I've promised that I'll dig into some old file formats and check how well they can be accessed on today's systems with free software.
Today, I'll start with audio formats. To begin, in general there are two kinds of audio formats. Streamed audio formats start with a more or less raw audio stream, apply some encoding and sometimes (lossless or lossy) compression. There are also tracker audio formats. They have internal information on tone pitches and instruments. Most really old computer audio files are tracker formats (like the popular C64 SID format). This blog post will be about streamed audio formats and I'll save the tracked ones for a later one.
The file formats I've chosen are more or less random, the main criteria being that I once stepped over them and still remember that. There's a hughe collection of all kinds of
media file samples on the mplayer server.
The single most important project regarding exotic audio or video formats is
ffmpeg, a library that does despite its name much more than decoding mpeg. All major free software media players use ffmpeg.
The file formats I've investigated:
- Some of the very first files distributing music through the Internet I remember were real audio files (extension .ra or .rm) from the german punk band WIZO. Real audio has a whole bunch of variants, scanning through some of my old backups, most of them used either AC-3 or Real Audio 2.0 as their codec. Thanks to Waybach Machine, you can still find the WIZO downloads (Raum der Zeit - Techno is AC-3, the others are RealAudio 2.0).
- vqf (or TwinVQ) was once announced having better quality than MP3 and was discussed as its successor. However, it seems it is almost completely distinct today, I didn't find anything at all (except in the above mentioned sample collection) in vqf format for download.
- Monkey's audio, extension .ape, is a lossless audio codec, which is itself licensed under some kind of noncommercial-use-only license that doesn't qualify as free software. It's not really old, as it's still being developed, but I added it as another example of an uncommon format.
- Shorten (extension shn) is an old lossless audio format, which was often used by the etree project that collects recordings of concerts. Today, it is mostly deprecated by flac, but the old recordings are still available.
- voc: The popular dos floppy copying program vgacopy had sound before I had a soundcard - it used the pc speaker to play .voc files it had shipped. It's a format used by some Creative software for their SoundBlaster. It's a more-or-less raw audio format like wav.
ffmpeg is able to decode and play all of these audio codecs. But what I found out was that this doesn't necessarily mean every application using ffmpeg can do this as well. I've tested
mplayer,
xine,
vlc,
audacious and
totem (based on
gstreamer). Although there are quite many free software media players - both for audio and video - out there, this should cover pretty much everything. Most media players use xine, vlc or gstreamer indirectly.
| | mplayer | xine | vlc | audacious | totem/gstreamer |
| ra AC3 | Yes | No Yes | Yes | Yes | No |
| ra 2.0 | Yes | No | No | Yes | No |
| vqf | Yes | No | Yes | Yes | No |
| ape | Yes | No | No | Yes | Yes |
| shn | Yes | Yes | No | Yes | Yes |
| voc | Yes | Scratchy | Scratchy | No | No |
Shorten playback has some problems, seeking often does not work, but this seems to be a limitation of the format itself. If I found feature requests for those formats, I've linked them, I also opened a bunch of them myself.
Conclusion: ffmpeg does a really fine job in playing all the obscure audio streaming formats. However, not every player that's based on ffmpeg plays every format ffmpeg can play. mplayer is the only player that succeeds with everything, probably because mplayer's devleopment is very tightly related to ffmpeg's development.
Update: I forgot to mention
libav. It is a fork of ffmpeg. However, there's not that much to say, as ffmpeg and libav are still quite similar in their codec support. audacious does not support libav yet, all other apps just produce the same result.
