On Tue, Aug 18, 2015 at 12:01 AM, Anssi Hannula anssi.hannula@iki.fi wrote:
Hi,
17.08.2015, 17:16, Takashi Iwai kirjoitti:
On Sun, 16 Aug 2015 14:50:12 +0200, Anssi Hannula wrote:
AudioQuest DragonFly DAC reports a volume control range of 0..50 (0x0000..0x0032) which in USB Audio means a range of 0 .. 0.2dB, which is obviously incorrect and causes software using the dB information in e.g. volume sliders to have a massive volume difference in 100..102% range.
The actual volume mapping seems to be neither linear volume nor linear dB scale, but instead quite close to the cubic mapping e.g. alsamixer uses, with a range of -53...0 dB.
Add a quirk for DragonFly to use a custom dB mapping, based on my measurements, using a 10-item range TLV (so it still fits in alsa-lib MAX_TLV_RANGE_SIZE).
Tested on AudioQuest DragonFly HW v1.2. The quirk is only applied if the range is 0..50, so if this gets fixed/changed in later HW revisions it will no longer be applied.
Signed-off-by: Anssi Hannula anssi.hannula@iki.fi Cc: stable@vger.kernel.org
sound/usb/mixer_quirks.c | 37 +++++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+)
diff --git a/sound/usb/mixer_quirks.c b/sound/usb/mixer_quirks.c index 337c317ead6f..39d7f34e44e6 100644 --- a/sound/usb/mixer_quirks.c +++ b/sound/usb/mixer_quirks.c @@ -37,6 +37,7 @@ #include <sound/control.h> #include <sound/hwdep.h> #include <sound/info.h> +#include <sound/tlv.h>
#include "usbaudio.h" #include "mixer.h" @@ -1733,6 +1734,38 @@ static int snd_microii_controls_create(struct
usb_mixer_interface *mixer)
return 0;}
+static void snd_dragonfly_quirk_db_scale(struct usb_mixer_interface
*mixer)
+{
- struct usb_mixer_elem_list *list;
- struct usb_mixer_elem_info *cval;
- static const int unit_id = 7;
- /* approximation using 10 ranges based on output measurement on hw
v1.2 */
- static const DECLARE_TLV_DB_RANGE(scale,
0, 1, TLV_DB_MINMAX_ITEM(-5300, -4970),2, 5, TLV_DB_MINMAX_ITEM(-4710, -4160),6, 7, TLV_DB_MINMAX_ITEM(-3884, -3710),8, 14, TLV_DB_MINMAX_ITEM(-3443, -2560),15, 16, TLV_DB_MINMAX_ITEM(-2475, -2324),17, 19, TLV_DB_MINMAX_ITEM(-2228, -2031),20, 26, TLV_DB_MINMAX_ITEM(-1910, -1393),27, 31, TLV_DB_MINMAX_ITEM(-1322, -1032),32, 40, TLV_DB_MINMAX_ITEM(-968, -490),41, 50, TLV_DB_MINMAX_ITEM(-441, 0),- );
- for (list = mixer->id_elems[unit_id]; list; list =
list->next_id_elem) {
cval = (struct usb_mixer_elem_info *)list;if (cval->control == UAC_FU_VOLUME &&cval->min == 0 && cval->max == 50) {usb_audio_info(mixer->chip, "applying DragonFly dBscale quirk\n");
list->kctl->tlv.p = scale;list->kctl->vd[0].access |=SNDRV_CTL_ELEM_ACCESS_TLV_READ;
list->kctl->vd[0].access &=~SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK;
}- }
Instead of looking through the list, just hooking at build_feature_ctl() would be simpler in the end, I think. E.g. something like:
--- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -1334,6 +1334,7 @@ static void build_feature_ctl(struct mixer_build
*state, void *raw_desc,
SNDRV_CTL_ELEM_ACCESS_TLV_READ | SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK; }
mixer_fu_apply_quirk(state->mixer, cval, unitid, kctl); } range = (cval->max - cval->min) / cval->res;... and the quirk implementation in mixer_quirks.c like
static void snd_dragonfly_quirk_db_scale(mixer, kctl) { usb_audio_info(mixer->chip, "applying DragonFly dB scale quirk\n"); kctl->tlv.p = scale; kctl->vd[0].access |= SNDRV_CTL_ELEM_ACCESS_TLV_READ; list->kctl->vd[0].access &= ~SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK; }
void mixer_fu_apply_quirk(mixer, cval, unitid, kctl) { switch (mixer->chip->usb_id) { case USB_ID(0x21b4, 0x0081): /* AudioQuest DragonFly */ if (unitid == 7 && cval->min == 0 && cval->max == 50) snd_dragonfly_quirk_db_scale(mixer, kctl); break; } }
OK, seems like a good idea.
However, I just noticed another volume quirk for DragonFly has already been merged since I started looking into this:
https://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/commit/?id=2d1c...
It sets a fixed dB linear range map of 0...50dB via mixer_maps.c, which doesn't seem 100% right to me. While it is much better than the unquirked 0...0.2dB, it causes e.g. pulseaudio mixer to show the nearly inaudible raw 0 as the "base" level. And, unless I made some silly mistake, the volume scale is not actually linear dB AFAICS.
Yao-Wen, did you have some basis for the assumption "dB conversion factor is 1" on DragonFly other than that it sounded approximately right?
No. I used this assumption because I didn't have a good measuring instrument. You can just remove my quirk and use yours. Thanks!
Takashi, should I add removal of that "duplicate" quirk in the same commit (or a separate one)? (assuming my quirk turns out to be actually better/correct, of course)
-- Anssi Hannula