2             SN9C1xx PC Camera Controllers
3                Driver for Linux
4             =============================
6                   - Documentation -
111. Copyright
122. Disclaimer
133. License
144. Overview and features
155. Module dependencies
166. Module loading
177. Module parameters
188. Optional device control through "sysfs"
199. Supported devices
2010. Notes for V4L2 application developers
2111. Video frame formats
2212. Contact information
2313. Credits
261. Copyright
28Copyright (C) 2004-2007 by Luca Risolia <>
312. Disclaimer
33SONiX is a trademark of SONiX Technology Company Limited, inc.
34This software is not sponsored or developed by SONiX.
373. License
39This program is free software; you can redistribute it and/or modify
40it under the terms of the GNU General Public License as published by
41the Free Software Foundation; either version 2 of the License, or
42(at your option) any later version.
44This program is distributed in the hope that it will be useful,
45but WITHOUT ANY WARRANTY; without even the implied warranty of
47GNU General Public License for more details.
49You should have received a copy of the GNU General Public License
50along with this program; if not, write to the Free Software
51Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
544. Overview and features
56This driver attempts to support the video interface of the devices assembling
57the SONiX SN9C101, SN9C102, SN9C103, SN9C105 and SN9C120 PC Camera Controllers
58("SN9C1xx" from now on).
60The driver relies on the Video4Linux2 and USB core modules. It has been
61designed to run properly on SMP systems as well.
63The latest version of the SN9C1xx driver can be found at the following URL:
66Some of the features of the driver are:
68- full compliance with the Video4Linux2 API (see also "Notes for V4L2
69  application developers" paragraph);
70- available mmap or read/poll methods for video streaming through isochronous
71  data transfers;
72- automatic detection of image sensor;
73- support for built-in microphone interface;
74- support for any window resolutions and optional panning within the maximum
75  pixel area of image sensor;
76- image downscaling with arbitrary scaling factors from 1, 2 and 4 in both
77  directions (see "Notes for V4L2 application developers" paragraph);
78- two different video formats for uncompressed or compressed data in low or
79  high compression quality (see also "Notes for V4L2 application developers"
80  and "Video frame formats" paragraphs);
81- full support for the capabilities of many of the possible image sensors that
82  can be connected to the SN9C1xx bridges, including, for instance, red, green,
83  blue and global gain adjustments and exposure (see "Supported devices"
84  paragraph for details);
85- use of default color settings for sunlight conditions;
86- dynamic I/O interface for both SN9C1xx and image sensor control and
87  monitoring (see "Optional device control through 'sysfs'" paragraph);
88- dynamic driver control thanks to various module parameters (see "Module
89  parameters" paragraph);
90- up to 64 cameras can be handled at the same time; they can be connected and
91  disconnected from the host many times without turning off the computer, if
92  the system supports hotplugging;
93- no known bugs.
965. Module dependencies
98For it to work properly, the driver needs kernel support for Video4Linux and
101The following options of the kernel configuration file must be enabled and
102corresponding modules must be compiled:
104    # Multimedia devices
105    #
108To enable advanced debugging functionality on the device through /sysfs:
110    # Multimedia devices
111    #
114    # USB support
115    #
116    CONFIG_USB=m
118In addition, depending on the hardware being used, the modules below are
121    # USB Host Controller Drivers
122    #
127The SN9C103, SN9c105 and SN9C120 controllers also provide a built-in microphone
128interface. It is supported by the USB Audio driver thanks to the ALSA API:
130    # Sound
131    #
134    # Advanced Linux Sound Architecture
135    #
136    CONFIG_SND=m
138    # USB devices
139    #
142And finally:
144    # USB Multimedia devices
145    #
146    CONFIG_USB_SN9C102=m
1496. Module loading
151To use the driver, it is necessary to load the "sn9c102" module into memory
152after every other module required: "videodev", "v4l2_common", "compat_ioctl32",
153"usbcore" and, depending on the USB host controller you have, "ehci-hcd",
154"uhci-hcd" or "ohci-hcd".
156Loading can be done as shown below:
158    [root@localhost home]# modprobe sn9c102
160Note that the module is called "sn9c102" for historic reasons, although it
161does not just support the SN9C102.
163At this point all the devices supported by the driver and connected to the USB
164ports should be recognized. You can invoke "dmesg" to analyze kernel messages
165and verify that the loading process has gone well:
167    [user@localhost home]$ dmesg
169or, to isolate all the kernel messages generated by the driver:
171    [user@localhost home]$ dmesg | grep sn9c102
1747. Module parameters
176Module parameters are listed below:
178Name: video_nr
179Type: short array (min = 0, max = 64)
180Syntax: <-1|n[,...]>
181Description: Specify V4L2 minor mode number:
182        -1 = use next available
183         n = use minor number n
184        You can specify up to 64 cameras this way.
185        For example:
186        video_nr=-1,2,-1 would assign minor number 2 to the second
187        recognized camera and use auto for the first one and for every
188        other camera.
189Default: -1
191Name: force_munmap
192Type: bool array (min = 0, max = 64)
193Syntax: <0|1[,...]>
194Description: Force the application to unmap previously mapped buffer memory
195        before calling any VIDIOC_S_CROP or VIDIOC_S_FMT ioctl's. Not
196        all the applications support this feature. This parameter is
197        specific for each detected camera.
198        0 = do not force memory unmapping
199        1 = force memory unmapping (save memory)
200Default: 0
202Name: frame_timeout
203Type: uint array (min = 0, max = 64)
204Syntax: <0|n[,...]>
205Description: Timeout for a video frame in seconds before returning an I/O
206        error; 0 for infinity. This parameter is specific for each
207        detected camera and can be changed at runtime thanks to the
208        /sys filesystem interface.
209Default: 2
211Name: debug
212Type: ushort
213Syntax: <n>
214Description: Debugging information level, from 0 to 3:
215        0 = none (use carefully)
216        1 = critical errors
217        2 = significant information
218        3 = more verbose messages
219        Level 3 is useful for testing only. It also shows some more
220        information about the hardware being detected.
221        This parameter can be changed at runtime thanks to the /sys
222        filesystem interface.
223Default: 2
2278. Optional device control through "sysfs" [1]
229If the kernel has been compiled with the CONFIG_VIDEO_ADV_DEBUG option enabled,
230it is possible to read and write both the SN9C1xx and the image sensor
231registers by using the "sysfs" filesystem interface.
233Every time a supported device is recognized, a write-only file named "green" is
234created in the /sys/class/video4linux/videoX directory. You can set the green
235channel's gain by writing the desired value to it. The value may range from 0
236to 15 for the SN9C101 or SN9C102 bridges, from 0 to 127 for the SN9C103,
237SN9C105 and SN9C120 bridges.
238Similarly, only for the SN9C103, SN9C105 and SN9C120 controllers, blue and red
239gain control files are available in the same directory, for which accepted
240values may range from 0 to 127.
242There are other four entries in the directory above for each registered camera:
243"reg", "val", "i2c_reg" and "i2c_val". The first two files control the
244SN9C1xx bridge, while the other two control the sensor chip. "reg" and
245"i2c_reg" hold the values of the current register index where the following
246reading/writing operations are addressed at through "val" and "i2c_val". Their
247use is not intended for end-users. Note that "i2c_reg" and "i2c_val" will not
248be created if the sensor does not actually support the standard I2C protocol or
249its registers are not 8-bit long. Also, remember that you must be logged in as
250root before writing to them.
252As an example, suppose we were to want to read the value contained in the
253register number 1 of the sensor register table - which is usually the product
254identifier - of the camera registered as "/dev/video0":
256    [root@localhost #] cd /sys/class/video4linux/video0
257    [root@localhost #] echo 1 > i2c_reg
258    [root@localhost #] cat i2c_val
260Note that "cat" will fail if sensor registers cannot be read.
262Now let's set the green gain's register of the SN9C101 or SN9C102 chips to 2:
264    [root@localhost #] echo 0x11 > reg
265    [root@localhost #] echo 2 > val
267Note that the SN9C1xx always returns 0 when some of its registers are read.
268To avoid race conditions, all the I/O accesses to the above files are
270The sysfs interface also provides the "frame_header" entry, which exports the
271frame header of the most recent requested and captured video frame. The header
272is always 18-bytes long and is appended to every video frame by the SN9C1xx
273controllers. As an example, this additional information can be used by the user
274application for implementing auto-exposure features via software.
276The following table describes the frame header exported by the SN9C101 and
279Byte # Value or bits Description
280------ ------------- -----------
2810x00 0xFF Frame synchronisation pattern
2820x01 0xFF Frame synchronisation pattern
2830x02 0x00 Frame synchronisation pattern
2840x03 0xC4 Frame synchronisation pattern
2850x04 0xC4 Frame synchronisation pattern
2860x05 0x96 Frame synchronisation pattern
2870x06 [3:0] Read channel gain control = (1+R_GAIN/8)
288    [7:4] Blue channel gain control = (1+B_GAIN/8)
2890x07 [ 0 ] Compression mode. 0=No compression, 1=Compression enabled
290    [2:1] Maximum scale factor for compression
291    [ 3 ] 1 = USB fifo(2K bytes) is full
292    [ 4 ] 1 = Digital gain is finish
293    [ 5 ] 1 = Exposure is finish
294    [7:6] Frame index
2950x08 [7:0] Y sum inside Auto-Exposure area (low-byte)
2960x09 [7:0] Y sum inside Auto-Exposure area (high-byte)
297              where Y sum = (R/4 + 5G/16 + B/8) / 32
2980x0A [7:0] Y sum outside Auto-Exposure area (low-byte)
2990x0B [7:0] Y sum outside Auto-Exposure area (high-byte)
300              where Y sum = (R/4 + 5G/16 + B/8) / 128
3010x0C 0xXX Not used
3020x0D 0xXX Not used
3030x0E 0xXX Not used
3040x0F 0xXX Not used
3050x10 0xXX Not used
3060x11 0xXX Not used
308The following table describes the frame header exported by the SN9C103:
310Byte # Value or bits Description
311------ ------------- -----------
3120x00 0xFF Frame synchronisation pattern
3130x01 0xFF Frame synchronisation pattern
3140x02 0x00 Frame synchronisation pattern
3150x03 0xC4 Frame synchronisation pattern
3160x04 0xC4 Frame synchronisation pattern
3170x05 0x96 Frame synchronisation pattern
3180x06 [6:0] Read channel gain control = (1/2+R_GAIN/64)
3190x07 [6:0] Blue channel gain control = (1/2+B_GAIN/64)
320    [7:4]
3210x08 [ 0 ] Compression mode. 0=No compression, 1=Compression enabled
322    [2:1] Maximum scale factor for compression
323    [ 3 ] 1 = USB fifo(2K bytes) is full
324    [ 4 ] 1 = Digital gain is finish
325    [ 5 ] 1 = Exposure is finish
326    [7:6] Frame index
3270x09 [7:0] Y sum inside Auto-Exposure area (low-byte)
3280x0A [7:0] Y sum inside Auto-Exposure area (high-byte)
329              where Y sum = (R/4 + 5G/16 + B/8) / 32
3300x0B [7:0] Y sum outside Auto-Exposure area (low-byte)
3310x0C [7:0] Y sum outside Auto-Exposure area (high-byte)
332              where Y sum = (R/4 + 5G/16 + B/8) / 128
3330x0D [1:0] Audio frame number
334    [ 2 ] 1 = Audio is recording
3350x0E [7:0] Audio summation (low-byte)
3360x0F [7:0] Audio summation (high-byte)
3370x10 [7:0] Audio sample count
3380x11 [7:0] Audio peak data in audio frame
340The AE area (sx, sy, ex, ey) in the active window can be set by programming the
341registers 0x1c, 0x1d, 0x1e and 0x1f of the SN9C1xx controllers, where one unit
342corresponds to 32 pixels.
344[1] The frame headers exported by the SN9C105 and SN9C120 are not described.
3479. Supported devices
349None of the names of the companies as well as their products will be mentioned
350here. They have never collaborated with the author, so no advertising.
352From the point of view of a driver, what unambiguously identify a device are
353its vendor and product USB identifiers. Below is a list of known identifiers of
354devices assembling the SN9C1xx PC camera controllers:
356Vendor ID Product ID
357--------- ----------
3580x0458 0x7025
3590x045e 0x00f5
3600x045e 0x00f7
3610x0471 0x0327
3620x0471 0x0328
3630x0c45 0x6001
3640x0c45 0x6005
3650x0c45 0x6007
3660x0c45 0x6009
3670x0c45 0x600d
3680x0c45 0x6011
3690x0c45 0x6019
3700x0c45 0x6024
3710x0c45 0x6025
3720x0c45 0x6028
3730x0c45 0x6029
3740x0c45 0x602a
3750x0c45 0x602b
3760x0c45 0x602c
3770x0c45 0x602d
3780x0c45 0x602e
3790x0c45 0x6030
3800x0c45 0x603f
3810x0c45 0x6080
3820x0c45 0x6082
3830x0c45 0x6083
3840x0c45 0x6088
3850x0c45 0x608a
3860x0c45 0x608b
3870x0c45 0x608c
3880x0c45 0x608e
3890x0c45 0x608f
3900x0c45 0x60a0
3910x0c45 0x60a2
3920x0c45 0x60a3
3930x0c45 0x60a8
3940x0c45 0x60aa
3950x0c45 0x60ab
3960x0c45 0x60ac
3970x0c45 0x60ae
3980x0c45 0x60af
3990x0c45 0x60b0
4000x0c45 0x60b2
4010x0c45 0x60b3
4020x0c45 0x60b8
4030x0c45 0x60ba
4040x0c45 0x60bb
4050x0c45 0x60bc
4060x0c45 0x60be
4070x0c45 0x60c0
4080x0c45 0x60c2
4090x0c45 0x60c8
4100x0c45 0x60cc
4110x0c45 0x60ea
4120x0c45 0x60ec
4130x0c45 0x60ef
4140x0c45 0x60fa
4150x0c45 0x60fb
4160x0c45 0x60fc
4170x0c45 0x60fe
4180x0c45 0x6102
4190x0c45 0x6108
4200x0c45 0x610f
4210x0c45 0x6130
4220x0c45 0x6138
4230x0c45 0x613a
4240x0c45 0x613b
4250x0c45 0x613c
4260x0c45 0x613e
428The list above does not imply that all those devices work with this driver: up
429until now only the ones that assemble the following pairs of SN9C1xx bridges
430and image sensors are supported; kernel messages will always tell you whether
431this is the case (see "Module loading" paragraph):
433Image sensor / SN9C1xx bridge | SN9C10[12] SN9C103 SN9C105 SN9C120
435HV7131D Hynix Semiconductor | Yes No No No
436HV7131R Hynix Semiconductor | No Yes Yes Yes
437MI-0343 Micron Technology | Yes No No No
438MI-0360 Micron Technology | No Yes Yes Yes
439OV7630 OmniVision Technologies | Yes Yes Yes Yes
440OV7660 OmniVision Technologies | No No Yes Yes
441PAS106B PixArt Imaging | Yes No No No
442PAS202B PixArt Imaging | Yes Yes No No
443TAS5110C1B Taiwan Advanced Sensor | Yes No No No
444TAS5110D Taiwan Advanced Sensor | Yes No No No
445TAS5130D1B Taiwan Advanced Sensor | Yes No No No
447"Yes" means that the pair is supported by the driver, while "No" means that the
448pair does not exist or is not supported by the driver.
450Only some of the available control settings of each image sensor are supported
451through the V4L2 interface.
453Donations of new models for further testing and support would be much
454appreciated. Non-available hardware will not be supported by the author of this
45810. Notes for V4L2 application developers
460This driver follows the V4L2 API specifications. In particular, it enforces two
463- exactly one I/O method, either "mmap" or "read", is associated with each
464file descriptor. Once it is selected, the application must close and reopen the
465device to switch to the other I/O method;
467- although it is not mandatory, previously mapped buffer memory should always
468be unmapped before calling any "VIDIOC_S_CROP" or "VIDIOC_S_FMT" ioctl's.
469The same number of buffers as before will be allocated again to match the size
470of the new video frames, so you have to map the buffers again before any I/O
471attempts on them.
473Consistently with the hardware limits, this driver also supports image
474downscaling with arbitrary scaling factors from 1, 2 and 4 in both directions.
475However, the V4L2 API specifications don't correctly define how the scaling
476factor can be chosen arbitrarily by the "negotiation" of the "source" and
477"target" rectangles. To work around this flaw, we have added the convention
478that, during the negotiation, whenever the "VIDIOC_S_CROP" ioctl is issued, the
479scaling factor is restored to 1.
481This driver supports two different video formats: the first one is the "8-bit
482Sequential Bayer" format and can be used to obtain uncompressed video data
483from the device through the current I/O method, while the second one provides
484either "raw" compressed video data (without frame headers not related to the
485compressed data) or standard JPEG (with frame headers). The compression quality
486may vary from 0 to 1 and can be selected or queried thanks to the
487VIDIOC_S_JPEGCOMP and VIDIOC_G_JPEGCOMP V4L2 ioctl's. For maximum flexibility,
488both the default active video format and the default compression quality
489depend on how the image sensor being used is initialized.
49211. Video frame formats [1]
494The SN9C1xx PC Camera Controllers can send images in two possible video
495formats over the USB: either native "Sequential RGB Bayer" or compressed.
496The compression is used to achieve high frame rates. With regard to the
497SN9C101, SN9C102 and SN9C103, the compression is based on the Huffman encoding
498algorithm described below, while with regard to the SN9C105 and SN9C120 the
499compression is based on the JPEG standard.
500The current video format may be selected or queried from the user application
501by calling the VIDIOC_S_FMT or VIDIOC_G_FMT ioctl's, as described in the V4L2
502API specifications.
504The name "Sequential Bayer" indicates the organization of the red, green and
505blue pixels in one video frame. Each pixel is associated with a 8-bit long
506value and is disposed in memory according to the pattern shown below:
508B[0] G[1] B[2] G[3] ... B[m-2] G[m-1]
509G[m] R[m+1] G[m+2] R[m+2] ... G[2m-2] R[2m-1]
511... B[(n-1)(m-2)] G[(n-1)(m-1)]
512... G[n(m-2)] R[n(m-1)]
514The above matrix also represents the sequential or progressive read-out mode of
515the (n, m) Bayer color filter array used in many CCD or CMOS image sensors.
517The Huffman compressed video frame consists of a bitstream that encodes for
518every R, G, or B pixel the difference between the value of the pixel itself and
519some reference pixel value. Pixels are organised in the Bayer pattern and the
520Bayer sub-pixels are tracked individually and alternatingly. For example, in
521the first line values for the B and G1 pixels are alternatingly encoded, while
522in the second line values for the G2 and R pixels are alternatingly encoded.
524The pixel reference value is calculated as follows:
525- the 4 top left pixels are encoded in raw uncompressed 8-bit format;
526- the value in the top two rows is the value of the pixel left of the current
527  pixel;
528- the value in the left column is the value of the pixel above the current
529  pixel;
530- for all other pixels, the reference value is the average of the value of the
531  pixel on the left and the value of the pixel above the current pixel;
532- there is one code in the bitstream that specifies the value of a pixel
533  directly (in 4-bit resolution);
534- pixel values need to be clamped inside the range [0..255] for proper
535  decoding.
537The algorithm purely describes the conversion from compressed Bayer code used
538in the SN9C101, SN9C102 and SN9C103 chips to uncompressed Bayer. Additional
539steps are required to convert this to a color image (i.e. a color interpolation
542The following Huffman codes have been found:
5430: +0 (relative to reference pixel value)
544100: +4
545101: -4?
5461110xxxx: set absolute value to xxxx.0000
5471101: +11
5481111: -11
54911001: +20
550110000: -20
551110001: ??? - these codes are apparently not used
553[1] The Huffman compression algorithm has been reverse-engineered and
554    documented by Bertrik Sikken.
55712. Contact information
559The author may be contacted by e-mail at <>.
561GPG/PGP encrypted e-mail's are accepted. The GPG key ID of the author is
562'FCE635A4'; the public 1024-bit key should be available at any keyserver;
563the fingerprint is: '88E8 F32F 7244 68BA 3958 5D40 99DA 5D2A FCE6 35A4'.
56613. Credits
568Many thanks to following persons for their contribute (listed in alphabetical
571- David Anderson for the donation of a webcam;
572- Luca Capello for the donation of a webcam;
573- Philippe Coval for having helped testing the PAS202BCA image sensor;
574- Joao Rodrigo Fuzaro, Joao Limirio, Claudio Filho and Caio Begotti for the
575  donation of a webcam;
576- Dennis Heitmann for the donation of a webcam;
577- Jon Hollstrom for the donation of a webcam;
578- Nick McGill for the donation of a webcam;
579- Carlos Eduardo Medaglia Dyonisio, who added the support for the PAS202BCB
580  image sensor;
581- Stefano Mozzi, who donated 45 EU;
582- Andrew Pearce for the donation of a webcam;
583- John Pullan for the donation of a webcam;
584- Bertrik Sikken, who reverse-engineered and documented the Huffman compression
585  algorithm used in the SN9C101, SN9C102 and SN9C103 controllers and
586  implemented the first decoder;
587- Ronny Standke for the donation of a webcam;
588- Mizuno Takafumi for the donation of a webcam;
589- an "anonymous" donator (who didn't want his name to be revealed) for the
590  donation of a webcam.
591- an anonymous donator for the donation of four webcams and two boards with ten
592  image sensors.

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