Same image on both bttv-channels.

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sgn
Posts: 68
Joined: Mon Oct 25, 2004 2:36 pm

Same image on both bttv-channels.

Post by sgn » Tue Mar 27, 2012 6:09 pm

I'm using an LMLBT44 with all eight inputs on Debian Squeeze. Worked just fine on Lenny, but after upgrade I get the same image on both of each video interfaces channels. Anyone?

PacoLM
Posts: 970
Joined: Wed Dec 02, 2009 9:55 pm
Location: Spain

Re: Same image on both bttv-channels.

Post by PacoLM » Wed Mar 28, 2012 4:31 am

Code: Select all

ZM_CAPTURES_PER_FRAME
If you are using cameras attached to a video capture card which forces multiple inputs to share one capture chip, it can sometimes produce images with interlaced frames reversed resulting in poor image quality and a distinctive comb edge appearance. Increasing this setting allows you to force additional image captures before one is selected as the captured frame. This allows the capture hardware to 'settle down' and produce better quality images at the price of lesser capture rates. This option has no effect on (a) network cameras, or (b) where multiple inputs do not share a capture chip. This option addresses a similar problem to the ZM_V4L_MULTI_BUFFER option and you should normally change the value of only one of the options at a time.

Code: Select all

ZM_V4L_MULTI_BUFFER
Performance when using Video 4 Linux devices is usually best if multiple buffers are used allowing the next image to be captured while the previous one is being processed. If you have multiple devices on a card sharing one input that requires switching then this approach can sometimes cause frames from one source to be mixed up with frames from another. Switching this option off prevents multi buffering resulting in slower but more stable image capture. This option is ignored for non-local cameras or if only one input is present on a capture chip. This option addresses a similar problem to the ZM_CAPTURES_PER_FRAME option and you should normally change the value of only one of the options at a time.
Uncheck V4L_MULTI_BUFFER and set CAPTURES_PER_FRAME to 2. Post results.

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sgn
Posts: 68
Joined: Mon Oct 25, 2004 2:36 pm

Re: Same image on both bttv-channels.

Post by sgn » Sat Mar 31, 2012 6:52 pm

That did the trick, thanks. Seems the documentation is flawed, it explicitly states that only one of these options should be changed.

bb99
Posts: 943
Joined: Wed Apr 02, 2008 12:04 am

Re: Same image on both bttv-channels.

Post by bb99 » Wed Apr 04, 2012 12:05 am

you should normally change the value of only one of the options at a time.
Usually changing captures per frame to a value of 2 will fix a very high percentage but as with PacoLM, I suggest both right off to get 100% corrected every time. The idea being: get the user up and running now and later you can figure out which is really the issue; it can be both values.

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