Yearly Archives: 2009

Star-Shaped Discs

I purchased a Sony PlayStation 3 recently. I thoroughly read the accompanying manual on a train ride and a particular detail caught this optical media aficionado’s eye:


Sony PlayStation 3 manual -- disc shape notice

Wait… what? Star-shaped discs? Heart-shaped ones as well? Are those real? How would those even work? I know about 80 cm discs that fit in the smaller groove of a CD tray. I also know about the business card-shaped CD’s; I even have a few games that were published on such a form factor (for example). But a star has points. And a heart? How?

A brief bit of Googling for “star shaped disc” leads me directly to the Wikipedia article on shaped CDs, which happens to showcase a heart-shaped CD. But how would a star-shaped disc work? That (typically) has 5 points. Where would the circular track go, the one that holds data? I figure there could be sort of a fat star, a circle with 5 points. This turns out to be the correct idea as this disc manufacturing page indicates.


star-shaped-cd

Check out the page and see the oddest shape– the house CD.

Latest FATE FRExt Tests

I staged 19 new FATE tests today which will finally push FATE over 300 individual test specs once I activate them tomorrow. The first 12 were a dozen more fidelity range extension (“FRExt”) H.264 conformance vectors. Thanks to Carl Eugen Hoyos for doing the validation on these vectors and informing me of the right command line options to get the output correct.

These are the other tests I entered:

I’d also like the recognize Michael K. once more for his FATE contributions in the testing “other” platforms category. In the last week, he started contributing FATE results for x86_64 variations of both OpenSolaris and OpenBSD.

Theora 1.1 Released

No sooner did I press “Publish” on my last post pertaining to multithreading FFmpeg’s Theora decoder, than did I receive an email from the theora-dev list regarding the release of Theora 1.1.0. It took them many, many years to release the first official version and about 10 months to get the second version out, so congratulations on that matter. This release includes the much-vaunted Thusnelda encoder which is supposed to offer substantial encoding improvements vs. the original 1.0 encoder.

So, fair warning: Be prepared for a new round of “Theora Bests H.264 / HTML5 Video Poised To Conquer Internet” type of stories.

Since I have been doing a bunch of optimizations to the FFmpeg Theora decoder this past week (a.k.a. the Theora decoder that most people actually use), I thought this would be the perfect opportunity to benchmark Theora 1.1 alongside FFmpeg’s decoder. Fortunately, libtheora has an example tool called dump_video that decodes video directly to YUV4MPEG2 format, the same way I was testing FFmpeg’s decoder.

FFmpeg command line:

ffmpeg -threads n -i big_buck_bunny_1080p_stereo.ogg
  -f yuv4mpegpipe -an -y /dev/null

Libtheora command line:

dump_video big_buck_bunny_1080p_stereo.ogg > /dev/null

The results (on my Core 2 Duo Mac Mini) were thus:

6:44 - FFmpeg, 1 thread
6:09 - FFmpeg, 2 threads *
4:51 - libtheora 1.1

* multithreaded version isn’t complete yet

Mind you, libtheora’s decoder is singly-threaded and only has basic MMX SIMD optimizations. After seeing libtheora’s relative performance, I think I blacked out. Or maybe I just went to bed since it was so late; it’s sort of a blur. I awoke in a confused stupor wondering what I’m doing wrong in the FFmpeg Theora decoder. Why is it so slow? Actually, I know why– unpack_vlcs(), which continues to dominate profiling statistics. Perhaps the question I should start with is, how does libtheora unpack VLCs so quickly? That’s a good jumping-off point for a future investigation.