This function takes two audio buffers of len bytes each +of the playing audio format and mixes them, performing addition, volume +adjustment, and overflow clipping. The volume ranges +from 0 to SDL_MIX_MAXVOLUME and should be set to the maximum +value for full audio volume. Note this does not change hardware volume. This is +provided for convenience -- you can mix your own audio data.
Note: Do not use this function for mixing together more than two streams of sample +data. The output from repeated application of this function may be distorted +by clipping, because there is no accumulator with greater range than the +input (not to mention this being an inefficient way of doing it). +Use mixing functions from SDL_mixer, OpenAL, or write your own mixer instead.