CAPTURE_P16V_SOURCE
snd_emu10k1_ptr20_write(emu, CAPTURE_P16V_SOURCE, 0, 0x78e4);
tmp = snd_emu10k1_ptr20_read(emu, CAPTURE_P16V_SOURCE, 0) & 0xfffc;
snd_emu10k1_ptr20_write(emu, CAPTURE_P16V_SOURCE, 0, tmp | val);