Bttv devices (bt848, bt878)

Supported devices

• List of bttv devices supported in the linux kernel

Installation

From Gerd Knorr's "README.bttv" distributed in packages such as motv.

Some hints to get the bttv driver up and running

General hints

1. Make sure if your board is recognized correctly. The bttv driver should print a line like this one (Use the 'dmesg' command to see the kernel messages):

bttv0: model: BT848(Hauppauge old)

If your card isn't autodetected correctly, you have to specify the board type as insmod argument (card=n). You might also have to specify tuner=x and pll=x.

Check the driver documentation for details and a list of supported cards. The standard kernel has the bttv documentation in the Documentation/video4linux/bttv directory.

2. [It's recommended you use a recent kernel.]

3. If you have problems with xawtv, you should open a xterm (or whatever your favorite terminal app is) and start xawtv from there. This way you'll see any error messages xawtv might print on stderr which should help to find the source of the problems.

4. If something broke after an update, have a look at the changelog. It might be mentioned there.

Common problems

?: I have a black screen in overlay mode

!: The driver was not initialized correctly, v4l-conf (or the X-Server) has to configure the bttv driver with the current video mode and framebuffer address first. Check if v4l-conf is installed suid root, it needs root priviliges to do this. You can also start v4l-conf from a terminal and check the messages it prints.

?: I have a blue screen. !: Good, the overlay is working. A blue screen is what you get if the grabber chip has no input signal. You are probably using the wrong video source, pick another. Also happens sometimes if the tuner type is wrong, check the driver configuration.

?: I have a noisy screen and/or can't tune (some) stations. !: Most likely the tuner types is wrong, check the driver configuration. It's no problem to do trial-and-error here.

?: The video is outside the window and spread in thin lines over the screen. I: xawtv / v4l-conf didn't autodetect the color depth for your screen correctly. You can fix that with xawtv's -bpp switch.

?: Only the left part of the window is updated, the right one is updated never / sometimes / only if the window is small. !: Your graphics card and/or motherboard can't deal with the data rate going over the PCI bus, leading to canceled PCI transfers. Reduce the color depth, with 16 bpp instead of 32 bpp should work much better.

Hardware specific problems

• bttv + DRI seem not to play nicely together with some cards (ATI Rage128). The linux box just freezes. Don't know why. Suspect it's either a hardware problem or a bug somewhere in DRI (either kernel or xfree86). The only workaround I know of is to turn off DRI.

* Some motherboard chipsets have PCI bugs, especially with PCI-PCI transfers which are used for video overlay.  The bt848/878 chips have some bug compatibility options, which can be enabled to workaround these problems. Have a look at the triton1 and vsfx insmod options. For some known-buggy chipsets these are enabled automagically.

• Sometimes IRQ sharing causes trouble. It works most of the time, but in combination with some hardware and/or drivers it doesn't work. Especially graphic cards are known to cause trouble due to the lack of a IRQ handler. Try disabling the VGA IRQ in the BIOS. Try moving cards to another PCI slot. Your motherboard manual should tell you which PCI slots share IRQ's.