My cpu is monocore (AMD Athlon(tm) 64 Processor 3500+), so probably there won't be any difference with a multithreaded player.
Anyway I think there is no cpu problem, since I'm testing with low resolution videos that keep cpu at 20-30%.
I've tried with "ffplay" command, same result as with mplayer.
I've also tried "glxgears" command. It gets ~58 fps with window maximized, and cpu at ~20%. But I can see that the rotation is not fluid every ~0'5 seconds. What does it mean?
Can I try anything more?
I'm starting to think in a defect in hardware (graphic card or motherboard).
A 25fps video on a 60Hz monitor will *never* be smooth. Your TV should be able to render at 50Hz or 100Hz but the card is probably vsyncing to your primary monitor (60Hz) so this won't help. (The same happens on Windows, too).
As a test, try setting the TV as your primary monitor and/or disabling the TFT completely.
As BlackStar has suggested, the cause of the not fluid video was the difference between the file frequency (25 fps) and the monitor frequency (60 hz):
60 can't be obtained from multipling 25 by some integer number, so the number of frames shown in a second are variable from one second to other second, so the video is not fluid.
The solution has been to change the monitor frequency to 75 hz (50 hz is not available in my monitor). Now the video is very fluid in my monitor. I think it's not totally totally fluid due to the high response time of the monitor.
But I haven't been so lucky with the tv: It doesn't support 50 or 75 hz, only 60 (at least with the vga cable). I've been playing with modelines, trying to force 1920x1080 50Hz and 1920x1080 75Hz, even 1280x720 75Hz, but none of them works, tv says "No signal". Do you see, from the xorg log I posted, some modeline at 50hz or 75hz I could use? (preferably at 1080 or 720 resolutions (hd))
Perhaps the 60Hz is a limitation of the vga cable. Maybe the tv supports 50 or 75 Hz with a dvi-to-hdmi cable, but I'd prefer to be sure before buying the cable. Do you know if tvs usually support more modes in hdmi input than in vga input? The tv manual is not clear (no distintion between vga and hdmi imput).
Yes, I know the tv panel has 1920x1080 pixels, and that other resolutions are scaled to that.
I meant that the tv vga input only accepts 60hz in a 1920x1080 signal, but perhaps accepts 75hz (or 50hz) in a 1280x720 signal. If that is possible, I know the tv will scale the signal to 1920x1080, but the important point is that the video will be fluid (for a 25fps video, since 75=25x3 (or 50=25x2)).
The optimal solution would be the tv to accept 50 or 75hz in a 1920x1080 signal, but it doesn't look possible with the vga input. Perhaps it's possible with the hdmi input, but I don't have a dvi-to-hdmi cable. Perhaps I'll buy the cable, and will return it if doesn't work.
I'm going on vacation now, will return in some days. Merry christmas to all of you.