Re: Progressive scan with BTTV

["Dhananjai M. Rao" <dmadhava@xxxxxxxxx>]

Hi,

I looked at the data sheet in my lunch break and it seems like the bt878
family is meant to decode interlaced video fields that are compatible with
NTSC/PAL and other formats.  It seems like it does not have hardware mode
for a non-interlaced video.  Maybe one of the HDTV or S-video inputs could 
be used for this purpose but I am not sure.  In addition, your camera/card 
may not have connectors etc.  In any case, I guess at this time you can 
pretty much assume that the bt878 chip is not going to let non-interlaced 
video through.  So if you do put your camera in this non-interlaced 
format, then the images you capture via the V4L API is going to be 
garbled.

However, (I know this is a silly suggestion, but..) would running a
de-interlacing algorithm between successive frames from your V4L device
solve your problem?

thanks

with regards
-DJ

>
> When frame mode is selected, the result is as you would expect, with the
> fields intermixed.
> BTW, I am capturing single frames and writing .pgm files, not viewing TV.
> 
> Thanks,
> David
> 
> on Thu, 9 Dec 2004 Dhananjai M. Rao wrote:
> > Hi,
> > 
> > When you put your camera control section on "non-interlaced" mode and 
> > connect it to a TV set, does your TV set show video properly or any video 
> > at all?
> > 
> > thanks
> > 
> > with regards
> > -DJ
> > 
> > 
> >>Thank you for your replies.
> >>
> >>My camera has control selection for field (standard interlaced mode) or 
> >>frame (non-interlaced, or progressive scan mode). Everything worked fine 
> >>in field mode, but I need frame mode for my machine vision project.
> >>
> >>For my prototype, I'm using one of the many bt878A cards available - 
> >>perhaps it won't work for me. Would be a pity since the bttv driver is 
> >>so mature, and the bt878 series chips are widely available.
> >>
> >>I have read the Conexant data sheet - all 200 or so pages - but could 
> >>find nothing conclusive.
> >>
> >>The bttv driver author, Gerd Knorr, sometimes replies to this list.  I 
> >>emailed him off-list, but not sure he received my email - his ISP had my 
> >>office email server blacklisted (WHY? don't know).  Gerd - are you out 
> >>there?
> >>
> >>on Thu, 9 Dec 2004 Dhananjai M. Rao wrote:
> >>
> >>>Hi,
> >>>
> >>>When you use BTTV without progressive scan, do you get any output at all?  
> >>>Maybe your video card does not work with the progressive scan mode?  If
> >>>your card uses one of the bt878 chips, then you could look up the
> >>>data sheet for the chip (off conexant website at:  
> >>>http://www.conexant.com/servlets/DownloadServlet/100600B.pdf?FileId=443)  
> >>>and possibly the data sheet gives some tips on how to read and process
> >>>progressive scan off this chip.  I looked very briefly at the data sheet 
> >>>and there was no mention of progressive scan stuff.  I did see references 
> >>>to interlaced video tho'
> >>>
> >>>On the flip side, can you connect your camera to a standard TV's 
> >>>composite input and get proper video?  If so, then your capture card 
> >>>should be doing the same thing that your TV is doing.  Maybe if you 
> >>>provide some more details others can try to help you a bit further with 
> >>>your efforts.  
> >>>
> >>>In addition, I am not sure if the bttv driver developers hang around this
> >>>mailing list.  Do you any of you know if the bttv driver developers 
> >>>participate in this mailing list?
> >>>
> >>>thanks
> >>>
> >>>with regards
> >>>-DJ
> >>>
> >>>
> >>>
> <--snip-->
> 
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