[linux-dvb] Re: HDTV & DVB / VDR (dscaler ..)

[<mocm@convergence.de>]

Emil Naepflein writes:
 > Does the MPEG stream transmitted bei DVB contain the interlace flag
 > identifying fields that belong together just like on DVD?

Probably depends on the encoder of the channel provider. We don't
change anything about the elementary stream.

 > 
 > For film this normally helps to combine the both interlaced fields that
 > belong together into one non-interlaced frame. For video you have to use
 > some more intelligent algorithm to avoid the zick-zack lines, because
 > her the source is really interlaced.
 > 
 > I assume the video4linux device just places the interlaced image into
 > the frame buffer. This looks just awfull with programs like kvdr on a
 > large screen (I have a beamer). Currently the image from the S-video
 > feed through my scaler, which scales it to 1024x768 anamorph, looks much
 > better then any progressive image from the graphic card, even the scaler
 > cannot do 2:2 pulldown. The scaling to a higher resolution smooth the
 > edges at the cost of sharpness. 

It depends on the driver. The bt848 driver puts the half frames into
separate pictures, if the size is smaller than half the TV resolution.
I haven't checked what the saa7146 does in that case. 
If your graphics card supports Xv than xawtv uses the hardware scaler
of the card to scale the picture to full screen size. In this case you
may still get a line running through the picture, because v4l device
and graphics card are not in synch.
Maybe you may want to check out DirectFB, the developers were working
on synching the v4l output to the output of the graphics card. They
had it working for Matrox cards, but I don't know if they have other
cards working and if it is included in the latest version.

Marcus


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