[mythtv-users] v4l - one last try....

[Yan Seiner]

Yan Seiner wrote:

>Since xawtv works, and myth hangs, I've been watching the log files....
>
>Here's what happens when I change a channel (not every time, but often):
>
>xawtv:
>
>Feb  1 06:45:25 tooth kernel: bttv0: timeout: drop=283 irq=18815/18816, 
>risc=09fb8194, bits: HSYNC FDSR
>Feb  1 06:45:25 tooth kernel: bttv0: reset, reinitialize
>Feb  1 06:45:25 tooth kernel: bttv0: PLL can sleep, using XTAL (28636363).
>
>mythtv:
>
>Feb  1 06:41:51 tooth kernel: bttv0: timeout: drop=178 irq=4299/4300, 
>risc=1a73f074, bits: HSYNC OFLOW FDSR
>hang....
>
>For some reason, xawtv picks up on the timeout, whereas myth just hangs 
>waiting for a card that needs to be reset...
>
>xawtv also spits out this error, while myth is silent:
>
>ioctl: VIDIOC_DQBUF(index=0;type=VIDEO_CAPTURE;bytesused=0;flags=0x0 
>[];field=ANY;;timecode.type=0;timecode.flags=0;timecode.frames=0;timecode.seconds=0;timecode.minutes=0;timecode.hours=0;timecode.userbits="";sequence=0;memory=unknown): 
>Input/output error
>
>Myth backend actually does say (some 30 seconds after the timeout)
>
>2006-02-01 06:42:26.254 Couldn't read data from the capture card in 15 
>seconds. Stopping.
>
>Afete which the backend seems to go on as usual, except it will no 
>longer respond to frontends at all for anything.  (this is what leads me 
>to believe it's not in my config; myth should not just keel over if I 
>have the wrong channel.... It's not that I can't watch TV, it's that I 
>have to restart the backend every time I try to change the channel....)
>
>Just as a guess, it seems that myth is ignoring an ioctl return code 
>somewhere in the handling of the video stream....  I'll try to track 
>that down, but c++  ain't exactly my strong suit.
>  
>

A quick look-see at the code - the only place where ioctl return codes 
are ignored is in the Channel::SetFormat function, which, AFAICT, gets 
called every time there is a channel change....

Could one of the developers glance at that and see if that may be the 
cause of what I am seeing?  It may be a few days before I can get back 
on this, and I would have to build a qt devel environment first....

-Yan