ALSA Music/MIDI Driver

[bernhard84]

Hi!

I just wrote a MIDI music driver for ALSA (Linux). A patch for openttd 0.7.1 is attached below...

As a SoundBlaster Live user I was never really happy about the way MIDI music was handled in the Linux version of OpenTTD. Actually my sound hardware is capable of producing high-quality MIDI sound, but it's hard/impossible to use it in OpenTTD. The only options for me so far were:

• using timidity, a software synth which consumes lots of CPU but still sounds inferior than my wavetable sound card
• using extmidi, an ugly hack which didn't work for me for some reason

Well, since Transport Tycoon is only half the fun without the music, I decided to write a "native music driver" for ALSA. It's the most complex music driver so far, because it has to handle "everything" (reading and parsing MIDI files, sending MIDI events, managing playback thread, selecting a suitable output port, etc) on its own. ALSA is really a programmer's nightmare...
But finally I can enjoy the music without the horrors of timidity or extmidi now. Hooray!

Needless to say, I'd love to see this driver being included in one of the next releases...


Cheers,
Bernhard

[Ammler]

Needless to say, I'd love to see this driver being included in one of the next releases...

Then you should patch trunk.

Greets
Ammler

[bernhard84]

Then you should patch trunk.

Hmm... interesting idea. If someone gives me a subversion account, I'll do it!
I just hope that nobody's gonna kill me if my code deletes your hard disk, tortures your kitten, sets your house on fire, ...

[Terkhen]

Ammler means that, if you are looking forward to inclusion, you should create your patches against latest trunk version, not against stable versions. Only devs can commit code to trunk.

[bernhard84]

And I thought:
Wow, that's an OPEN source project! They just want ANYONE to commit on trunk!

OK, here's my patch against trunk.

[Roujin]

And I thought:
Wow, that's an OPEN source project! They just want ANYONE to commit on trunk!

OK, here's my patch against trunk.

Haha, that would be too chaotic.. Actually the devs here are checking patches quite thoroughly before considering to put them in trunk.
You may also want to create a flyspray task (category Patch). There it's more likely to get a dev's attention.

[TrueBrain]

Impressive.

One comment I have: please try to follow the coding style of OpenTTD. It is pretty important if you are serious about your patch Examples:

not 'void* ', but 'void *'
'//' to make a comment on the same line code is on
unneeded white lines

stuff like that

[peter1138]

I can't really see the point of adding all the complexity of a MIDI file parser just for one output driver, when using extmidi, along with pmidi, works perfectly well.

Some other comments, ignoring code style:
* There's a complete byte-oriented file reader in there. We have one of those already.
* It's pretty impossible to auto-detect which ALSA port to use, and get it correct. pmidi's method works well; that is use either the explicitly supplied port (the driver system does support parameters) or use ALSA_OUTPUT_PORTS. It never auto-detects.

[bernhard84]

OK, I updated the patch (see my previous posting).

Changes: fixed reading ALSA_OUTPUT_PORTS environment variable, refined auto-detection (also detects fluidsynth and timidity now), try to comply with OpenTTD coding standard (probably still not perfect yet).

There's a complete byte-oriented file reader in there. We have one of those already.

OK, I'll have a look at it later.

It's pretty impossible to auto-detect which ALSA port to use, and get it correct. pmidi's method works well; that is use either the explicitly supplied port (the driver system does support parameters) or use ALSA_OUTPUT_PORTS. It never auto-detects.

Well, probably it's impossible to get auto-detection right in 100% of all possible cases. But that's not the aim of it anyway. It should work for most people and in most common hardware/software setups. It's good enough if it's correct in 90 out of 100 cases.
I think that most ordinary users don't want to check their ALSA configuration before launching openttd. That's what auto-detection is designed for - just launching openttd without having to specify any extra parameters. People who want to have full control over the music output can set ALSA_OUTPUT_PORTS.

[id10terror]

I can name a good reason to keep a working midi file reader around. It might be nessary in the future, if i rembember correctly ms has discontinued directmusic. Or if you wanted to move away from directmusic on winxx systems and say toward somthing more open source, it might be quite beneficial.

[peter1138]

Hmm, I wonder how it would look if the file parser part was split off from the main output driver by using an intermediate class?

* MusicDriver_ALSA > MusicDriver_MIDIFile > MusicDriver
* MusicDriver_... > MusicDriver_MIDIFile > MusicDriver

[bernhard84]

Hmm, I wonder how it would look if the file parser part was split off from the main output driver by using an intermediate class?
* MusicDriver_ALSA > MusicDriver_MIDIFile > MusicDriver
* MusicDriver_... > MusicDriver_MIDIFile > MusicDriver

Actually not a bad idea. I think I'll implement something like that when I have some time... But it's not gonna be as simple as it seems, because the MIDI parser itself uses ALSA data structures, and I have to get rid of this ALSA dependency somehow.