Hi Tim...

Tim Wassink wrote:
> Hi,
> 
> This is my second post of this "behaviour" (can't call it a problem).
> I didn't receive any comments the first time, but I hope for the best 
> this time.
> I know you all are busy, but if you could find the time that would be 
> great...
> 
> The short version is:
> Can I change a setting so that the shadows around the text of the menu 
> will disappear?
> If this is due the limitations of the mpeg2 decoder in the mvp, then I'm 
> out of luck.
> The longer version is in the original post below.
> 
> Thanx in advance,
> 
> Tim
> 
> --Original post---
> Hi,
> 
> I was wondering if I could get rid of the shadow around the text in a 
> captured screen capture, which
> is encoded by vlc in mpeg2.
> 
> You can also see this shadow in the menu of mvpmc.
> see this link to jpg photo of the "ngs" of settings (33kB) 
> <http://vfit.nl/projects/mvpmc/text_schadow_mvp.jpg>
> 
> Can I change a setting to make this disappear.
> 
> The following is what I want to do:
> 1. screen caputere (dvd size 720x576), transcode this to mpeg2(bitrate 
> 8Mbps) with VLC.
> 2. display this stream with the mvpmc
> everything works great, except the shadows.
> The artifacts, which are there in lower bitrates, are minimal and 
> acceptable with 8Mbps.
> 
> 
> I know it's mpeg2 encoding, which isn't the nicest way to display text, 
> but when I connect
> with VLC from another pc to the generated mpeg2 stream it looks very nice.
> 
> I've tried a expensive scart cable(gold plated, foil), but there was no 
> improvement.
> I suspect the mvp mpeg2 decoder to generate the shadow.
> Can I change some settings to make it better?
> 
> Thanks in advance.
> 
> Regards,
> 
> Tim

I don't mean to doubt you, but is this really a screen capture or a 
picture taken with a camera of your TV?  It just looks a lot like a 
signal reflection from bad terminations or delayed response of some old 
picture tube.  Further, and I'll be the first to say I am not entirely 
sure about this, MPEG encoding artifacts should be distributed *around* 
objects.  That is before, below, above & after a sudden change in the 
encoded picture.  Your image shows artifacts to the right of the 
picture.  If you did take the picture using a camera - try using the 
green button on the MediaMVP's remote control while running just about 
anything other than MClient.  You will need to use the proper option on 
the mvpmc command line (in your dongle configuration file) to indicate 
where to save the screen capture.  This method would eliminate any 
problem with your video cable or TV.  My guess is that your cables are 
fine, but you have bad termination.  If the impedance of the cable, the 
source of the video and the destination of the video do not match - the 
signal will bounce back and forth between the ends of the cable.  The 
longer the cable, the longer the delay and the artifact or "reflection" 
of the images will appear further to the right (TVs scan from left to 
right).

Given the above, let's see, SCART - so your picture is being refreshed 
50 times/second.  Horizontal scan is about 15KHz.  There might have been 
40 chars across the screen. The echo looks like 1/4 of that.  About 30% 
of the Horizontal scan is wasted in blank screen and synchronization 
pulses.  So [(1/15K)/[(1/.3)*40]]*(1/4)=125E-9 seconds.  Light is 
3E8m/s.  So 3E8*125E-9=37meters.  Hum, that sounds long.  Are you using 
a 37 meter SCART cable???  Well, there's a lot of guessing going on 
here.  For instance signals do not travel at the speed of light through 
a cable - it slower - which would make the calculated cable length 
shorter.  And if these characters were smaller than I am guessing (like 
say you could fit 80 across the screen) that would just about half the 
calculated cable length.




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