函数 av_audio_fifo_alloc 

pub unsafe extern "C" fn av_audio_fifo_alloc(
    sample_fmt: AVSampleFormat,
    channels: c_int,
    nb_samples: c_int,
) -> *mut AVAudioFifo

Allocate an AVAudioFifo.

@param sample_fmt sample format @param channels number of channels @param nb_samples initial allocation size, in samples @return newly allocated AVAudioFifo, or NULL on error