audio_fill_sil
audio_fill_sil(sc, sc->play.data, sc->play.klen);
audio_fill_sil(sc, sc->rec.data, sc->rec.klen);
audio_fill_sil(sc, ptr, count);
audio_fill_sil(sc, sc->play.data, sc->play.klen);
audio_fill_sil(sc, sc->rec.data, sc->rec.klen);
audio_fill_sil(sc, sc->play.data + sc->play.start,
audio_fill_sil(sc, ptr, sc->rec.blksz);