A week ago, I was curious about the features of the Advanced SubStation Alpha (SSA v4+) subtitle format. I tried typesetting the April 15, 2007, episode of Haromoni@ and found them to be pretty nice compared to an unstyled SubRip render. I set out to find a renderer that would display them nicely and properly.
I decided to compare VSFilter, libass, and the internal VLC subtitle renderer. The following were used in the tests (also the order of the images).
- VSFilter 2.37 (or DirectVobSub) with Media Player Classic 6.4.9.0 (2007-03-25 build)
- MPlayer CCCP-SVN-r21703-3.4.5 (libass internal) with SMPlayer 0.3.42
- VLC media player 0.8.6b (internal)
The first test was to see if the subtitles were actually recognized. With VSFilter, the subtitles were loaded automatically, with the text being styled correctly. libass seemed to have passed the test as well with everything looking near VSFilter’s render. The only difference was the the ten percent text size decrease. VLC failed to automatically load the subtitle file. I loaded the file manually, but it did not render any type of text. After letting it play for a second, it appeared to have skipped right over the first two lines of dialogue.
Test two tried the renderer with two overlapping lines of text appearing during the same interval. VSFilter properly displayed the two lines with the correct border and placement. libass did the same by recognizing all the colored borders. VLC flopped again recognizing neither the colors nor the position of the lines. The lines run right over each other, creating a jumble of unreadable words. VLC did, though, take into account the font size.
The final check was to compare the “opaque box” box border. Using the VSFilter render as the reference image, libass does not draw the box around the text but did get the border color correct. VLC took only the font size, and that’s about it.
VSFilter seems to have won this quick battle. It rendered every line meeting expectations. I was also quite impressed with the development of MPlayer’s libass. It’s near accurate renderings compare quite well with VSFilter’s. It only has the oddness of having a slightly smaller font size and did not recognize the box border style. VLC did not pass any of the tests. It displayed horrible word wrapping issues and did not want to conform to any styles besides the font size.