[mythtv] Some questions about mythtv's technology

mythtv-dev@snowman.net mythtv-dev@snowman.net
Fri, 19 Jul 2002 17:28:46 -0400

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I took a look at some of your project's notes and screenshots as well
as some list messages.  I have a few questions.  I am developing a
"set-top" linux PVR as well so I am quite familiar with all of the

First of all, I have gathered that you are using X11 and the Xvideo
extension for your output.  How do you control flipping the images of
a video stream from one frame to the next such that they only get
flipped on the vertical retrace (vsync pulse).  As I understood it,
this was not possible in X11/Xv.  If you can't do this, then you must
get horrible tearing of your displayed video streams.

I have also gathered that you are using the Nuppel video format.  I
have not really looked much into this format myself, but does it store
field information (i.e. interlaced streams) or is it progressive like
MPEG1 and store frames?  If it's progressive like MPEG1, how do you
deal with the temporal issues of two fields, each being a different
snapshot in time being combined together into a single frame?  Do you
get interlace artifacts or does Nuppel have some
"smoothing/blending/interpolating" algorithm to combine the two fields
into a single frame?

Do you not feel that an interlaced storage format that saves the
temporal information from two fields is better suited when your output
target is an interlaced device like a television?


Brian J. Murrell

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