Televisions and refresh rates

carl67lp

Supreme [H]ardness
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I was going through the Gentoo/MythTV guide the other night and once I had a picture on my TV, I was a bit put off by the refresh rate. I think I have hsync at 60 and vsync at 30-50 or something like that, but that's just because I pulled it from the guide.

How can I figure out these values to plug in to my XFree config? My television manual is nowhere in sight.
 
carl67lp said:
I was going through the Gentoo/MythTV guide the other night and once I had a picture on my TV, I was a bit put off by the refresh rate. I think I have hsync at 60 and vsync at 30-50 or something like that, but that's just because I pulled it from the guide.

How can I figure out these values to plug in to my XFree config? My television manual is nowhere in sight.

If it is a standard TV in the US, then the refresh rate is 60hz interlaced. No changing that either. Reason is the refresh rate is set via the AC rate, which is 60hz. Actually the frame rate is half that since standard def is interlaced so that is 30hz for the frame rate.
 
m1abram said:
Actually the frame rate is half that since standard def is interlaced so that is 30hz for the frame rate.
Actually, its 29.97, but that's only if you're going to be picky.
 
Thanks. Makes sense.

Actually, only the parts of the MythTV setup that have text look a bit off. Everything else, including regular menus (where the text is actually in images) and the live/recorded video is fine.
 
theacoustician said:
Actually, its 29.97, but that's only if you're going to be picky.
Actually, interlaced content can't be called 30 fps unless the source material is 30 fps. Interlacing uses a framerate of 60 half-height frames per second (odd lines and even lines). For 30 fps content, both odd and even lines come from the same picture. For 60 fps content, all odd and even lines come from different images, and only in still areas do they line up to give your the full vertical resolution.
 
for my pvr350 tv out it is set to

Section "Monitor"
Identifier "NTSC Monitor"
HorizSync 30-68
VertRefresh 50-120
Mode "720x480"
# D: 34.563 MHz, H: 37.244 kHz, V: 73.897 Hz
DotClock 34.564
HTimings 720 752 840 928
VTimings 480 484 488 504
Flags "-HSync" "-VSync"
EndMode
EndSection


otherwise the settings you mentioned work on my MX440 just fine
 
DrT said:
Actually, interlaced content can't be called 30 fps unless the source material is 30 fps. Interlacing uses a framerate of 60 half-height frames per second (odd lines and even lines). For 30 fps content, both odd and even lines come from the same picture. For 60 fps content, all odd and even lines come from different images, and only in still areas do they line up to give your the full vertical resolution.
Uh, yeah. Call it what you want. NTSC standard is 29.97 fps. Calling it 30 works in most cases, except when you are transcoding or some other special operations. Then it matters and you have to be right at 29.97.
 
Sorry if I was too lazy to type 29.97 and 59.94, but I was pressed for time ;) You're right of course; NTSC is 29.97 *frames* per second, but what I was trying to get across was that those frames are in fact made up of 2 fields, and the TV displays 59.94 fields per second. If the source is 29.97 fps, those 2 fields will come from the same point in time; if the source is 59.94 fps, those 2 fields will come from different points in time, in which case the temporal resolution of NTSC can be up to 1/59.94 of a second.
 
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