Playing Sounds Without Allocations

[pfirsich]

Hello,

I am trying to implement an API for a game roughly like this using miniaudio:

sound_init(size_t max_num_sound_sources, size_t max_num_sounds);
sound_source_id sound_source_load(const char* path, bool stream);
sound_id sound_play(sound_source_id src, sound_play_params params_ignore);

where sound_source_load would front-load all IO/decoding and sound_play should play a sound without doing any allocations. I really want to avoid doing memory allocations in the game's main loop.

I am not sure how to do this best. It seems to me that every version of ma_sound_init will allocate at least in ma_engine_node_init (pHeap). And it also seems like you cannot change the data source of an existing sound, once it has been initialized, so the only options I see are:

• Pre-allocate and init a number of ma_sound for each sound source, i.e. don't have a max_num_sounds, but a max_num_sounds PER sound source.
• Specify a custom allocator, set a flag just before initializing a sound and redirecting the allocations to a buffer that is kept alongside the sounds. I think this is a bit ugly and also I don't know the allocation sizes beforehand.

What way would you recommend to implement an API like this or more generally use miniaudio to play sounds without allocating in the main loop? Is there a way to provide the additional heap memory needed by a sound node from the outside and somehow query the needed memory beforehand?

[mackron]

Unfortunately you're out of luck with this one. The most practical way would be custom allocation callbacks, but like you alluded to, that's quite generic and it won't give you intelligence as to what specifically is being allocated. But to optimize your allocations as much as possible, a custom allocator is the best option I can think of.

I have some distant plans to change the high level API to make ma_sound management less error prone (messing this up is easily the most common mistake people make with miniaudio). I also want to improve some other things I don't like. I could possibly look at improving the memory allocation situation when I get to that, but that's literally years out from now and not practical to think about as of this moment. Just thinking out loud here, but you might have noticed functions like ma_engine_node_init_preallocated() - I could possibly do something like ma_sound_init_preallocated(). Would need to think about it.

[pfirsich]

Hey! Thanks for the quick reply. I did notice the _preallocated functions and I wished those existed for sounds too! I assume you will provide a ma_sound_get_heap_size/ma_sound_init_preallocated pair for the sound? That would be more than enough and make a lot of sense in the context of the rest of the library imho. Until then I'll just put a hacky flag in my allocator or add that function myself.
Thanks a lot for miniaudio. There are not many good audio libraries and I think you did a lot of things right with miniaudio, as far as I (a non-audio person) can tell.

This is not entirely related, but I think it might be useful to add an example that shows how to play SFX in a game, i.e. load a couple of sounds from files and then play a number of them (including multiple simultaneous instances of some of the sounds). Because miniaudio provides many ways to do something like this and I find it difficult to determine the best one. I realize ma_engine_play_sound might be an example (i.e. keep a list of ma_sounds, recycle them and ma_sound_uninit/ma_sound_init_from_file every time you want to play a sound), but would that be the the way you recommend games do it? Or should I load a single sound and ma_sound_init_copy it and play the copies? Or should I init a data source with the resource manager and init sounds from that? I feel like many people will probably use miniaudio for games and it's not entirely clear to me how to use it best for that. I.e. I haven't really played any sounds yet, but read quite a bit of code and thought about it a lot and I think an example that says how to use miniaudio for games would have helped.

[mackron]

I assume you will provide a ma_sound_get_heap_size/ma_sound_init_preallocated pair for the sound?

That was my initial thought off the top of my head, yeah. I haven't thought about it thoroughly, but it makes sense from a consistency point of view.

I think it might be useful to add an example that shows how to play SFX in a game

This has been asked before, and yes I agree. Just haven't had a chance to sit down and write up an example just yet. I actually want to make a little game to demonstrate some real-world use cases. But as usual, no time.

You almost certainly don't want to be using ma_engine_play_sound() for serious stuff, but it can still be useful for people who just want some simple fire-and-forget sounds without any spatialization or effects. I just use that in examples to keep it short, but I kind of wonder if I should stop using it there.

Or should I load a single sound and ma_sound_init_copy it and play the copies?

This is what I'd recommend. Just note that it will not work with MA_SOUND_FLAG_STREAM, nor will it work with ma_sound_init_from_data_source().