On 5/31/06, <b class="gmail_sendername">James Buckley</b> <<a href="mailto:james@logicland.co.uk">james@logicland.co.uk</a>> wrote:<div><span class="gmail_quote"></span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Hello, I've been building my Myth box for well over 3 moths now; everything<br>works except for one major problem, TV playback (lol).<br><br>I find that TV playback with either no deinterlacing or non BOB<br>deinterlacing just doesn't have enough frames a second to be watchable. For
<br>example, if you compare news tickers you get on sky news or BBC news, over<br>normal Freeview / DVB-T, they are much smoother than through MythTV. Unless<br>I can get the tickers to be as smooth as normal TV (or very close to), I'm
<br>gonna end up scrapping this project, something I really don't want to do.<br><br>My setup is as follows, I have a Myth box running latest SVN build,<br>outputting over DVI (from a Nvidia 6200 chipset) direct to my LCD TV. I
<br>haven't created a custom modeline, as I can get crisp, no overscanning<br>output, using the resolution 1360x768, progressive. Now, the solution to a<br>low frame rate is to use BOB deinterlacing, this makes TV smooth, but has
<br>some very horrible side effects.<br><br>1. The video jumps up and down, not a little bit, but really noticeably<br>2. The OSD goes horrible, hard to describe, but you no what I'm talking<br>about<br>3. Any Interactive overlays, like "push the red button" are given the same
<br>effect as 2.<br><br>Certain scenes on TV go really horrible when using BOB deinterlace, for<br>example anything with lots of horizontal lines is almost unbearable to<br>watch, as they jump up and down, also text (as this has horizontal lines
<br>also) is jumpy, on the news tickers it jumps , and cause it's close to the<br>edge of the ticker, it's really noticeable.<br><br>I'm sure it can't just be me who can't put up with these problems, so does<br>anyone have an idea what causes these, what can be done to minimise them,
<br>and if there are any alternatives to BOB deinterlacing, but still doubling<br>the frame rate.</blockquote><div><br>I think you are running into a combination of several problems:<br><br>- Bitrate. Ticker lines seem to be very hard to compress into MPEG2. So to have soft moving ticker lines you need as high a bitrate as you can get if you record from an analog signal. If you record from a DVB signal then you can not do anything at that point. Having MythTV record a DVB signal should be as good as using any other DVB receiver.
<br><br>- Frame rate. If the frame rates in your system do not match, then you will get some kind of low-frequency disturbance. There are three frame-rates to consider. You receive a signal with some framerate. In the UK you use PAL-I which have 50 half-frames per second. Then your videoadapter sends the videosignal to your monitor. If you do not modify your modeline, it will probably send 60 or 70 full-frames per second. By deinterlacing you will convert the 50 half-frames to either 25 full-frames or 50 full-frames per second. Both will give some low-frequency disturbance when you output with 60 or 70 full-frames per second. You should find a better modeline. Third your LCD-monitor has an internal refreshrate. The LCD pixels are mounted in a grid and only one row of pixels are updated at a time. Some older monitors have a fixed refresh rate at 60 frames per second. If that is the case, it will never look very good, especially not if your videoboard outputs at 70 frames per second.
<br><br>- Deinterlacing. Bob will make OSD and similar jump up and down. I did not like it, so I chose the linear deinterlacing instead.<br><br>Niels Dybdahl<br></div></div><br>