Hiccups

I've developed a new problem with the Xvideo rendering system. The movie will jerk occasionally, usually during slow pans or tilts. The cause must at a low level as mplayer is not giving the usual, "Your system is too slow to play this," message.

I first noticed the problem with the final release of 2.6.37 but it exists in the -rc7 release as well, although the effect is a lot less frequent. I'm going to try the 2.6.36 kernel next. If the problem occurs there as well, I'll know that the cause is not the kernel, because 2.6.36 worked perfectly before.

Sigh. I'll be glad when the AMD graphics support stablizes a bit. It is improving but there are plenty of hiccups (literally, in this case) along the way.

Linux, KMS, 3D, ATI, Oh My!

Yesterday I realized that accelerated 3D rendering no longer worked on my ancient ATI R200 based card. After some experimentation, I discovered that ATI accelerated 3D graphics now requires Kernel Mode Setting (KMS) to be enabled. This was a huge problem because Xv, the X accelerated video rendering system, has diagonal "lightning strike" tearing when used with KMS. I really wanted 3D back, though, so what to do?

Today, I was bored with work, so I decided to play with the ATI R600 based card which I bought way back in the spring. Initially it was very disappointing. The X server crashed almost immediately which was a regression from earlier tests: not a good sign!

Examining the system logs indicated that the problem appeared to be in the kernel, not the X server. I've been running a 2.6.34 kernel from Debian experimental and it so happens that a 2.6.36-rc6 kernel was available. Installing the newer version fixed the X server crash! Yay!

Accelerated 3D rendering now works on the R600 card but what about the tearing in Xv? Frankly, it was a bigger concern than 3D. If Xv didn't work, I would have to go back to the R200 card, which still supported an Xv mode that worked without KMS, and all this effort would have been for naught. So it was a great relief to discover that the Xv tearing problem has been fixed on the R600 card. Double Yay!

It's not often that one accomplishes anything while avoiding work, so I'm quite pleased with today's efforts. It's been a good day!

ATI 3D On Linux

According to this article, the open source 3D drivers for the older ATI R300-R500 graphics processors are much more mature than the newer generation R600/R700. I suspect that this indicates the age of the hardware that most developers own, but I could be wrong. I wish that I had known this before I bought an R600 based card. ^^

Not that it really matters, as cards using the earlier generation processors are quite difficult to find, unless you go the Ebay route. I'm still leery of buying electronics on Ebay. Call me paranoid...

A Little Too Optimistic

My expectations of the open source support for more recent ATI GPUs was a little too optimistic. I bought a card based on the Radeon 3650 GPU which is released in 2008. I had no problem with basic 2D support. The first sign of trouble was when mplayer stumbled rather badly. The X server does not have Xv Video Overlay support for the 3650, which might be the problem.

3D support was much worse. I couldn't get a single 3D application or game to run properly. I was so hopeful that the ATI support was getting better, but it looks like it has some ways to go yet.

There may be tweaks one can use to get it working better, but I ran out time today. Since I depend on mplayer to work properly, I put the old graphics card back for now. I try the new card again after the next X server upgrade.

Old And Slow

I started playing with with 3D modelling software (Blender, Wings 3D, and MakeHuman) and was graphically (pun intended) shown just how old and slow my ATI 9250 graphics card really is. The older GPU has are several problems which are individually tolerable, but, when taken together, you've basically hit a wall.

I'm shopping around for a replacement card. I have three basic constraints: I'm on a very tight budget, I want an ATI GPU, and it must be an AGP card. AGP?! Yup, I'm not replacing the motherboard yet (see constraint #1) so that's the way it has to be. An older design such as this ATI 3650 should be adequate.

Nvidia may offer better performance but that really only matters to serious gamers. Nvidia's closed source Linux drivers are actually very good, but since AMD released the programming documentation for ATI GPUs, the open source drivers for have been improving slowly but steadily. They are far from perfect yet but with proper documentation available, it's only a matter of time.

Kernel Mode Setting

It looks like Kernel Mode Setting (KMS) for ATI chipsets has arrived on my Debian sid desktop system. As usual, I only realized this was happening after mplayer started complaining about the system being to slow. Errors in the X server logs revealed that indeed the Direct Rendering Infrastructure (DRI) was not working. Without DRI hardware acceleration, mplayer is definitely going to have trouble playing 720p video with soft subtitles.

This article indicated that the X server version was OK but I needed the latest Debian kernel package (2.6.32-10), which did indeed fix the DRI error and made mplayer much happier. However, it is not perfect. There are now artifacts appearing in the video during fast pan or tilt scenes. Even in an xterm, rapid scrolling results in noticable discontinuities.

The article mentions needing new microcode for the graphics chip. I haven't yet discovered if such microcode actually exists for the ancient R280 chipset on my ATI 9250 card. Or the problem may lie elsewhere. More digging is required. ^_^