这个函数里面的语句怎么理解？

famework里面的Media， IMediaRecorder.cpp
谢谢status_t setAudioSource(int as)
    {
        LOGV("setAudioSource(%d)", as);
        Parcel data, reply;
        data.writeInterfaceToken(IMediaRecorder::getInterfaceDescriptor());
        data.writeInt32(as);
        remote()->transact(SET_AUDIO_SOURCE, data, &reply);
        return reply.readInt32();
    }