Author Archives: Multimedia Mike

FATE Testers Wanted

This evening, I finally got my fate-client.py script minimally ready for general consumption. fate-client.py is the unimaginatively named program I threw together some time ago to allow me to validate test specs before I activate them so that FATE will automatically test them. It works like this:

  • download the script (http://fate.multimedia.cx/fate-client.py)
  • rsync the FATE suite of samples that live on mphq: ‘rsync -aL rsync://rsync.mplayerhq.hu:/samples/fate-suite/ samples’ (without the quotes, of course) — this presently amounts to ~150 MB
  • build FFmpeg as normal
  • ‘./fate-client.py -f </path/to/ffmpeg-binary> -s </path/to/fate-suite/samples>’

That’s it. The script will ask the FATE server for a set of test specifications and run through them. You may also need to specify -l/–libpath= if you built and installed FFmpeg with shared libraries. Naturally, ‘./fate-client.py -h’ will spell out all the options.

You would do well to make sure that all the options are valid or else suffer Python bailout exceptions. I just added the command line options tonight and have not made them very resilient. I have been promising this utility for a long time and I wanted to get something out there sooner than later.

Remember that I’m still a rank amateur at Python, so don’t be afraid to call me out if I’m doing anything in the worst Pythonic way imaginable.

Ideas for future improvement:

  • Better logging– Instead of dumping to stdout, maybe dump all the results to a CSV file (for spreadsheet analysis) and/or an HTML file for easy viewing
  • Proper versioning– I track the script via a local git repository, but how do I communicate the current version? Would this be version dd394ef8f3dad056c39ab4e1c76951190621cf8b?
  • Robust error handling
  • Range testing (run all tests up to ID n, or run all tests after ID n, or from IDs m to n)
  • Skip a list of tests (for example, it would be useful to skip test #128 — the internal FFmpeg regression test — since it’s not that helpful in this particular scenario)
  • [Your idea here]

It’s open source, GPL v2, so patches welcome. Moreover, I would love to hear if this script works at all for anyone else. Then, I would like to hear how it works on platforms outside of the 3 that FATE now rigorously tests– I speak of Mac OS X, *BSD, Win32 with either MSVC or MinGW, Open/Solaris on all its various platforms, even PlayStation 3 and whatever else. I actually did get that OpenSolaris VMware session to boot after I waited long enough but I had no idea how to do anything useful with it. That’s when I decided to get down to it and get this script out there so that hopefully someone else will test those platforms.

Extra credit: Figure out why, when bailing out of the test sequence early with Ctrl-C, terminal character echo is off. I.e., the terminal refuses to print keystrokes.

Alternate Subtitles

Kostya recently lamented the matter of subtitle quality. I admit that subtitles are not a topic that I have traditionally cared very deeply about, popular though they may be in the multimedia scene. All the media I care about is generally already in English. Apparently, I’m one of the rare geeks who absolutely detests anime, so I have no reason to care about fansubs for media “imported,” one way or another, from certain Pacific islands.

However, some time ago, I suddenly found a reason to care about subtitles. It turns out that subtitles don’t have to contain bad translations. I’m a huge fan of the old TV show Mystery Science Theater 3000 (a.k.a. MST3K). In a nutshell, the silhouettes of a guy and his 2 robot puppets make fun of rotten movies. They crack an incredibly wide variety of jokes and it’s unlikely anyone can understand every one of them. Leave it to a collaboration of internet geeks to develop an annotation project where users can submit quotes and annotations corresponding to particular timecodes in the lousy movies. These annotations go into a database where they can be downloaded as plaintext .srt subtitle files.


VLC playing MST3K 0904 (Werewolf) with subtitle annotations

“Now what we’re doin’ here, Bob, is gettin’ killed by a werewolf.”

Pictured is an annotation I added for episode 0904 – Werewolf. This is nothing new in the context of DVDs — I remember watching a popup trivia subtitle track on the Spider-Man DVD. But I’m wondering if there are other annotation projects like this one out there on the net for other niche areas of interest.

Libsndfile Survey; CAFF

I have been sitting on the results of this little experiment for a month now. I was in a bit more of a hurry during the qualification period for this year’s Summer of Code because I knew it would eventually yield a bumper crop of suitable qualification tasks. But that time has long passed.

The task at hand is to systematically survey the types of files that libsndfile can create, see what it can do that FFmpeg can’t, and make a plan to get those formats into FFmpeg starting with listing them as small tasks.

Libsndfile comes with several small example utilities (something can FFmpeg could probably use instead of, or to supplement, one big utility). One such program is sndfile-convert

I had to modify sndfile-convert since not all of the supported formats were enumerated in its case-switch statements. The result of the above command was 120 unique format/codec combinations. I have uploaded all 120 cow moo samples (taken from the OpenOffice media suite, handy on my Eee PC when I was running this experiment).

How many of these 120 files can FFmpeg decode? I compiled FFmpeg with GSM 6.10 support and used the following command to print out FFmpeg return code and filename for each sample:

for file in `ls`; do
  ffmpeg -i $file -f wav - 1> /dev/null 2> /dev/null;
  echo $? $file; 
done

The count is: 26 supported, 94 unsupported. Time to get to work. You wouldn’t believe how many different ways there are to wrap raw PCM data with a basic file header for storage and transport.

Actually, closer inspection will reveal that FFmpeg is not necessarily ready to support all of these file formats since a number of them contain 24- or 32-bit integer PCM, or 32- or 64-bit floating point PCM; these are longstanding FFmpeg TODO items.

Libsndfile is actually the first program I have encountered that handles Apple Core Audio Format Files (CAF or CAFF). I haven’t even found an Apple program that creates these, at least not among the offerings bundled with Mac OS X 10.5. Now that I have created some CAFs, I see that Apple’s QuickTime Player plays them handily.

FFmpeg also doesn’t support multichannel (more-than-stereo) audio very robustly in its present incarnation. Yeah, that’s another item on the TODO list. Check out the complete specs for CAFF, however. I think if we made it a goal to support CAFF to its fullest (save perhaps for its pulse-width modulation provisions), FFmpeg’s audio handling would reign supreme at the end of the journey.

For the curious, these are the 26/120 files that FFmpeg can decode at this time:

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