path: root/Documentation/video4linux/bttv/PROBLEMS
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authorLinus Torvalds <>2005-04-16 15:20:36 -0700
committerLinus Torvalds <>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/video4linux/bttv/PROBLEMS
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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+- Start capturing by pressing "c" or by selecting it via a menu!
+- Start capturing by pressing "c" or by selecting it via a menu!!!
+- The memory of some S3 cards is not recognized right:
+ First of all, if you are not using XFree-3.2 or newer, upgrade AT LEAST to
+ XFree-3.2A! This solved the problem for most people.
+ Start up X11 like this: "XF86_S3 -probeonly" and write down where the
+ linear frame buffer is.
+ If it is different to the address found by bttv install bttv like this:
+ "insmod bttv vidmem=0xfb0"
+ if the linear frame buffer is at 0xfb000000 (i.e. omit the last 5 zeros!)
+ Some S3 cards even take up 64MB of memory but only report 32MB to the BIOS.
+ If this 64MB area overlaps the IO memory of the Bt848 you also have to
+ remap this. E.g.: insmod bttv vidmem=0xfb0 remap=0xfa0
+ If the video memory is found at the right place and there are no address
+ conflicts but still no picture (or the computer even crashes),
+ try disabling features of your PCI chipset in the BIOS setup.
+ Frank Kapahnke <> also reported that problems
+ with his S3 868 went away when he upgraded to XFree 3.2.
+- I still only get a black picture with my S3 card!
+ Even with XFree-3.2A some people have problems with their S3 cards
+ (mostly with Trio 64 but also with some others)
+ Get the free demo version of Accelerated X from and try
+ bttv with it. bttv seems to work with most S3 cards with Accelerated X.
+ Since I do not know much (better make that almost nothing) about VGA card
+ programming I do not know the reason for this.
+ Looks like XFree does something different when setting up the video memory?
+ Maybe somebody can enlighten me?
+ Would be nice if somebody could get this to work with XFree since
+ Accelerated X costs more than some of the grabber cards ...
+ Better linear frame buffer support for S3 cards will probably be in
+ XFree 4.0.
+- Grabbing is not switched off when changing consoles with XFree.
+ That's because XFree and some AcceleratedX versions do not send unmap
+ events.
+- Some popup windows (e.g. of the window manager) are not refreshed.
+ Disable backing store by starting X with the option "-bs"
+- When using 32 bpp in XFree or 24+8bpp mode in AccelX 3.1 the system
+ can sometimes lock up if you use more than 1 bt848 card at the same time.
+ You will always get pixel errors when e.g. using more than 1 card in full
+ screen mode. Maybe we need something faster than the PCI bus ...
+- Some S3 cards and the Matrox Mystique will produce pixel errors with
+ full resolution in 32-bit mode.
+- Some video cards have problems with Accelerated X 4.1