The Fugue

A while back I posted about chiles rellenos. Now there’s a video.

I bought an MSI NX6200AX-TD256H D2 video card (It’s an NVIDIA GeForce 6200 256MB 8x AGP card) to drive the MythTV frontend, since MythTV can’t manage to play even the most modest content using my trusty old Radeon 7000 (MythTV doesn’t support VIDIX, only XVideo). I hoped that the upgrade would allow me to watch live HD television, which means XvMC.

Before I go any further, the other relevant stats: the computer I’m using (for the purposes of this post, anyway) is an 64-bit AMD Athlon 2800+ running 32-bit Ubuntu 8.04. The motherboard is a VIA K8T800. I’m actually using TwinView to share the Desktop computer with MythTV, but I tested everything with a single-screen (the CRT) to avoid confounding, and using TwinView doesn’t seem to make a difference one way or the other.

All the normal stuff works great, but XvMC does not though it should. Whenever I try to use XvMC, the client (mythfrontend or mplayer, for example) freezes up and must be killed. I tried all the standard tweaks that Google could suggest: enable/disable sync on vblank, enable/disable OpenGL vsync, various xorg.conf settings. I tried just about everything I could think of and then some, and the only thing to make any difference at all is this setting in xorg.conf:

Option "NVAGP" "0"

That is, I disabled AGP. When I do this, XvMC works as it should. After a little research, it perhaps shouldn’t be too surprising that AGP is the problem on a VIA motherboard. At least it’s a lead.

Interestingly, when I downgraded the driver from the latest (173.14.05) to the newer legacy driver (96.43.05), XvMC works fine with AGP enabled. As one would expect, it outperforms the newer driver with AGP disabled. Here’s a performance table:

               (% CPU when playing SD/HD in MythTV)
Driver                       Xv     Xv+linear    XvMC+bob
173.14.05 (AGP disabled)  20/100+    30/100+      12/60+ (OSD is too much)
96.43.05                  20/100+    30/100+       8/45

There’s a few caveats to XvMC, either way I get it to work. When deinterlacing is on, the OSD gets deinterlaced too. This isn’t a pretty sight, though it’s functional. The OSD is always grayscale, in spite of setting XvmcUsesTextures to false in xorg.conf and choosing chromakey. But that doesn’t bother me much, I don’t much like the color schemes of the OSD themes I’ve seen.

I have one more straw to grasp before I consign myself to using the legacy
driver (which I may do if it runs FlightGear and X-Plane ok) or crossing my
fingers for a fixed driver before the Olympics (I intend to submit a bug
report). I’m going to try poking around with AGP driving strength settings in
the BIOS. I tried 0xEA and X wouldn’t start at all, but with the same symptoms
I get with XvMC. That hints at the same cause, so maybe with some kind of
binary search I can stumble on a compatible setting.

So in conclusion, I’m going to try using the legacy driver even though my card is supported by the newer driver, and for OSD reasons only use XvMC for HD.

I have a 64-bit desktop machine, that has rarely been run as a 64-bit machine. The hassle was too great and I couldn’t really see a reason to put up with it.

I think that 64-bit support has come a long way in the meantime, and it may be time to try it out. It sounds like a livable situation. So with the pending release of the next Ubuntu version I’m thinking of wiping and going 64-bit.

One of the primary motivators is that 64-bit holds some promise for transcoding video, and now that I have an HDHomeRun to capture over-the-air HDTV signals, I will be doing quite a bit of video transcoding for MythTV (to save disk space—a full-quality HDTV program is about 9 gigabytes per hour).

But before taking the plunge, I thought I’d do an empirical test and see if there would be any real savings. I captured a couple of minutes of HD content from PBS, then transcoded 60 seconds using ffmpeg and mencoder. Then I did the same with the Ubuntu 64-bit live CD. The 64-bit execution difference was statistically significant.

ffmpeg was about 1.12 times as fast—a savings of about 10 seconds per minute, or 10 minutes per hour.

mencoder was about 1.08 times as fast—similar savings.

I didn’t test mythtranscode itself, since getting it installed in a live CD environment would be too much work. I also must point out some other possible confounding variables. I used the Ubuntu 7.10 versions of ffmpeg and mencoder in 32-bit, and the Ubuntu 8.04 versions in 64-bit. Did both projects improve their code to be about 10% faster in the meantime? Unlikely, but perhaps not unfathomable.

So will I make the switch? I don’t know yet. 10% faster is significant, but not obviously worth it. I’ll have to think about it.

For the curious, here’s my numbers. I did at least two runs of each to check for agreement, and what you see is the average. Of course, these would not be the settings you’d necessarily use to transcode—ffmpeg has a pretty low default bitrate for example—but I think we can agree the speedup is likely to be in the same ballpark no matter what settings you’re using.

# 64-bit    32-bit
# 86 s      95 s
time ffmpeg -y -t 60 -i foo.avi -acodec copy bar.avi
# 55 s      64 s
time ffmpeg -y -t 60 -i foo.avi -acodec copy -s 640x480 bar.avi
# 83 s      90 s
time mencoder foo.avi -oac copy -ovc lavc -frames $[30*60] -o baz.avi

In a quest for technique tips on baguette forming, I found a page at The Fresh
Loaf with some great tips on bread
slashing. Even more importantly, the page includes a nice
video.
I don’t like the bread with such deep slashes, I prefer shallow and more
slashes. In any case, the technique tips are pretty good.

But the real gem here is the link to Le Petit
Boulanger which is le site de la boulangerie
artisanale. I don’t speak french, but I know enough to follow the silent videos
(with one exception) posted in the
Vidéos page. They are excellent videos
of a real boulanger showing you how it’s done. Notice how supple the dough is -
obviously fairly high hydration. Notice how firmly but gracefully he moves the
lame. Notice his neat coat.

So anyway, my conclusion is that the scalpel I got from the bookstore is
probably not sharp enough. I’m going to get me some coffee sticks and
double-edged razor blades and use a more acute angle. Hopefully I’ll stop
tearing the loaf and get some nice slashes like the ones you see in those
videos.

For some time now Slashdot has ben getting more and more immature. Or I’ve been getting less tolerant of immaturity. I’m not sure which.

A story run yesterday was the last straw. It’s time to move on. I’m removing Slashdot from my RSS feed.

The story was entitled Unrefined “Musician” Gains a Global Audience. Here is the blurb:

“An unskilled musician performed a catchy pop instrumental for more than one
million YouTube users even though he can’t play a lick of drums or piano. The
22-year-old Norwegian’s tool was stop-motion video,

Hey Slashdot, guess what? If you compose music that people enjoy (i.e. catchy), you don’t qualify as unskilled musician. This guy is obviously skilled at many things. He can obviously compose a catchy tune, knows a lot more about drums than I do, is very skilled with a video editing program, has a good comedic sense, and is good with a tracker. I know a number of composition majors at BYU who can play about as much piano, drums, or anything else as this guy. He and they compose music nonetheless and they are skilled musicians.

Skilled performer? No, at least not with those two instruments. But a skilled musician and video creator. Go watch Lesse Gjertsen’s Amateur and Hyperactive. They’re enjoyable.

Goodbye Slashdot, this reader has decided to leave your unrefined “news site” for the script kiddies.