Between Linux and Anime

Welcome to yet another episode of “Refusing to Just Use Windows (TM)” !

Yes that’s right. Despite the general ease with which most mkv’s play on Linux systems, I discovered a couple of mkv’s just the other day that simply wouldn’t – not on VLC, mplayer, ffplay, kaffeine – nothing. Even with every last available codec pack (and their grannies) installed. Well, the audio plays well enough – but I get no video. Blank. Zip. On the other hand I was told that the files play on a properly set up Windows machine. So what else is new :)

Of course, the thing about mkv’s is that it’s a wrapper format – different mkv’s can hold video/audio/subtitles that require vastly different codecs, so being able to play one mkv doesn’t guarantee that you’ll be able play the next. This case is a classic example of that little principle. So next step would be to find out what is the internal video format being used. Some probing with ffmpeg and mplayer on the command line reveals that the video’s codec id is “V_MS/VFW/FOURCC“, and is actually an flv4, which should be decodable on Linux. However playing the file results in one form of complaint or another in the way of “V_MS/VFW/FOURCC” not being recognized as a codec. The result: No video – only the audio track plays.

To cut a long story short, after clamping my teeth down on it and doing my requisite googling (yes, Refusing to Just Use Windows), I put the clues together and managed to find a not-too-difficult way to the bottom of the issue. The idea is to manually specify/force the video decoder to use, since the players are incapable of automatically finding the right one. None of my players appear to allow me to do this though, so I used ffmpeg to decode and reencode it into a nicer format instead:

ffmpeg -vcodec vp6f -i inputFile.mkv -b 20000k output.avi

The -vcodec vp6f part is the important bit here of course. This should decode that pesky mkv and spit out a much friendlier avi file that should easily play on mplayer, vlc or the like.

If your mkv has subtitles, you’ll need to do some extra stuff, since ffmpeg to the best of my knowledge does not play nice with subs. The above step should get you an avi with video and audio. To also add subs, you first need to extract them from the mkv. One way to do this is using mkvextract, which you should be able to install in your system by installing the “mkvtoolnix” package. mkvextract lets you extract a track from your mkv. The subtitle track is usually track 3, so you’d do something like:

mkvextract tracks file.mkv 3:output.subs

You can check which track your subtitles are on by doing ffprobe file.mkv. Once you have the subs extracted, you can simply direct your player to the extracted subtitles file and it should display. If you name your subtitles file after your avi file, some players would even automatically load it. All I needed to do was:

mplayer output.avi -ass

Of course, if you feel like it, you can also burn the subtitles into the video file itself. You can use mencoder for that, or you can use avidemux following instructions here

Hope that helps someone ;)

So last night I got pwned by zw as he demonstrated before mine disbelieving eyes this interesting feature he called audio boosting on his machine’s Windows Media Player classic. We were trying to watch this video with an unspeakably soft audio track, and after not being able to hear nuts when I played it on my Linuxbox + shoddy speakers, he smugly plugged the thing through his laptop’s Windows Media Player classic and turned on software audio amplification – and we did indeed get significantly more audible audio. Despite having (immense) issues with Media Player Classic’s UI/UX, I had to concede that that was an immensely handy feature. And so it was Windows 1:0 Linux that night.

But of course, while I do agree that Windows does certain things better than Linux, getting soundly beaten by the likes of Windows Media Player *Classic* is bound not to sit well with this user :P So having been enlightened to the existence of such a feature, I set off today to find out if it exists on Linux players. And it fortunately turns out that the answer is yes! On mplayer, all one needs to do is to add an extra argument. For example,

mplayer -af volume=20:0 mediafile

Would amplify the sound by 20dB. 20dB makes a HUGE difference by the way, so you might want to turn down your speakers/take off your headphones before you try it, in case you inadvertantly deafen yourself. So there you have it. Oh, apparently VLC has support for it too, but that’s beyond the scope of this post for now :)

Source

So after a good long time not being able to play this Facebook game we’re building for P2P-related research, which runs on Java Web Start, I finally got pissed today and sat down and finally got to the bottom of it.

Because Java isn’t free technology and all that, OpenSUSE actually comes preinstalled with OpenJDK instead of the common version of Java distributed by Sun. With this default configuration, Web Start (JNLP) files on the internet will open by default in an open implementation of Java Web Start called ‘IcedTea Web Start’, which I hear works reasonably well – but outright doesn’t work for some cases, like mine.

For people who, like me, need to run Sun’s version of Web Start from Firefox – first, you need to grab and install Sun’s version of the Java runtime using your software package manager (in OpenSUSE the package is called java-1_6_0-sun). Verify that you have a program called ‘javaws’ after this step. You can simply type ‘javaws’ into an open terminal and make sure it is recognized as Java(TM) Web Start.

Okay, next all we need to do is get Firefox to use javaws when opening JNLP files. For other distros you’d go to Edit > Preferences > Applications in Firefox, look for JNLP, and change the setting so it uses javaws. On OpenSUSE, Firefox is integrated so it takes its file-association settings directly from KDE. So you’ll have to instead go to KDE’s systemsettings (Configure Desktop) > Advanced Tab > File Associations. Here, run a search for JNLP, then add ‘/usr/bin/javaws’ to the top of the Application Preference Order.

We’re done! Next time you open a JNLP Web Start file in Firefox, it should offer to use Sun’s Java Web Start to open it :)

Damn, I’ve got so many things I should have written and posted but Chinese New Year stuff keeps getting in the way and unexpected problems keep cropping up. I just solved the latest one (unexpected problem), and I think this solution needs to be posted, so bear with me :)

If recordmydesktop gives you ridiculously slow frame-rate in it’s output video, you may be a victim of the “libtheora above v1.1.0” problem. Try the following for a quick-fix:

Add --v_bitrate 2000000 to the options you pass to recordmydesktop. If you use a frontend (like gtk-recordmydesktop or qt-recordmydesktop), look in your configuration for an “Extra Options” section and paste --v_bitrate 2000000 into it.

Worked like a charm for me. Source.