Thursday, February 24th, 2005
While procrastinating by surfing the internet, I stumbled across an article on overcoming procrastination. I love his “Get Back to Work” home page idea.
Wednesday, February 23rd, 2005
Trimble presents a very straight-forward explanation of how GPS works that I enjoyed.
Tuesday, February 22nd, 2005
I’m currently taking a course on digital video processing given by Prof. Thrasyvoulos Pappas, my advisor in the Image and Video Processing Laboratory (IVPL) at Northwestern.
For the course project, I’m studying objective image quality metrics, or the computation of a number that corresponds to the perceived quality of an image.
One image quality metric that is often used when comparing a reference and degraded image is the mean squared error (MSE), computed by simply averaging the squared differences between the reference and degraded image. For example, the degraded image could be a highly compressed version of the reference. While MSE is simple to understand and easy to compute, it does not achieve a good correspondance with perceived image quality.
Some interesting image quality methods have been proposed and tested recently. Junquig Chen from the IVPL evaluates metrics used when optimizing image compression, comparing MSE with subband, wavelet, and DCT-based metrics (see the SPIE paper).
Also, some very intersesting work has come from Eero Simoncelli’s Laboratory for Computational Vision (LCV) at New York University. Zhou Wang’s work on his Structural SIMilarity (SSIM) index is the best approach I’ve found so far for quantitatve evaluation of image quality for many different applications.
In upcoming blog entries, I hope to summarize and review some of the most interesting and influential papers that deal with image quality. I’ll start with Zhou Wang’s “Image Quality Assessment: From Error Visibility to Structural Similarity”. Stay tuned ….
Monday, February 21st, 2005
It’s that time of year again — time to prepare for the 2005 Cubs season by desperately trying to get tickets.
They go on sale this Friday, February 25th. The online “waiting room” is open at 9:30 a.m. and then sales start at 10:00. Also, you can get a wristband Wednesday or Thursday and if you’re lucky, acquire some tickets in person at Wrigley Field on Friday. For more information, check out the Cubs single-game ticket instructions.
Tuesday, February 15th, 2005
Faster LAME for TiVo AAC Playback
In my previous post, I was hoping to speed up the AAC-to-MP3 transcoding by compiling LAME on my own. This turned out to be very easy and gave quite an impressive performance improvement.
Here are the steps on the command line for a G4 (from the blacktree forum). Note that the multi-line commands should be entered on one line.
$ cd ~
$ mkdir tmp
$ cd tmp
$ curl http://internap.dl.sourceforge.net/sourceforge/lame/lame-3.96.1.tar.gz -o lame-3.96.1.tar.gz
$ tar xvzf lame-3.96.1.tar.gz
$ cd lame-3.96.1
$ ./configure CFLAGS="-O3 -falign-loops-max-skip=15 -falign-jumps-max-skip=15 -falign-loops=16 -falign-jumps=16 -falign-functions=16 -malign-natural -ffast-math -fstrict-aliasing -funroll-loops -floop-transpose -mpowerpc-gpopt -fsched-interblock --param max-gcse-passes=3 -fno-gcse-sm -mcpu=G4 -mtune=G4"
$ make
$ sudo make install
$ cd ~
$ rm -rf tmp
After compiling, I compared the resulting binary program in /usr/local/bin/lame to the fink-compiled lame and found that the optimized version was 3.6x faster (7 versus 25 seconds) at compressing an mp3 with the default options.
This optimization reduced my processor usage while transcoding with TiVo from 80% to 25%.
Tuesday, February 15th, 2005
TiVo Desktop 1.9 Plays AAC Files
After digging around to learn more about TiVo Desktop 1.9 for Mac OS X, I learned about an interesting hidden feature: you can play back AAC files on your TiVo by using a transcoding feature.
On the TiVo Community Forum thread about version 1.9, a user describes that you can use LAME to transcode unprotected AAC files. This doesn’t get you iTunes Music Store DRM’ed AAC playback, but if you’ve ripped many other CDs in AAC (like I have), you’ll be quite happy about this.
The basic idea is:
1. Install the lame command line program in /usr/local/bin/lame
(or do “fink install lame”, then “ln -s /sw/bin/lame /usr/local/bin/lame”)
2. Stop and re-start TiVo Desktop via the Preference Pane
3. Enjoy
On my dual-800 G4 powermac, the fink version of lame used about 75% of one processor to do the real-time AAC to MP3 conversion.
Alternatively, I’m hoping that compiling lame using an optimization suggested on this blacktree forum will give me an improvement.
Saturday, February 12th, 2005
Grab the update from TiVo or Versiontracker.
Here’s the blurb direct from TiVo:
This update contains: a revised preferences mechanism, support for photo album heirarchies, a new plug-in API, and minor bug fixes.
I installed the TiVo Desktop 1.9 update on my Mac and I was happy to notice that the background process that runs when TiVo Desktop is on is much more efficient. With 1.8, cpu usage was 3-7% all of the time, even when I wasn’t playing music or looking at photos on TiVo. With 1.9, the cpu usage is 0.0% with occasional spikes to 0.9% — much improved.
Also of interest was some of the information displayed by the installer. Here’s a snippet:
Changes since version 1.8 * TiVoDesktop can now work with applications other than iPhoto to share photos. * Enhances performance and stability.
I wonder what applications other than iPhoto they have in mind?
Unfortunately, this update does not support TiVo To Go or the playback of AAC files in Music & Photos. For Mac users, waiting is.
Saturday, February 12th, 2005
This hilarious FAQ discribes TiVo in a unique way. It made me cackle.
