[linux-dvb] HVR-4000 and analogue tv

Darron Broad darron at kewl.org
Wed Sep 24 21:09:42 CEST 2008

In message <8C08530B-BAD7-4E83-B1CA-6AB66EE9F53F at ginandtonic.no>, Anders Semb Hermansen wrote:


>Den 24. sep.. 2008 kl. 19.20 skrev Darron Broad:
>> <snip>
>>> Does this mean that mythtv is doing something weird or maybe just
>>> using the v4l api in a different way which the driver cannot handle?
>> This is feasable. I will take a look if I get the time but this
>> is more than likely to be when I have other reasons to look
>> at mythtv so don't expect an immediate response :-)
>I did some more investigating.
>I thought maybe this had something to do with the tuner, since I got  
>snow. So I enabled debugging for the tuner module (debug=1). What I  
>saw was that when I started watching TV in myth, there was a  
>TUNER_SET_STANDBY after frequency and other things was set. This  
>TUNER_SET_STANDBY did not appear when I was just changing channel (and  
>picture worked).
>So I searched the driver for TUNER_STANDBY and found one which I  
>tried. Here is what I did:
>diff -r e5ca4534b543 linux/drivers/media/video/cx88/cx88-video.c
>--- a/linux/drivers/media/video/cx88/cx88-video.c       Tue Sep 09  
>08:29:56 2008 -0700
>+++ b/linux/drivers/media/video/cx88/cx88-video.c       Wed Sep 24  
>20:35:46 2008 +0200
>@@ -1152,7 +1152,8 @@
>         file->private_data = NULL;
>         kfree(fh);
>-       cx88_call_i2c_clients (dev->core, TUNER_SET_STANDBY, NULL);
>+       printk("Don't set standby mode! TUNER_SET_STANDBY NO SIR!");
>+       //cx88_call_i2c_clients (dev->core, TUNER_SET_STANDBY, NULL);
>         return 0;
>  }
>This fixed it!!
>I don't know what side effects this will have. Or if this is caused by  
>wrong use of v4l by mythtv, or driver not implementing it correctly.  
>Those who know the codebase can maybe answer that and come up with a  
>better permanent solution.

I admit I found your fix interesting. In fact, you can reproduce
this using tvtime and cat.


> tvtime -d /dev/video0 &
> cat /dev/video0

The problem in mythtv appears to be in OpenV4L2DeviceAsInput(void)
where is opens the video device twice although I have no confirmed it.



 // /
{:)==={ Darron Broad <darron at kewl.org>
 \\ \ 

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