音频处理：采样率转换与适应性转换方法

size_t resample(const void* src_audio_data,
                                       const size_t src_channels,
                                       const size_t src_bit_per_sample,
                                       const size_t src_sample_rate,
                                       const size_t samples,
                                       void* out_audio_data,
                                       const size_t dist_channels,
                                       const size_t dist_bit_per_sample,
                                       const size_t dist_sample_rate) {
  size_t src_byte_count = samples * (src_bit_per_sample / 8) * src_channels;

  //目标和源一致,源返回.
  if (src_channels == dist_channels &&
      src_bit_per_sample == dist_bit_per_sample &&
      src_sample_rate == dist_sample_rate) {
    memcpy(out_audio_data, src_audio_data, src_byte_count);
    return src_byte_count;
  }

  //不支持插值采样,源返回
  if (src_sample_rate < dist_sample_rate ||
      src_bit_per_sample < dist_bit_per_sample ||
      src_channels < dist_channels) {
    memcpy(out_audio_data, src_audio_data, src_byte_count);
    return src_byte_count;
  }

  //不支持8位采样,源返回
  if (dist_bit_per_sample == 8) {
    memcpy(out_audio_data, src_audio_data, src_byte_count);