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<html><head><title>FAQ Linux Philips USB webcam drivers</title></head><LINK REL="STYLESHEET" HREF="webcam.css" TYPE="text/css"><body><h1>Troubleshooting, Frequently Asked Questions, Hints & Tips</h1><p>To make life easier for you, I divided the answers into severalsections. Please read this carefully before you send mail. Chances areyour question is already answered in here.</p><h4>General</h4><ol> <li><a href="nda.html">Where's the source?</a> <li><a href="which.html">Which camera should I buy?</a> <li><a href="#8">The box says PCVC675K or PCVC680K... Is this "K" model different?</a> <li><a href="#15">Can you compile a module for me for kernel X or Linux distro Y?</a> <li><a href="#16">Which kernel versions <i>do</i> you support, then?</a> <li><a href="#G17">Which OS/processors/hardware do you support?</a> <li><a href="#Q18">Can you help me with a driver for Novell/OS2/Win CE/MacOS X?</a></li> <li><a href="#18">When will you write support for the microphone?</a> <li><a href="#Q10">Is there a way to access the button on the cam?</a> <li><a href="#Q12">Why are the PCA635, PCVC665 (Vesta Fun) and PCVC720 (ToUCam XS) not supported by your driver?</a> <li><a href="#Q14">Should I always use the do-it-yourself package?</a> <li><a href="#Q15">I want to set an exposure time of 2 minutes for my astronomy observations. Is this possible?</a> <li><a href="#Q16">The driver from kernel >= 2.4.5 doesn't work anymore with tool XYZ.</a> <li><a href="#Q17">I don't have /proc/bus/usb/devices!</a></li></ol><h4>Downloads & Installation</h4><ol> <li><a href="#13">What are the correct device-nodes for the webcam?</a> <li><a href="#14">What device gets the cam assigned when I load the module/plug the camera in? Can I specify the video device?</a> <li><a href="#19">What device gets the microphone assigned?</a> <li><a href="#I5">Where should I install the pwcx.o module? After each kernel upgrade I have to copy it again to /lib/modules.</a> <li><a href="#I6">I have no clue as how to configure my RedHat/Suse/Mandrake/Oompa-Loompa Linux distribution. Why don't you write step-by-step instructions on what I must do?</a></li> <li><a href="#I7">I have trouble using the webcam on an ARM system</a></li></ol><h4>Loading the module</h4><ol> <li><a href="#2">modprobe doesn't recognize the usb modules</a> <li><a href="#3">Loading the module gives me an 'Oops'...</a> <li><a href="#11">Version mismatch on Mandrake (and other) distributions</a> <li><a href="#24">The module loads, USB says something about a device detected, but no go...</a> <li><a href="#L6">I get some USB message about "device not accepting address" when loading the module, and it doesn't work...</a> <li><a href="#L7">PWCX complains about version mismatch</a></li> <li><a href="#L8">Is there a way to automatically load PWCX after the PWC module?</a></li> <li><a href="#L9">Modutils complains that PWCX is 'tainting' the kernel. What's up?</a></li> <li><a href="#L10">PWC(X) won't load because of 'unresolved symbols'</a></li> <li><a href="#L11">PWCX won't load because of 'invalid module format'</a></li></ol><h4>Running applications</h4><ol> <li><a href="#Q3">The box says I can take images at 800x600 and even 1280x960, but I can't seem to set this resolution?</a> <li><a href="#R11">The box says I can take images at 60 frames per second, but I seem to be stuck at 15 fps?!</a> <li><a href="#23">Can I use multiple cameras at the same time?</a> <li><a href="#R9">Everything loads fine, but I just get a black image with all the utilities I tried</a></li> <li><a href="#R1">When I run 'camstream' and I move a window or do something, X crashes</a> <li><a href="#5">There's a short green bar blipping on and off on the right hand side of the screen</a> <li><a href="#6">Dumping frame...</a> <li><a href="#R7">Scratch buffer under/overflow...</a> <li><a href="#20">What applications work with this cam and module?</a> <li><a href="#22">I get lots of buffer underflow/overflows, or mysterious 'URB unlink timeout' messages</a> <li><a href="#25">The image is too dark/bright/discoloured</a> <li><a href="#R10">I only get a very small picture within an enormous black/gray area</a> <li><a href="#R12">My image is mirrored</a></li> <li><a href="#R13">I want to hook up 10 cameras and take high resolution snapshots from them in succession. Is this possible?</a> <li><a href="#R14">What does "interrupt, status 2, frame #####" mean?</a></li> <li><a href="#R15">I have triple vision!</a></li></ol><hr><h2>Answers</h2><h3><a name="1">Where's the source?</a></h3><p>This question is now partially defunct. There used to be a binary onlydriver, and the story is covered <a href="nda.html">here</a>. Now, only asmall binary only part remains; a fully functional driver is includedin the main Linux 2.4.* kernel.</p><h3><a name="2">Modprobe doesn't recognize the usb modules</a></h3><p>Unless you have a very recent version of 'modutils', modprobe won'trecognize the usb modules. The place to download modutils isftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/modutils/v2.3<br>You can place the module in /lib/modules/<i>kernel-version</i>/misc/,or insert the modules manually with insmod.<p>Also, don't forget to run 'depmod -a' once when you just installed themodules.<h3><a name="3">Loading the module gives me an 'Oops'...</a></h3><p>This could be a number of things... First make sure you have the rightkernel and applied all necessary patches and/or source. Second, check yourprocessor version. If the P5 version of a module loads and the P6 versionOopses, then your processor does not understand some of the assemblyinstructions generated by gcc. If your Oops trace contains a line like this:<p><pre>Code: 0f 4d c2 31 ....</pre><p>And the first byte is '0f' you can be reasonably sure that is theproblem. The P6 version has only a little performance gain over the P5version.<p>If the problem persists however, run the 'Oops' message through<b>ksymoops</b> and send the output to me... I may be able to determinesomething from that. Also, tell me following things:<ul> <li>What kind of system you have (processor, uniprocessor or SMP) <li>The type of USB controller (UHCI, OHCI) <li>What other USB modules you have loaded <li>The kernel version <li><b>The module version</b></ul> <h3><a name="R1">When I run 'camstream' and I move a window or do somethingsimilar, X crashes</a></h3><p>Note: this problem seems to have gone away with the 3.3.* versions of XFree86.<p>This is not the fault of my module; rather, X doesn't like to updateits screen 15 times a second, especially with larger images. I suspect it's abuffer overflow problem or something. I hope to solve this by either usingthe X shared memory extension or direct writes to video memory.<h3><a name="5">There's a short green bar blipping on and off on theright hand side of the image</a></h3><p>The 645/646 models sometimes show a short green bar on the right handside of the image. This has been fixed in the 4.* modules.<h3><a name="6">Dumping frame...</a></h3><p>The usb-pwc-*.o module produces a few messages in the kernel log; most ofthem speak for themselves, but you might see this:<dir>linux: usb-pwc: dumping frame XXX.</dir><p>where XXX is a number that jumps up. This is nothing serious; it just meansthat the program that currently reads information from the driver is laggingbehind and that the driver had to dump incoming frames from the camera.After 20 such messages it will stop nagging you, and print a total when thewebcam device is closed.<h3><a name="R7">Scratch buffer under/overflow...</a></h3><p>Some messages that you might see in your kernel log are about scratchbuffer over- or underflow. This is harmless; it means that the driverreceived too much or too little data in one frame and it can't be used todecode an image. The video frame is discarded and the driver waits for a newframe to arrive. This message could appear now and then when the system isloaded heavily or when there's a lot of USB traffic.</p><p>See also the item about <a href="#R14">interrupt, status messages from UHCI/OHCI.</a>.<h3><a name="8">The box says PCVC675K or PCVC680K... Is this"K" model different?</a></h3><p>Nope. It's just a fancy addition to the version number.<h3><a name="11">Version mismatch on Mandrake (and other) distributions</a></h3><p>Some distributions (Mandrake, Redhat, some non-english distro's) areshipped with kernels that will give version mismatches while loadingthe webcam modules.<p>For example, Mandranke kernel have a version number like"2.2.14-15mdk", so insmod/modprobe complains that thekernel-version of the pwc-module is "2.2.14". Often these kernelscontain additional/distro-specific code and the extra version stringindicates this. But it breaks compatibility.<p>You can try forcing the module in with the '-f' option, but do that onlyif you know your kernel version really matches the module. But the best wayis to use a vanilla kernel (see the <a href="install.html">installationnotes</a>).<p>Modules are <b>always</b> compiled on stock Linux kernels.<h3><a name="Q3">The box says I can take images at 800x600 and even1280x960, but I can't seem to set this resolution (with camstream)? InWindows it works...</a></h3><p>You shouldn't always believe what's printed on the box, nor what Windowsdoes :) But seriously:</p><p>The point is that these resolutions are not really possible with thecams: the CCDs (light sensitive sensors) only have a resolution of 352x288(PCVC645/646) or 640x480 (PCA675/680/690/730/740) pixels. This is thephysical limit of the cameras. Any larger pictures are simply enlargedversions of the images at maximum resolution (though you would have to lookreal close to see it). So, rather than giving you the false impression youget some extraordinary imagesize, I limit the driver to the physicalcharacteristics of the cams.</p><p>Below is a table that shows the possible resolutions and framerates forthe webcams. On the left, all physical resolutions are listed; at the top, thevarious framerates.</p><p>If a cell is blank, it means the combination of resolution and framerate isnot supported. A green cell means the combination is supported uncompressed;a red cell indicates that combination is only available in compressed mode.</p><p><table border="1"><tr> <th rowspan="2" valign="bottom">Size</th> <th colspan="8">PCA 645/646 & VC010</th> <th rowspan="8" width="15"> </td> <th colspan="6">PCVC 675/680/690</th> <th rowspan="8" width="15"> </th> <th colspan="6">PCVC 730/740</th></tr><tr> <th width="30">3.75</th> <th width="30">5</th> <th width="30">7.5</th> <th width="30">10</th> <th width="30">12</th> <th width="30">15</th> <th width="30">20</th> <th width="30">24</th> <th width="30">5</th> <th width="30">10</th> <th width="30">15</th> <th width="30">20</th> <th width="30">25</th> <th width="30">30</th> <th width="30">5</th> <th width="30">10</th> <th width="30">15</th> <th width="30">20</th> <th width="30">25</th> <th width="30">30</th></tr> <tr> <th>sQCIF<br>128x96</th> <td> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td> </td> <td> </td> <td> </td> <td> </td> <td> </td> <td> </td></tr><tr> <th>QSIF<br>160x120</th> <td> </td> <td> </td> <td> </td> <td> </td> <td> </td> <td> </td> <td> </td> <td> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td></tr> <tr> <th>QCIF<br>176x144</th> <td> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#00cc00"> </td> <td bgcolor="#cc0000"> </td> <td> </td> <td> </td> <td> </td> <td> </td> <td> </td> <td> </td></tr><tr> <th>SIF<br>320x240</th> <td> </td> <td> </td> <td> </td>⌨️ 快捷键说明
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