yeah nothing like that
Here's an edited irc log with P about it as I think the same questions will come up (I hope P doesn't mind
). The top bit is all you need.
[22:51] <P__> you want to play 15000 sounds a sec ?
[22:52] <Vectrex> hehe, yep
[22:52] <P__> the problem is that the internal refresh rate of openAL is to 40Hz if i remember correctly
[22:52] <Vectrex> basically so it sythesises like a real engine
[22:52] <P__> i'm not sure about how it works internally, but i'm almost sure you will run into precision issues
[22:53] <P__> you could just record at several rpm, and blend that with piching, that's what most game do, ok not as fun as what you want, but works ;Ã
[22:53] <Vectrex> heh yeah that's what we've done now
[22:53] <Vectrex> works ok, but not good enough
[22:53] <Vectrex> I know you can do it, I'll have to run another thread though I think
[22:54] <P__> i don't think it's possible to spawn 15000 sounds a sec, just because they will overlap, and the max simultaneous sources available will be quickly overtaken
[22:54] <Vectrex> nah, nothing like that. I'm simulating a one cylinder engine, so they can cut each other off
[23:02] <Vectrex> ok here is a recording of a real kart
[23:03] <Vectrex> we straped 2 microphones to the artist who is a karter
[23:03] <Vectrex>
http://users.on.net/~edan/games/KartSimulator/visible/
[23:03] <Vectrex> play the 'zac real kart lap' mp3 first
[23:03] <P__> ok
[23:05] <Vectrex> so with the synth version I'm only using one cylinder sample, so it sounds bad down low, but we'll sample lots of varations
[23:06] <Vectrex> and we also need to do some filtering of the engine sound, so another thing i have no idea how to do
[23:06] <P__> downloading the second sound now
[23:07] <P__> it sounds like a bee
[23:07] <P__> if it's the right word
[23:07] <P__> a bad mood one !
[23:07] <Vectrex> hehe yeah, the little buggers rev at like 16,000 rpm
[23:07] <Vectrex> with no gears
[23:08] <Vectrex> so that's a mockup in this music program I use
[23:08] <P__> filtering in which sense ?
[23:08] <Vectrex> when you decellerate a value closes and muffles the firing sound
[23:09] <P__> ok
[23:09] <P__> i think it can be done 2 ways, by applying a filter like the one presents in openAL EFX extension, or by making the filter yourself
[23:10] <Vectrex> well we have filter code used for realtime apps (flatmate
[23:10] <P__> the seonc is more tricky maybe, because you need to divide the sound in several buffers like if you were streaming it
[23:10] <P__> hehe
[23:10] <P__> sounds a lot of experimenting and fun
[23:10] <Vectrex> can't I run this in another thread and pass basic info to it from the main thread?
[23:11] <P__> you will not be able to modify a buffer while it's playing, by design
[23:11] <Vectrex> so just as my music program is simulating it running at 15,000 a sec only using 2% cpu?
[23:11] <P__> i can be wrong but that how i understand it
[23:11] <Vectrex> no that's what I want
[23:11] <Vectrex> each fire sound it unique, I don't actually change the pitch at all in the mockup
[23:11] <Vectrex> like a real engine
[23:12] <Vectrex> the pitch is coming from the fact that it's being fired so many times a second
[23:12] <P__> yes i understand
[23:12] <P__> the second thread would then control the firing isn't it ?
[23:12] <Vectrex> so basically I can pass the current engine rpm from the main thread to the audio one and change the rate there
[23:12] <P__> playing the sound i mean
[23:12] <Vectrex> yeah
[23:12] <P__> yes that would be possible i think
[23:13] <P__> as long as all the audio stuff is done in the second thread
[23:13] <Vectrex> yep
[23:13] <Vectrex> only basic low rate info would be passed one way to the audio thread
[23:13] <Vectrex> like acceleration amount, current rpm etc
[23:13] <P__> but why not using loop at diferent rpm, won't the effect be the same ? unless you change the pitch at a very high frequency, which mean that the game has to be updated at very high freq
[23:14] <Vectrex> the audio thread would then do a little bit of interpolation between values to avoid low framerate jumping of the frequency
[23:14] <Vectrex> well the thing with that is the pitch shifting sounds totally wrong
[23:14] <Vectrex> engines don't change the pitch, they change the firing rate
[23:15] <Vectrex> so I play the samples at the originally recorded pitch
[23:15] <P__> yes it's not exact
[23:15] <Vectrex> plus a big bonus is I can pass engine damage parameters to the audio thread, to subtly change the timing
[23:15] <P__> it modifies the sound freq
[23:15] <Vectrex> for tuning the engine
[23:16] <Vectrex> yeah, we do it the 'normal' way now and it works, but it's really not that great
[23:16] <P__> how many loops ?
[23:16] <Vectrex> 6
[23:16] <P__> maybe that's the point and it should be increased to 20, i don't know
[23:17] <P__> i don't say you are wrong with what you want to try at all, just that sounds a bit overkill
[23:17] <Vectrex> yeah, but it's very very hard to match up the samples with rate and pitch when fading
[23:17] <Vectrex> we'll have to put it on a bench and record exact rpms
[23:17] <Vectrex> otherwise it sounds like multiple karts like it does now
[23:18] <Vectrex> if we could match it up nicely then yeah more levels would work
[23:18] <P__> can't you find the rpm with your audio software, and then scale it as needed ?
[23:18] <Vectrex> yep, but it will always never quite match up, because engines aren't that stable
[23:18] <P__> to make it match perfectly, well i guess the rpm isn't something perfect constant
[23:18] <Vectrex> so it always sounds like there's 2 karts
[23:18] <P__> ok same understanding
[23:19] <Vectrex> it's easier with cars because they rev so low
[23:19] <Vectrex> or indeed tractors ;P
[23:19] <P__> i haven't work with the sound on this project, the other dev did, but we don't even have several loops
[23:20] <P__> so i'm just guessing on this point, never tried it
[23:20] <Vectrex> hehe, I've never seen a tractor go that fast
[23:29] <Vectrex> check this out
[23:29] <Vectrex>
http://www.youtube.com/watch?v=OdSPHFqplfA
[23:29] <Vectrex> richard burns rally
[23:29] <Vectrex> THE hardest/most realistic car get ever
[23:29] <Vectrex> this uses the synth engine idea
[23:30] <P__> far from toca3
[23:31] <Vectrex> haha just a bit