Raw Bayer convert to YCbCr
  • YCbCr (YCbCr 444, YCbCr 422, YCbCr 420),
  • Luminance (Black and White) Pixel Format.
  • 16 bpp RGB, 32 bpp RGB, 16 bpp.
• For output format,
  • For YCbCr output, the ISC includes a DMA interface which allows YCbCr data organized in packed, semi planar or planar format.
  • It can also convert YCbCr to RGB.
  • It can also be configured as by pass mode, to store original data received from the sensor.

Prerequisites

Starting with Linux Kernel 4.9, we provide and support kernel drivers for ISC.

Starting with Linux Kernel 4.14 (included in Linux4SAM 6.0) , we offer the Device Tree support for the ISC and sensors as an Overlay for the SAMA5D2 Xplained board only. Overlays are required for extension boards, like camera sensors in our case. For more information, visit the DT-overlays page.

Advanced features

Starting with Linux Kernel 4.19 (included in Linux4SAM 6.1) , we offer extended support for the White Balance features.

Configuration in kernel

The ISC driver in Linux kernel provides the upper layer interface to the Video4Linux (V4L2) framework. To make it work, you should enable the following options in Kernel menuconfig.

• Enable V4L2 framework.
  • Under the menu: "Device Drivers ---> Multimedia support"
    
    • Select the menu "Device Drivers ---> Multimedia support ---> Media Controller API"
    • Select the menu "Device Drivers ---> Multimedia support ---> V4L2 sub-device userspace API"
    • Deselect the menu "Device Drivers ---> Multimedia support ---> Autoselect ancillary drivers (tuners, sensors, i2c, spi, frontends)"

Enable ISC and sensor drivers

• Select device driver
  • V4L platform device can be found in the menu: "Device Drivers ---> Multimedia support ---> V4L platform devices"
    
    • Deselect the menu "Device Drivers ---> Multimedia support ---> V4L platform devices ---> SoC camera support"
    • Select the menu "Device Drivers ---> Multimedia support ---> V4L platform devices ---> ATMEL Image Sensor Controller (ISC) support"
• Select sensor driver
  • Sensor drivers can be found in the menu "Device Drivers ---> Multimedia support ---> I2C Encoders, decoders, sensors and other helper chips "
    
  • We have tested with OV7670 , OV7740 and OV5640 image sensors.

Configuration in U-boot

Starting with Linux Kernel 4.14 (included in Linux4SAM 6.0) and U-boot 2018.07 , we offer the Device Tree support for the ISC and sensors as an Overlay for SAMA5D2 Xplained board. Overlays are required for extension boards, like camera sensors in our case. For more information, visit the DT-overlays page.

U-boot, if instructed to do so, will load the Device Tree Overlay for the Image sensor controller (ISC) and the Device Tree Overlay for the specific sensor which we support. Currently, Omnivision ov7670 and ov7740 are supported and only for the SAMA5D2 Xplained board. Starting with Linux Kernel 4.19 (included in Linux4SAM 6.1) we offer support for the Omnivision ov5640 sensor on both the SAMA5D2 Xplained and SAMA5D27 SOM1 EK

To instruct U-boot to load the additional required Device Tree Overlays, proceed with the following steps:

SAMA5D2 Xplained board

• Step 1: The boot command needs to have an additional overlay for the ISC controller itself. This is an additional FIT image overlay configuration:

bootm 0x24000000#kernel_dtb#isc

• Step 2: The boot command needs to have an additional overlay for the sensor. This is an additional FIT image overlay configuration:

bootm 0x24000000#kernel_dtb#isc#ov7670

or

bootm 0x24000000#kernel_dtb#isc#ov7740

or

bootm 0x24000000#kernel_dtb#isc#ov5640

Note that both overlay configurations are required, chained as in the command in step 2 above. the 'isc' overlay will add the setup for the ISC, and the ov7670/ov7740/ov5640 will add the setup for the sensor itself.

The following table summarizes the possible FIT image overlay configurations that are needed:

	Overlay configuration	Effect	Requirements	Starting with Linux4SAM version
Image Sensor Controller	isc	Adds the Image Sensor Controller setup configuration	Base Kernel device Tree Blob 'kernel_dtb' configuration	Linux4SAM 6.0
Omnivision ov7670	ov7670	Adds the Omnivision ov7670 setup configuration	Base Kernel device Tree Blob 'kernel_dtb' configuration and 'isc' configuration	Linux4SAM 6.0
Omnivision ov7740	ov7740	Adds the Omnivision ov7740 setup configuration	Base Kernel device Tree Blob 'kernel_dtb' configuration and 'isc' configuration	Linux4SAM 6.0
Omnivision ov5640	ov5640	Adds the Omnivision ov5640 setup configuration	Base Kernel device Tree Blob 'kernel_dtb' configuration and 'isc' configuration	Linux4SAM 6.1

Note that adding just an overlay for the sensor is not enough. The 'isc' overlay is a mandatory prerequisite .
Note that SAMA5D2 Xplained board is used as a reference, and the software support is created and tested for this board. The SAMA5D2 SoC supports ISC, but to have it up and running, please check your board schematics.

SAMA5D27 SOM1 EK board

This support is only available starting with Linux Kernel 4.19 (included in Linux4SAM 6.1)

• Step 1: The boot command needs to have an additional overlay for the sensor. This is an additional FIT image overlay configuration:

bootm 0x24000000#kernel_dtb#ov5640

Note that only the support for ov5640 is currently available.

The following table summarizes the possible FIT image overlay configurations that are needed:

	Overlay configuration	Effect	Requirements	Starting with Linux4SAM version
Omnivision ov5640	ov5640	Adds the Omnivision ov5640 setup configuration	Base Kernel device Tree Blob 'kernel_dtb' configuration	Linux4SAM 6.1

Note that the connector on this board is different from the one on SAMA5D2 Xplained. Different wiring/extension board are required .
Note that SAMA5D27 SOM1 EK board is used as a reference, and the software support is created and tested for this board. The SAMA5D2 SoC supports ISC, but to have it up and running, please check your board schematics.

SAMA5D27 WLSOM1 EK board

This support is only available starting with Linux4SAM 6.2

* Step 1: The boot command needs to have an additional overlay for the ISC controller itself. This is an additional FIT image overlay configuration:

bootm 0x24000000#kernel_dtb#isc

• Step 2: The boot command needs to have an additional overlay for the sensor. This is an additional FIT image overlay configuration:

bootm 0x24000000#kernel_dtb#isc#ov7670

or

bootm 0x24000000#kernel_dtb#isc#ov7740

or

bootm 0x24000000#kernel_dtb#isc#ov5640

Note that both overlay configurations are required, chained as in the command in step 2 above. the 'isc' overlay will add the setup for the ISC, and the ov7670/ov7740/ov5640 will add the setup for the sensor itself.

The following table summarizes the possible FIT image overlay configurations that are needed:

	Overlay configuration	Effect	Requirements	Starting with Linux4SAM version
Image Sensor Controller	isc	Adds the Image Sensor Controller setup configuration	Base Kernel device Tree Blob 'kernel_dtb' configuration	Linux4SAM 6.2
Omnivision ov7670	ov7670	Adds the Omnivision ov7670 setup configuration	Base Kernel device Tree Blob 'kernel_dtb' configuration and 'isc' configuration	Linux4SAM 6.2
Omnivision ov7740	ov7740	Adds the Omnivision ov7740 setup configuration	Base Kernel device Tree Blob 'kernel_dtb' configuration and 'isc' configuration	Linux4SAM 6.2
Omnivision ov5640	ov5640	Adds the Omnivision ov5640 setup configuration	Base Kernel device Tree Blob 'kernel_dtb' configuration and 'isc' configuration	Linux4SAM 6.2

Note that the connector on this board is different from the one on SAMA5D2 Xplained. Different wiring/extension board are required .
Note that SAMA5D27 WLSOM1 EK board is used as a reference, and the software support is created and tested for this board. The SAMA5D2 SoC supports ISC, but to have it up and running, please check your board schematics.

Connect the sensor to ISC

Hardware connection

Note that the connector on SAMA5D27 SOM1 EK is different from the one on SAMA5D2 Xplained. Different wiring/extension board are required .
SAMA5D2 Xplained includes an image sensor connector:

It uses two peripherals from SAMA5D2:

• ISC: The DVP interface consists of:
  • Pixel Clock (VSYNC).
  • Horizontal Sync (HSYNC).
  • Vertical Sync (VSYNC).
  • 8 to 12-bits parallel data interface
• TWI: an I2C interface to control the sensor's behavior.
  • And reset and power down control of the sensor.

Connection specification in driver

The ISC driver uses the device tree to specify the ISC and sensor device, please refer to the binding document atmel-isc.txt.
The binding document explains:

• How the DVP interface of the sensor is connected to SAMA5D2.
• How the sensor's I2C control channel is connected to SAMA5D2.
  • We should specify the sensor device under the I2C bus as a child node. (for example, the ov7670 must be connected under I2C1 on SAMA5D2 Xplained)
  • At the same time, we need to specify the pins to control the sensor's reset and power down. (for example, PB11 as reset, PB12 as power down on SAMA5D2 Xplained).
  • Pay attention to the conflicts with GPIOs. The Device Tree needs to disable the conflicting nodes.

     reset-gpios = <&pioA 43 GPIO_ACTIVE_LOW>;
     powerdown-gpios = <&pioA 44 GPIO_ACTIVE_HIGH>;
     

Note that the hardware connections are highly dependent on your board. Check your board schematics to see how the wiring is done.

Starting with Linux Kernel 4.14 (included in Linux4SAM 6.0) and U-boot 2018.07 , we offer the Device Tree support for the ISC and sensors as an Overlay for SAMA5D2 Xplained. Overlays are required for extension boards, like camera sensors in our case. For more information, visit the DT-overlays page.
The DT-overlay for the ISC and for the sensors can be consulted in our Github repository.
Here are links to the overlays themselves, for the SAMA5D2 Xplained board:

• ISC overlay
• OV7670 overlay
• OV7740 overlay

Starting with Linux Kernel 4.19 (included in Linux4SAM 6.1) we offer additional support for omnivision ov5640 for SAMA5D2 Xplained but also for SAMA5D27 SOM1 EK. Here are links to the overlay itself, for the SAMA5D2 Xplained board:

• OV5640 overlay

Here are links to the overlay itself, for the SAMA5D27 SOM1 EK board:

• OV5640 overlay

Starting with Linux4SAM 6.2 we offer support via overlays for all the three sensors (ov7670, ov5640, ov7740) for the SAMA5D27 WLSOM1 EK board.

The boot message

If everything is okay, you can see the log while the system boot-up, it indicates the ov7670 sensor successfully probed.

   ov7670 2-0021: chip found @ 0x42 (AT91)
   

Device file and sysfs

After boot up, you can see a character device file named /dev/video:

   root@sama5d2-xplained:/# ls -l /dev/video0
   crw-rw---- 1 root video 81, 1 Jul 12 11:56 /dev/video0
   

The more information is in the sysfs filesystem.

   root@sama5d2-xplained:/# ls sys/class/video4linux/video0
   dev  dev_debug  device  index  name  power  subsystem  uevent
   root@sama5d2-xplained:/# cat /sys/class/video4linux/video0/name
   atmel_isc
   root@sama5d2-xplained:/# cat /sys/class/video4linux/v4l-subdev0/name
   ov7670 2-0021
   

User space software

Use the v4l-utils

The v4l-utils are a series of packages for handling the video4linux devices.

v4L2-compilance

You can use v4l2-compliance tool to test the v4l2 API compliance of the ISC driver.

# v4l2-compliance
v4l2-compliance SHA: 32cf495ff5da24df54936fae3bf0eb91fba77f3a, 32 bits

Compliance test for atmel_isc deviceatmev/video0:el_isc f0008000.isc: =================  START STATUS  =================
atmel_isc f0008000.isc: Brightness: 0
atmel_isc f0008000.isc: Contrast: 256
atmel_isc f0008000.isc: Gamma: 2


Driver Info:
        Driver name      : atmel_isc
        Card type        : Atmel Image Sensor Controller
        Bus info         : platform:atmel_isc f0008000.isc
        Driver version   : 4.19.16
        Capabilities     : 0x84200001
                Video Capture
                Streaming
                Extended Pix Format
                Device Capabilities
        Device Caps      : 0x04200001
                Video Capture
                Streaming
                Extended Pix Format

Required ioctls:
        test VIDIOC_QUERYCAP: OK

Allow for multiple opens:
        test second /dev/video0 open: OK
        test VIDIOC_QUERYCAP: OK
        test VIDIOC_G/S_PRIORITY: OK
        test for unlimited opens: OK

Debug ioctls:
        test VIDIOC_DBG_G/S_REGISTER: OK (Not Supported)
atmel_isc f0008000.isc: White Balance, Automatic: true
atmel_isc f0008000.isc: ==================  END STATUS  ==================
        test VIDIOC_LOG_STATUS: OK

Input ioctls:
        test VIDIOC_G/S_TUNER/ENUM_FREQ_BANDS: OK (Not Supported)
        test VIDIOC_G/S_FREQUENCY: OK (Not Supported)
        test VIDIOC_S_HW_FREQ_SEEK: OK (Not Supported)
        test VIDIOC_ENUMAUDIO: OK (Not Supported)
        test VIDIOC_G/S/ENUMINPUT: OK
        test VIDIOC_G/S_AUDIO: OK (Not Supported)
        Inputs: 1 Audio Inputs: 0 Tuners: 0

Output ioctls:
        test VIDIOC_G/S_MODULATOR: OK (Not Supported)
        test VIDIOC_G/S_FREQUENCY: OK (Not Supported)
        test VIDIOC_ENUMAUDOUT: OK (Not Supported)
        test VIDIOC_G/S/ENUMOUTPUT: OK (Not Supported)
        test VIDIOC_G/S_AUDOUT: OK (Not Supported)
        Outputs: 0 Audio Outputs: 0 Modulators: 0

Input/Output configuration ioctls:
        test VIDIOC_ENUM/G/S/QUERY_STD: OK (Not Supported)
        test VIDIOC_ENUM/G/S/QUERY_DV_TIMINGS: OK (Not Supported)
        test VIDIOC_DV_TIMINGS_CAP: OK (Not Supported)
        test VIDIOC_G/S_EDID: OK (Not Supported)

Control ioctls (Input 0):
        test VIDIOC_QUERY_EXT_CTRL/QUERYMENU: OK
        test VIDIOC_QUERYCTRL: OK
        test VIDIOC_G/S_CTRL: OK
        test VIDIOC_G/S/TRY_EXT_CTRLS: OK
        test VIDIOC_(UN)SUBSCRIBE_EVENT/DQEVENT: OK
        test VIDIOC_G/S_JPEGCOMP: OK (Not Supported)
        Standard Controls: 6 Private Controls: 0

Format ioctls (Input 0):
        test VIDIOC_ENUM_FMT/FRAMESIZES/FRAMEINTERVALS: OK
        test VIDIOC_G/S_PARM: OK
        test VIDIOC_G_FBUF: OK (Not Supported)
        test VIDIOC_G_FMT: OK
        test VIDIOC_TRY_FMT: OK
        test VIDIOC_S_FMT: OK
        test VIDIOC_G_SLICED_VBI_CAP: OK (Not Supported)
        test Cropping: OK (Not Supported)
        test Composing: OK (Not Supported)
        test Scaling: OK (Not Supported)

Codec ioctls (Input 0):
        test VIDIOC_(TRY_)ENCODER_CMD: OK (Not Supported)
        test VIDIOC_G_ENC_INDEX: OK (Not Supported)
        test VIDIOC_(TRY_)DECODER_CMD: OK (Not Supported)

Buffer ioctls (Input 0):
        test VIDIOC_REQBUFS/CREATE_BUFS/QUERYBUF: OK
        test VIDIOC_EXPBUF: OK
        test Requests: OK (Not Supported)

Total for atmel_isc device /dev/video0: 44, Succeeded: 44, Failed: 0, Warnings: 0

v4l2-ctl

• Display all information available.

# v4l2-ctl --all
Driver Info:
        Driver name      : atmel_isc
        Card type        : Atmel Image Sensor Controller
        Bus info         : platform:atmel_isc f0008000.isc
        Driver version   : 4.19.16
        Capabilities     : 0x84200001
                Video Capture
                Streaming
                Extended Pix Format
                Device Capabilities
        Device Caps      : 0x04200001
                Video Capture
                Streaming
                Extended Pix Format
Priority: 2
Video input : 0 (Camera: ok)
Format Video Capture:
        Width/Height      : 640/480
        Pixel Format      : 'BA81' (8-bit Bayer BGBG/GRGR)
        Field             : None
        Bytes per Line    : 1280
        Size Image        : 614400
        Colorspace        : sRGB
        Transfer Function : Default (maps to sRGB)
        YCbCr/HSV Encoding: Default (maps to ITU-R 601)
        Quantization      : Default (maps to Full Range)
        Flags             :
Streaming Parameters Video Capture:
        Capabilities     : timeperframe
        Frames per second: 24.000 (24/1)
        Read buffers     : 0

User Controls

                     brightness 0x00980900 (int)    : min=-1024 max=1023 step=1 default=0 value=0 flags=slider
                       contrast 0x00980901 (int)    : min=-2048 max=2047 step=1 default=256 value=256 flags=slider
        white_balance_automatic 0x0098090c (bool)   : default=1 value=1
               do_white_balance 0x0098090d (button) : flags=inactive, write-only, execute-on-write
                          gamma 0x00980910 (int)    : min=0 max=2 step=1 default=2 value=2 flags=slider

• Disaplay supported video formats.

# v4l2-ctl --list-formats
ioctl: VIDIOC_ENUM_FMT
        Type: Video Capture

        [0]: 'AR12' (16-bit ARGB 4-4-4-4)
        [1]: 'AR15' (16-bit ARGB 1-5-5-5)
        [2]: 'RGBP' (16-bit RGB 5-6-5)
        [3]: 'AR24' (32-bit BGRA 8-8-8-8)
        [4]: 'XR24' (32-bit BGRX 8-8-8-8)
        [5]: 'YU12' (Planar YUV 4:2:0)
        [6]: 'YUYV' (YUYV 4:2:2)
        [7]: '422P' (Planar YUV 4:2:2)
        [8]: 'GREY' (8-bit Greyscale)
        [9]: 'BA81' (8-bit Bayer BGBG/GRGR)

• Display all controls and their values

# v4l2-ctl --list-ctrls

User Controls

                     brightness 0x00980900 (int)    : min=-1024 max=1023 step=1 default=0 value=0 flags=slider
                       contrast 0x00980901 (int)    : min=-2048 max=2047 step=1 default=256 value=256 flags=slider
        white_balance_automatic 0x0098090c (bool)   : default=1 value=1
               do_white_balance 0x0098090d (button) : flags=inactive, write-only, execute-on-write
                          gamma 0x00980910 (int)    : min=0 max=2 step=1 default=2 value=2 flags=slider

• Get / Set the value of the controls

root@sama5d2-xplained:/# v4l2-ctl --get-ctrl=contrast
contrast: 256
root@sama5d2-xplained:/# v4l2-ctl --set-ctrl=contrast=200
root@sama5d2-xplained:/# v4l2-ctl --get-ctrl=contrast
contrast: 200

Other applications

The user space application for ISC is quite similar to ISI, we just include it from UsingISI page.

fswebcam

fswebcam is a neat and simple webcam app. It captures images from a V4L1/V4L2 compatible device or file, averages them to reduce noise and draws a caption using the GD Graphics Library which also handles compressing the image to PNG or JPEG. The resulting image is saved to a file or sent to stdio where it can be piped to something like ncftpput or scp.

• Add fswebcam in Buildroot
  • Select "Package Selection for the target -> Graphic libraries and applications -> fswebcam".
• Use fswebcam to capture a image.

  #!/bin/sh
  
  VIDEO_DEV=/dev/video0
  SKIP_FRAMES=20
  
  # test preview channel
  fswebcam -S ${SKIP_FRAMES} -d ${VIDEO_DEV} -p RGB565 -r 640x480 rgb565.jpg
  fswebcam -S ${SKIP_FRAMES} -d ${VIDEO_DEV} -p RGB565 -r 320x240 rgb565_defactor.jpg
  
  # test codec channel
  fswebcam -S ${SKIP_FRAMES} -d ${VIDEO_DEV} -p YUYV -r 640x480 yuyv.jpg
  fswebcam -S ${SKIP_FRAMES} -d ${VIDEO_DEV} -p YUYV -r 800x600 yuyv_800x600.jpg
  
  fswebcam -S ${SKIP_FRAMES} -d ${VIDEO_DEV} -p UYVY -r 640x480 uyvy.jpg
  fswebcam -S ${SKIP_FRAMES} -d ${VIDEO_DEV} -p UYVY -r 800x600 uyvy_800x600.jpg
  
  # test codec channel, without any processing, GREY, or Bayer RGB.
  fswebcam -S ${SKIP_FRAMES} -d ${VIDEO_DEV} -p BAYER -r 640x480 bayer_bggr8.jpg
  fswebcam -S ${SKIP_FRAMES} -d ${VIDEO_DEV} -p SGRBG8 -r 640x480 bayer_grbg8.jpg
  
     

  • -S: frames that need to skip.
  • -d /dev/video0: specify the ISI as the input source.
  • -p: pixel format, can be RGB565, YUYV, UYVY, BAYER, SGRBGB8 and etc.
  • -r: resolution.

FFmpeg

FFmpeg is a complete, cross-platform solution to record, convert and stream audio and video. It supports video4linux2 in Linux.

• Add FFmpeg in Buildroot (It's already included in the Linux4SAM buildroot demo).
  • Select "Package Selection for the target -> Audio and video applications -> ffmpeg".
• Use FFmpeg to capture a mpeg4 video clip.

     ffmpeg -r 25 -s vga -t 20 -pix_fmt yuyv422 -f video4linux2 -i /dev/video0 video.avi
     

  • -r: frame rate
  • -s: resolution, it can be qcif, cif, qvga, vga, svga, xga, uxga.
  • -t: time duration in second.
  • -pix_fmt: pixel format, only support yuyv422.
  • -f video4linux2: specify the format. Use ffmpeg -formats will show all supported formats.
  • -i /dev/video0: specify the ISI as the input source. Run following command to check the source name:

    # cat /sys/class/video4linux/video0/name
    isi-camera
             

  • video.avi: output video file name

Tips: As no vcodec specified, it use mpeg4 as default.

Tips: Run ffmpeg -pix_fmts can show all the supported pixel formats.

• Use FFmpeg application to capture images.

     ffmpeg -f video4linux2 -r 1 -s vga -t 4 -i /dev/video0 -pix_fmt yuyv422 -f image2 -vcodec png image%d.png
     

  • -r: frame rate
  • -s: resolution, it can be qcif, cif, qvga, vga, svga, xga, uxga.
  • -t: time duration in second.
  • -i /dev/video0: specify the ISI as the input source. Run following command to check the source name:

    # cat /sys/class/video4linux/video0/name
    isi-camera
             

  • -pix_fmt: pixel format, only support yuyv422.
  • -f image2: image2 sequence format. Use ffmpeg -formats will show all supported formats.
  • -vcodec png: specify output format is png. Use ffmpeg -codecs will show all supported codec.
  • image%d.png: output file name is image1.png, image2.png and etc.

GStreamer

GStreamer is a library for constructing graphs of media-handling components. The applications it supports range from simple Ogg/Vorbis playback, audio/video streaming to complex audio (mixing) and video (non-linear editing) processing.

GStreamer has been ported to a wide range of operating systems, processors and compilers.

• Add GStreamer in Buildroot (It's already included in the Linux4SAM Buildroot demo).
  • Select "Package Selection for the target -> Audio and video applications -> gstreamer" and the plugins that you needed.
• Use GStreamer to preview on LCD.

     # gstreamer 0.10
     gst-launch v4l2src device="/dev/video1" ! video/x-raw-yuv,width=640,height=480 ! ffmpegcolorspace ! fbdevsink
     # gstreamer 1.0
     gst-launch-1.0 v4l2src device="/dev/video1" ! video/x-raw,width=640,height=480 ! videoconvert ! fbdevsink
     

  • v4l2src: a plugin to support v4l2 device as a source
    • device="/dev/video1": specify the ISI as the v4l2 input device.
      • You can check the device name by run command: cat /sys/class/video4linux/video1/name
    • video/x-raw-yuv,width=640,height=480: For gstreamer 0.10, specify the v4l2 output video format and size.
    • video/x-raw,width=640,height=480: For gstreamer 1.0, specify the v4l2 output video format and size.
  • ffmpegcolorspace or videoconvert: a plugin to convert from one color space to another
  • fbdevsink: a plugin to render to framebuffer device

Tips: gstreamer 1.0 is different from 0.10, more detail can check: http://cgit.freedesktop.org/gstreamer/gstreamer/plain/docs/random/porting-to-1.0.txt

Tips: run gst-inspect will show all installed plugins.

Tips: run gst-inspect [plugin name] will show all supported parameters for this plugins.

• 

ZXing barcode reader

ZXing is an open-source, multi-format 1D/2D barcode image processing library implemented in Java, with ports to other languages. The project also includes a barcode reader example.

• Add the ZXing barcode reader application in Buildroot.
  • Add ZXing libary in Buildroot (The Linux4SAM buildroot demo already include it).
    • Select "Package Selection for the target -> Libraries -> Graphics -> zxing".
  • Apply attached patch on top of the buildroot-2012.11.1-at91.
    • This patch will change the zxing project's Makefile to generate not only zxing library but also the barcode reader example.
  • Run command make zxing to generate the barcode application: zxing_barcode.
    • zxing_barcode is located on outpout/target/use/bin/.

• Read barcode from the image by using ZXing barcode reader.
  • Get an picture which include a barcode.
    • Please refer to FFmpeg section for the image capture.
  • Run following command to reader the barcode.

    zxing_barcode *.jpg