为什么 SDL2 提供的缓冲区，对于音频样本，不够大？

Question

I use SDL2 to create sound with format:

freq = 32 * 1500;
format = AUDIO_F32SYS;
channels = 1;
samples = 1500;

I expect length parameter in my callback to be 6000 ( 1 * sizeof(float) * 1500 ) but it is 3000.

I've tried to decrease sample count, use 2 channels, but always provided buffer is as half big as needed.

This is how I open audio device:

SDL_AudioSpec want, have;
SDL_zero(want);
want.freq = 32 * 1500;
want.format = AUDIO_F32SYS;
want.channels = 1;
want.samples = 1500;
want.callback = ::PlayDing;
want.userdata = this;
m_Audio = SDL_OpenAudioDevice(nullptr, 0, &want, &have, SDL_AUDIO_ALLOW_ANY_CHANGE);
// want == have here

All fields of want and have are equal.

This problem started to happen after I switched from Ubuntu to Debian on the same laptop.

Answer 1

I had a wrong assumption that each time the callback gets called it should fill samples amount of audio data.

The number of samples that callback needs to provide should be calculated inside callback based on length / sizeof(float) .