[alsa-devel] How to use "hw" or "plughw"?

Hi everbody

I have a beginner in this area, i have to develop an audio application to implement filter algorithms to reduce the noisy of an audio I have readed the alsa api, and i decided to partition into 3 threads mi application, one for read samples from an audio file, the second for filter de samples, and the third for playback the audio filtered using snd_pcm_writei, but i am confused about the use "hw" and "plughw" when open de audio device.

Some suggestion