[linux-dvb] Re: Recording using a TwinHan VisionDVT terrestial card

[Hamish Moffatt <hamish@cloud.net.au>]

On Thu, Jun 10, 2004 at 09:43:02AM +0200, Måns Rullgård wrote:
> > Finally (yes!), a question about image quality: when I view live,
> > or play back a recording, there seems to be some interlacing
> > problem or similar. Fast vertical movements reveal horizontal
> > lines, most obvious when a TV program is using a blue screen
> > background for adding graphics, such as a weather report, but
> > disturbing also when watching regular programs.
> 
> That is because the broadcasted stream is interlaced to play back
> nicely on a regular TV.  Try activating some deinterlacing in your
> playback software.

I've been reading about this recently and I don't think your explanation
is accurate. For example, when you watch analog TV the picture is also
interlaced but you don't see the jagged edges.

The problem isn't that the picture is interlaced, but that your display
device refresh is not synchronised with the field(frame) source. As a
result, you see the transitions from one field to the next, as jagged
edges where an object moved.

Unfortunately the most common solution is to blur the jagged edges. 
It gets rid of those but it does make fast panning look a bit unnatural
IMHO.

I think that, in theory, if you could synchronise your update rate with
the frame rate, you would not need deinterlacing. MythTV has some code
which attempts to do this.


Hamish
-- 
Hamish Moffatt VK3SB <hamish@debian.org> <hamish@cloud.net.au>