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592 lines
22 KiB
592 lines
22 KiB
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SN9C1xx PC Camera Controllers
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Driver for Linux
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=============================
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- Documentation -
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Index
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=====
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1. Copyright
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2. Disclaimer
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3. License
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4. Overview and features
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5. Module dependencies
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6. Module loading
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7. Module parameters
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8. Optional device control through "sysfs"
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9. Supported devices
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10. Notes for V4L2 application developers
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11. Video frame formats
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12. Contact information
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13. Credits
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1. Copyright
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============
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Copyright (C) 2004-2007 by Luca Risolia <luca.risolia@studio.unibo.it>
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2. Disclaimer
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=============
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SONiX is a trademark of SONiX Technology Company Limited, inc.
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This software is not sponsored or developed by SONiX.
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3. License
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==========
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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4. Overview and features
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========================
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This driver attempts to support the video interface of the devices assembling
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the SONiX SN9C101, SN9C102, SN9C103, SN9C105 and SN9C120 PC Camera Controllers
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("SN9C1xx" from now on).
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The driver relies on the Video4Linux2 and USB core modules. It has been
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designed to run properly on SMP systems as well.
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The latest version of the SN9C1xx driver can be found at the following URL:
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http://www.linux-projects.org/
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Some of the features of the driver are:
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- full compliance with the Video4Linux2 API (see also "Notes for V4L2
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application developers" paragraph);
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- available mmap or read/poll methods for video streaming through isochronous
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data transfers;
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- automatic detection of image sensor;
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- support for built-in microphone interface;
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- support for any window resolutions and optional panning within the maximum
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pixel area of image sensor;
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- image downscaling with arbitrary scaling factors from 1, 2 and 4 in both
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directions (see "Notes for V4L2 application developers" paragraph);
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- two different video formats for uncompressed or compressed data in low or
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high compression quality (see also "Notes for V4L2 application developers"
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and "Video frame formats" paragraphs);
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- full support for the capabilities of many of the possible image sensors that
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can be connected to the SN9C1xx bridges, including, for instance, red, green,
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blue and global gain adjustments and exposure (see "Supported devices"
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paragraph for details);
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- use of default color settings for sunlight conditions;
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- dynamic I/O interface for both SN9C1xx and image sensor control and
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monitoring (see "Optional device control through 'sysfs'" paragraph);
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- dynamic driver control thanks to various module parameters (see "Module
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parameters" paragraph);
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- up to 64 cameras can be handled at the same time; they can be connected and
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disconnected from the host many times without turning off the computer, if
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the system supports hotplugging;
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- no known bugs.
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5. Module dependencies
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======================
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For it to work properly, the driver needs kernel support for Video4Linux and
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USB.
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The following options of the kernel configuration file must be enabled and
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corresponding modules must be compiled:
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# Multimedia devices
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#
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CONFIG_VIDEO_DEV=m
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To enable advanced debugging functionality on the device through /sysfs:
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# Multimedia devices
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#
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CONFIG_VIDEO_ADV_DEBUG=y
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# USB support
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#
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CONFIG_USB=m
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In addition, depending on the hardware being used, the modules below are
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necessary:
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# USB Host Controller Drivers
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#
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CONFIG_USB_EHCI_HCD=m
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CONFIG_USB_UHCI_HCD=m
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CONFIG_USB_OHCI_HCD=m
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The SN9C103, SN9c105 and SN9C120 controllers also provide a built-in microphone
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interface. It is supported by the USB Audio driver thanks to the ALSA API:
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# Sound
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#
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CONFIG_SOUND=y
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# Advanced Linux Sound Architecture
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#
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CONFIG_SND=m
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# USB devices
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#
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CONFIG_SND_USB_AUDIO=m
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And finally:
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# USB Multimedia devices
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#
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CONFIG_USB_SN9C102=m
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6. Module loading
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=================
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To use the driver, it is necessary to load the "sn9c102" module into memory
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after every other module required: "videodev", "v4l2_common", "compat_ioctl32",
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"usbcore" and, depending on the USB host controller you have, "ehci-hcd",
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"uhci-hcd" or "ohci-hcd".
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Loading can be done as shown below:
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[root@localhost home]# modprobe sn9c102
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Note that the module is called "sn9c102" for historic reasons, although it
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does not just support the SN9C102.
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At this point all the devices supported by the driver and connected to the USB
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ports should be recognized. You can invoke "dmesg" to analyze kernel messages
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and verify that the loading process has gone well:
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[user@localhost home]$ dmesg
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or, to isolate all the kernel messages generated by the driver:
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[user@localhost home]$ dmesg | grep sn9c102
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7. Module parameters
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====================
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Module parameters are listed below:
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-------------------------------------------------------------------------------
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Name: video_nr
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Type: short array (min = 0, max = 64)
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Syntax: <-1|n[,...]>
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Description: Specify V4L2 minor mode number:
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-1 = use next available
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n = use minor number n
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You can specify up to 64 cameras this way.
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For example:
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video_nr=-1,2,-1 would assign minor number 2 to the second
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recognized camera and use auto for the first one and for every
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other camera.
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Default: -1
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-------------------------------------------------------------------------------
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Name: force_munmap
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Type: bool array (min = 0, max = 64)
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Syntax: <0|1[,...]>
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Description: Force the application to unmap previously mapped buffer memory
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before calling any VIDIOC_S_CROP or VIDIOC_S_FMT ioctl's. Not
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all the applications support this feature. This parameter is
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specific for each detected camera.
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0 = do not force memory unmapping
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1 = force memory unmapping (save memory)
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Default: 0
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-------------------------------------------------------------------------------
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Name: frame_timeout
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Type: uint array (min = 0, max = 64)
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Syntax: <0|n[,...]>
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Description: Timeout for a video frame in seconds before returning an I/O
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error; 0 for infinity. This parameter is specific for each
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detected camera and can be changed at runtime thanks to the
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/sys filesystem interface.
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Default: 2
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-------------------------------------------------------------------------------
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Name: debug
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Type: ushort
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Syntax: <n>
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Description: Debugging information level, from 0 to 3:
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0 = none (use carefully)
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1 = critical errors
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2 = significant informations
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3 = more verbose messages
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Level 3 is useful for testing only. It also shows some more
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informations about the hardware being detected.
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This parameter can be changed at runtime thanks to the /sys
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filesystem interface.
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Default: 2
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-------------------------------------------------------------------------------
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8. Optional device control through "sysfs" [1]
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==========================================
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If the kernel has been compiled with the CONFIG_VIDEO_ADV_DEBUG option enabled,
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it is possible to read and write both the SN9C1xx and the image sensor
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registers by using the "sysfs" filesystem interface.
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Every time a supported device is recognized, a write-only file named "green" is
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created in the /sys/class/video4linux/videoX directory. You can set the green
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channel's gain by writing the desired value to it. The value may range from 0
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to 15 for the SN9C101 or SN9C102 bridges, from 0 to 127 for the SN9C103,
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SN9C105 and SN9C120 bridges.
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Similarly, only for the SN9C103, SN9C105 and SN9C120 controllers, blue and red
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gain control files are available in the same directory, for which accepted
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values may range from 0 to 127.
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There are other four entries in the directory above for each registered camera:
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"reg", "val", "i2c_reg" and "i2c_val". The first two files control the
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SN9C1xx bridge, while the other two control the sensor chip. "reg" and
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"i2c_reg" hold the values of the current register index where the following
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reading/writing operations are addressed at through "val" and "i2c_val". Their
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use is not intended for end-users. Note that "i2c_reg" and "i2c_val" will not
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be created if the sensor does not actually support the standard I2C protocol or
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its registers are not 8-bit long. Also, remember that you must be logged in as
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root before writing to them.
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As an example, suppose we were to want to read the value contained in the
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register number 1 of the sensor register table - which is usually the product
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identifier - of the camera registered as "/dev/video0":
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[root@localhost #] cd /sys/class/video4linux/video0
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[root@localhost #] echo 1 > i2c_reg
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[root@localhost #] cat i2c_val
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Note that "cat" will fail if sensor registers cannot be read.
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Now let's set the green gain's register of the SN9C101 or SN9C102 chips to 2:
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[root@localhost #] echo 0x11 > reg
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[root@localhost #] echo 2 > val
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Note that the SN9C1xx always returns 0 when some of its registers are read.
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To avoid race conditions, all the I/O accesses to the above files are
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serialized.
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The sysfs interface also provides the "frame_header" entry, which exports the
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frame header of the most recent requested and captured video frame. The header
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is always 18-bytes long and is appended to every video frame by the SN9C1xx
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controllers. As an example, this additional information can be used by the user
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application for implementing auto-exposure features via software.
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The following table describes the frame header exported by the SN9C101 and
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SN9C102:
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Byte # Value or bits Description
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------ ------------- -----------
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0x00 0xFF Frame synchronisation pattern
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0x01 0xFF Frame synchronisation pattern
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0x02 0x00 Frame synchronisation pattern
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0x03 0xC4 Frame synchronisation pattern
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0x04 0xC4 Frame synchronisation pattern
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0x05 0x96 Frame synchronisation pattern
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0x06 [3:0] Read channel gain control = (1+R_GAIN/8)
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[7:4] Blue channel gain control = (1+B_GAIN/8)
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0x07 [ 0 ] Compression mode. 0=No compression, 1=Compression enabled
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[2:1] Maximum scale factor for compression
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[ 3 ] 1 = USB fifo(2K bytes) is full
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[ 4 ] 1 = Digital gain is finish
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[ 5 ] 1 = Exposure is finish
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[7:6] Frame index
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0x08 [7:0] Y sum inside Auto-Exposure area (low-byte)
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0x09 [7:0] Y sum inside Auto-Exposure area (high-byte)
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where Y sum = (R/4 + 5G/16 + B/8) / 32
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0x0A [7:0] Y sum outside Auto-Exposure area (low-byte)
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0x0B [7:0] Y sum outside Auto-Exposure area (high-byte)
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where Y sum = (R/4 + 5G/16 + B/8) / 128
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0x0C 0xXX Not used
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0x0D 0xXX Not used
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0x0E 0xXX Not used
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0x0F 0xXX Not used
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0x10 0xXX Not used
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0x11 0xXX Not used
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The following table describes the frame header exported by the SN9C103:
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Byte # Value or bits Description
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------ ------------- -----------
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0x00 0xFF Frame synchronisation pattern
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0x01 0xFF Frame synchronisation pattern
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0x02 0x00 Frame synchronisation pattern
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0x03 0xC4 Frame synchronisation pattern
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0x04 0xC4 Frame synchronisation pattern
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0x05 0x96 Frame synchronisation pattern
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0x06 [6:0] Read channel gain control = (1/2+R_GAIN/64)
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0x07 [6:0] Blue channel gain control = (1/2+B_GAIN/64)
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[7:4]
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0x08 [ 0 ] Compression mode. 0=No compression, 1=Compression enabled
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[2:1] Maximum scale factor for compression
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[ 3 ] 1 = USB fifo(2K bytes) is full
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[ 4 ] 1 = Digital gain is finish
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[ 5 ] 1 = Exposure is finish
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[7:6] Frame index
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0x09 [7:0] Y sum inside Auto-Exposure area (low-byte)
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0x0A [7:0] Y sum inside Auto-Exposure area (high-byte)
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where Y sum = (R/4 + 5G/16 + B/8) / 32
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0x0B [7:0] Y sum outside Auto-Exposure area (low-byte)
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0x0C [7:0] Y sum outside Auto-Exposure area (high-byte)
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where Y sum = (R/4 + 5G/16 + B/8) / 128
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0x0D [1:0] Audio frame number
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[ 2 ] 1 = Audio is recording
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0x0E [7:0] Audio summation (low-byte)
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0x0F [7:0] Audio summation (high-byte)
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0x10 [7:0] Audio sample count
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0x11 [7:0] Audio peak data in audio frame
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The AE area (sx, sy, ex, ey) in the active window can be set by programming the
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registers 0x1c, 0x1d, 0x1e and 0x1f of the SN9C1xx controllers, where one unit
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corresponds to 32 pixels.
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[1] The frame headers exported by the SN9C105 and SN9C120 are not described.
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9. Supported devices
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====================
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None of the names of the companies as well as their products will be mentioned
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here. They have never collaborated with the author, so no advertising.
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From the point of view of a driver, what unambiguously identify a device are
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its vendor and product USB identifiers. Below is a list of known identifiers of
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devices assembling the SN9C1xx PC camera controllers:
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Vendor ID Product ID
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--------- ----------
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0x0458 0x7025
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0x045e 0x00f5
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0x045e 0x00f7
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0x0471 0x0327
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0x0471 0x0328
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0x0c45 0x6001
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0x0c45 0x6005
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0x0c45 0x6007
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0x0c45 0x6009
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0x0c45 0x600d
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0x0c45 0x6011
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0x0c45 0x6019
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0x0c45 0x6024
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0x0c45 0x6025
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0x0c45 0x6028
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0x0c45 0x6029
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0x0c45 0x602a
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0x0c45 0x602b
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0x0c45 0x602c
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0x0c45 0x602d
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0x0c45 0x602e
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0x0c45 0x6030
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0x0c45 0x603f
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0x0c45 0x6080
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0x0c45 0x6082
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0x0c45 0x6083
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0x0c45 0x6088
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0x0c45 0x608a
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0x0c45 0x608b
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0x0c45 0x608c
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0x0c45 0x608e
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0x0c45 0x608f
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0x0c45 0x60a0
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0x0c45 0x60a2
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0x0c45 0x60a3
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0x0c45 0x60a8
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0x0c45 0x60aa
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0x0c45 0x60ab
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0x0c45 0x60ac
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0x0c45 0x60ae
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0x0c45 0x60af
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0x0c45 0x60b0
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0x0c45 0x60b2
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0x0c45 0x60b3
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0x0c45 0x60b8
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0x0c45 0x60ba
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0x0c45 0x60bb
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0x0c45 0x60bc
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0x0c45 0x60be
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0x0c45 0x60c0
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0x0c45 0x60c2
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0x0c45 0x60c8
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0x0c45 0x60cc
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0x0c45 0x60ea
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0x0c45 0x60ec
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0x0c45 0x60ef
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0x0c45 0x60fa
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0x0c45 0x60fb
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0x0c45 0x60fc
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0x0c45 0x60fe
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0x0c45 0x6102
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0x0c45 0x6108
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0x0c45 0x610f
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0x0c45 0x6130
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0x0c45 0x6138
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0x0c45 0x613a
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0x0c45 0x613b
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0x0c45 0x613c
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0x0c45 0x613e
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The list above does not imply that all those devices work with this driver: up
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until now only the ones that assemble the following pairs of SN9C1xx bridges
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and image sensors are supported; kernel messages will always tell you whether
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this is the case (see "Module loading" paragraph):
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Image sensor / SN9C1xx bridge | SN9C10[12] SN9C103 SN9C105 SN9C120
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-------------------------------------------------------------------------------
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HV7131D Hynix Semiconductor | Yes No No No
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HV7131R Hynix Semiconductor | No Yes Yes Yes
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MI-0343 Micron Technology | Yes No No No
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MI-0360 Micron Technology | No Yes Yes Yes
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OV7630 OmniVision Technologies | Yes Yes Yes Yes
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OV7660 OmniVision Technologies | No No Yes Yes
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PAS106B PixArt Imaging | Yes No No No
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PAS202B PixArt Imaging | Yes Yes No No
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TAS5110C1B Taiwan Advanced Sensor | Yes No No No
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TAS5110D Taiwan Advanced Sensor | Yes No No No
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TAS5130D1B Taiwan Advanced Sensor | Yes No No No
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"Yes" means that the pair is supported by the driver, while "No" means that the
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pair does not exist or is not supported by the driver.
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Only some of the available control settings of each image sensor are supported
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through the V4L2 interface.
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Donations of new models for further testing and support would be much
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appreciated. Non-available hardware will not be supported by the author of this
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driver.
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10. Notes for V4L2 application developers
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=========================================
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This driver follows the V4L2 API specifications. In particular, it enforces two
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rules:
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- exactly one I/O method, either "mmap" or "read", is associated with each
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file descriptor. Once it is selected, the application must close and reopen the
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device to switch to the other I/O method;
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- although it is not mandatory, previously mapped buffer memory should always
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be unmapped before calling any "VIDIOC_S_CROP" or "VIDIOC_S_FMT" ioctl's.
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The same number of buffers as before will be allocated again to match the size
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of the new video frames, so you have to map the buffers again before any I/O
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attempts on them.
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Consistently with the hardware limits, this driver also supports image
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downscaling with arbitrary scaling factors from 1, 2 and 4 in both directions.
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However, the V4L2 API specifications don't correctly define how the scaling
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factor can be chosen arbitrarily by the "negotiation" of the "source" and
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"target" rectangles. To work around this flaw, we have added the convention
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that, during the negotiation, whenever the "VIDIOC_S_CROP" ioctl is issued, the
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scaling factor is restored to 1.
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This driver supports two different video formats: the first one is the "8-bit
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Sequential Bayer" format and can be used to obtain uncompressed video data
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from the device through the current I/O method, while the second one provides
|
|
either "raw" compressed video data (without frame headers not related to the
|
|
compressed data) or standard JPEG (with frame headers). The compression quality
|
|
may vary from 0 to 1 and can be selected or queried thanks to the
|
|
VIDIOC_S_JPEGCOMP and VIDIOC_G_JPEGCOMP V4L2 ioctl's. For maximum flexibility,
|
|
both the default active video format and the default compression quality
|
|
depend on how the image sensor being used is initialized.
|
|
|
|
|
|
11. Video frame formats [1]
|
|
=======================
|
|
The SN9C1xx PC Camera Controllers can send images in two possible video
|
|
formats over the USB: either native "Sequential RGB Bayer" or compressed.
|
|
The compression is used to achieve high frame rates. With regard to the
|
|
SN9C101, SN9C102 and SN9C103, the compression is based on the Huffman encoding
|
|
algorithm described below, while with regard to the SN9C105 and SN9C120 the
|
|
compression is based on the JPEG standard.
|
|
The current video format may be selected or queried from the user application
|
|
by calling the VIDIOC_S_FMT or VIDIOC_G_FMT ioctl's, as described in the V4L2
|
|
API specifications.
|
|
|
|
The name "Sequential Bayer" indicates the organization of the red, green and
|
|
blue pixels in one video frame. Each pixel is associated with a 8-bit long
|
|
value and is disposed in memory according to the pattern shown below:
|
|
|
|
B[0] G[1] B[2] G[3] ... B[m-2] G[m-1]
|
|
G[m] R[m+1] G[m+2] R[m+2] ... G[2m-2] R[2m-1]
|
|
...
|
|
... B[(n-1)(m-2)] G[(n-1)(m-1)]
|
|
... G[n(m-2)] R[n(m-1)]
|
|
|
|
The above matrix also represents the sequential or progressive read-out mode of
|
|
the (n, m) Bayer color filter array used in many CCD or CMOS image sensors.
|
|
|
|
The Huffman compressed video frame consists of a bitstream that encodes for
|
|
every R, G, or B pixel the difference between the value of the pixel itself and
|
|
some reference pixel value. Pixels are organised in the Bayer pattern and the
|
|
Bayer sub-pixels are tracked individually and alternatingly. For example, in
|
|
the first line values for the B and G1 pixels are alternatingly encoded, while
|
|
in the second line values for the G2 and R pixels are alternatingly encoded.
|
|
|
|
The pixel reference value is calculated as follows:
|
|
- the 4 top left pixels are encoded in raw uncompressed 8-bit format;
|
|
- the value in the top two rows is the value of the pixel left of the current
|
|
pixel;
|
|
- the value in the left column is the value of the pixel above the current
|
|
pixel;
|
|
- for all other pixels, the reference value is the average of the value of the
|
|
pixel on the left and the value of the pixel above the current pixel;
|
|
- there is one code in the bitstream that specifies the value of a pixel
|
|
directly (in 4-bit resolution);
|
|
- pixel values need to be clamped inside the range [0..255] for proper
|
|
decoding.
|
|
|
|
The algorithm purely describes the conversion from compressed Bayer code used
|
|
in the SN9C101, SN9C102 and SN9C103 chips to uncompressed Bayer. Additional
|
|
steps are required to convert this to a color image (i.e. a color interpolation
|
|
algorithm).
|
|
|
|
The following Huffman codes have been found:
|
|
0: +0 (relative to reference pixel value)
|
|
100: +4
|
|
101: -4?
|
|
1110xxxx: set absolute value to xxxx.0000
|
|
1101: +11
|
|
1111: -11
|
|
11001: +20
|
|
110000: -20
|
|
110001: ??? - these codes are apparently not used
|
|
|
|
[1] The Huffman compression algorithm has been reverse-engineered and
|
|
documented by Bertrik Sikken.
|
|
|
|
|
|
12. Contact information
|
|
=======================
|
|
The author may be contacted by e-mail at <luca.risolia@studio.unibo.it>.
|
|
|
|
GPG/PGP encrypted e-mail's are accepted. The GPG key ID of the author is
|
|
'FCE635A4'; the public 1024-bit key should be available at any keyserver;
|
|
the fingerprint is: '88E8 F32F 7244 68BA 3958 5D40 99DA 5D2A FCE6 35A4'.
|
|
|
|
|
|
13. Credits
|
|
===========
|
|
Many thanks to following persons for their contribute (listed in alphabetical
|
|
order):
|
|
|
|
- David Anderson for the donation of a webcam;
|
|
- Luca Capello for the donation of a webcam;
|
|
- Philippe Coval for having helped testing the PAS202BCA image sensor;
|
|
- Joao Rodrigo Fuzaro, Joao Limirio, Claudio Filho and Caio Begotti for the
|
|
donation of a webcam;
|
|
- Dennis Heitmann for the donation of a webcam;
|
|
- Jon Hollstrom for the donation of a webcam;
|
|
- Nick McGill for the donation of a webcam;
|
|
- Carlos Eduardo Medaglia Dyonisio, who added the support for the PAS202BCB
|
|
image sensor;
|
|
- Stefano Mozzi, who donated 45 EU;
|
|
- Andrew Pearce for the donation of a webcam;
|
|
- John Pullan for the donation of a webcam;
|
|
- Bertrik Sikken, who reverse-engineered and documented the Huffman compression
|
|
algorithm used in the SN9C101, SN9C102 and SN9C103 controllers and
|
|
implemented the first decoder;
|
|
- Ronny Standke for the donation of a webcam;
|
|
- Mizuno Takafumi for the donation of a webcam;
|
|
- an "anonymous" donator (who didn't want his name to be revealed) for the
|
|
donation of a webcam.
|
|
- an anonymous donator for the donation of four webcams and two boards with ten
|
|
image sensors.
|
|
|