HTPC linux hardware gotchas

[avuton]

you should know that open source drivers, nvidia and ati as well are not able to enable 24p (24hz or multiple, whatever) on the TV that supports it.
Proprietary drivers can, and when you have 23.976 frame per seconds videos to display, like almost all movies and tv shows, this is very nice to not have any stutter or judder.

OK, from my understanding that doesn't affect someone watching NTSC/Pal movies (non-drm Bluray or the such, right?)

Thanks again;

[bridgman]

EDIT - starting over

Looks like 1080p/24 is supported by :

- BluRay disks (where 247Hz output from player to display is common),

- ATSC (North American digital TV standard) using H.254, although since most digital TVs only handle MPEG2 there probably won't be that much 1080p/24 broadcasts for a while

- some DVDs (I didn't know this before, not sure if any players will output 24Hz from an appropriate DVD)

NTSC and PAL broadcasts do not have a 24 Hz option. Not sure about non-US digital TV standards but will check.

Anyways, unless you have a very spiffy-new 120 Hz TV it's not clear that you get a benefit by sending 24 Hz to the TV and having the TV do 24-60 Hz vs having the 24-60 Hz conversion done in the player application and outputting directly at 60 Hz.

[mirak63]

Anyways, unless you have a very spiffy-new 120 Hz TV it's not clear that you get a benefit by sending 24 Hz to the TV and having the TV do 24-60 Hz vs having the 24-60 Hz conversion done in the player application and outputting directly at 60 Hz.

First HDTVs were just "24p compatible" wich ment that when input was 24p they where doing the 3:2 pulldown conversion, from 2fps to 60hz or 50hz.

However some recent TVs, of about half a year old are doing real 24p and display in a refresh rate multiple of 24hz. My TV supports it, and you really get a judder free playback.
My TV is not 120hz, I think it just physically supports 48hz, it's a Sony KDL W4000. However the proprietary drivers tricks Xorg to believe he is really in 24hz.
Most TV shows I downloaded (since I don't live in US) have a frame rate of 23.976, and I guess they are broadcasted like this.

If you don't think there is a noticeable difference between a real 24hz playback and 3:2 pulldown to 60hz, then you probably did not experienced it. The difference is really noticeable on large flat panels. That's not just marketing, it removes stutters.

Opensource drivers will probably supports it one day, when more people will request it, and once developpers realise how benefical it is to the quality of the playback, and also how the proprietary drivers are triggering it.

[bridgman]

Yeah, the 48Hz native refresh option is the interesting one. I have heard about it for a while but when I try to find confirmation I didn't have much luck. There seems to be a lot of debate about how the KDL W4000 actually works, but I agree that 24Hz input doubled to 48Hz refresh seems the most likely.

Given that 48 Hz is so close to 50 Hz maybe this is something which makes sense in PAL and SECAM markets but not so much in NTSC-land. I'll have to look at European TVs and see what I find there (actually I guess I'll start with the model you identified ).

I agree completely that if the TV can display at 48 Hz without doing any more than frame doubling or interpolation then having a 24 Hz output from the card is definitely something useful.

EDIT - many of the Google hits on 48 Hz display of 24 Hz material lead back to this thread

[bridgman]

My TV is not 120hz, I think it just physically supports 48hz, it's a Sony KDL W4000.

OK, I did some more digging. It seems pretty likely that your set *is* 120Hz.

The 3000 series took 24p and displayed at 48 but most indications are that the W4000 series displays at 120 Hz.

Nice

[mirak63]

OK, I did some more digging. It seems pretty likely that your set *is* 120Hz.

The 3000 series took 24p and displayed at 48 but most indications are that the W4000 series displays at 120 Hz.

Nice

The european version of w4000 is different and i think not 120hz at all.
If it was just a edid limitation it would be nice, but for europe models i doubt it is.

[bridgman]

According to all the posts I saw the Euro model (W4000) and the NA model (W4100) are identical internally. It's always hard to be sure though...

Anyways, the one clear thing is that all we need is 24-ish Hz output, no need to worry about 48 or 72.

[bitnick]

What stops the OSS drivers from outputting at 24 Hz? Without knowing any specifics, it seems strange that the X server/xrandr would reject those specific modes?

I know there are "soft" limits to vertical and horizontal refresh rates (to prevent people from destroying very old monitors?), but those can (could?) be circumvented with the VertRefresh and HorizSync options in the Monitor section of xorg.conf.

[bridgman]

Honestly, I think the "big problem" is that the issue hasn't come up before so nobody has really looked at it -- and most of the devs are off doing other things today (or are still hung over ). There's probably a 50/50 chance that the current drivers can be made to work with the right combination of settings, and if that doesn't work the changes would probably be small.

[mirak63]

hi,

have any update on this bridgman