diff mbox

hda-codec: use smaller dynamic range for input amplifier

Message ID D4F4479A3531074699A555716DB7F84A9D966E9543@ABGEX71E.FSC.NET
State New
Headers show

Commit Message

Martin Wilck April 22, 2015, 8:01 a.m. UTC 
> > > The "right" solution for this problem would be to implement
> > > proper dB scaling in QEMU and the audio backends (such as spice).
> 
> Can we try this please?

I would like to, but it's a rather big project and beyond my current
QEMU progamming skills. Support seems to be lacking in the generic QEMU
audio layer.

> > > While this clean solution is not available, I suggest to decrease
> > > the dynamic range for the the emulated Amps in the QEMU hda codec.
> > > Experiments showed that with 32dB dynamic range with a 0.5 dB step,
> > > it was possible to set gain values as low as 5 (-29.5dB / 8%).
> > > Actual HW seems to use similar ranges for input amplifiers.
> 
> > I am afraid guest OS won't like it the card description changes after a migration.
> > This will likely need a new VMState field, for the steps, or the amp caps.
> 
> Correct.  This is a guest-visible change, so we have to make this
> runtime-switchable for compatibility with older qemu versions.  This
> quickly becomes a bit messy, so I'd prefer to avoid this.

So what do you suggest? The current situation (not being able to control
volume properly from the guest) is messy and should be fixed. It might
look like a minor problem, but try to run a Windows application that
attempts to auto-regulate input volume (such as Microsoft Lync/Skype) -
it simply doesn't work.

In the case of migration, what has to be avoided is that the guest
attempts to set a gain value outside the allowed range. So I should
modify my patch to use the same number of steps as before (0x4a).
Modified patch is attached.

Now, if the guest migrates from "new" to "old", it will continue to
assume a 0.5dB stepping. Because the HD audio step size is a purely
virtual value (we are not using dB at the moment), this will have the
effect that volume control after migration still behaves well. Likewise,
migrating from "old" to "new" will cause my fix not to become effective
in the "new" environment, because the guest will still assume 1dB
stepping.

Other than that, I can't see what might go wrong during a migration -
but maybe I am overlooking something? I have no environment to test
migration, so my thoughts above are just theoretical.

Martin
diff mbox

Patch

From bc4bbc4a92a8e9fb87aab1641f3868f7345b9b1e Mon Sep 17 00:00:00 2001
From: Martin Wilck <martin.wilck@ts.fujitsu.com>
Date: Tue, 21 Apr 2015 17:55:38 +0200
Subject: [PATCH] hda-codec: use smaller dynamic range for input amplifier

This patch addresses the following problem:

Moving the input volume slider 0% to 1% in a Win7 guest causes the
the "gain" values in the emulated HDA codec HW to jump from 0 to 40.
This makes it impossible to control sound volume in the low-gain
range using the windows guest.
This is related to how the Windows HDA codec driver and the QEMU
emulated HW interact. It seems that Windows uses a ~30dB overall
scale for the min-max range of the input volume slider.

The "right" solution for this problem would be to implement
proper dB scaling in QEMU and the audio backends (such as spice).

While this clean solution is not available, I suggest to decrease
the dynamic range for the the emulated Amps in the QEMU hda codec.
Experiments showed that with 32dB dynamic range with a 0.5 dB step,
it was possible to set gain values as low as 5 (-29.5dB / 8%).
Actual HW seems to use similar ranges for input amplifiers.

Signed-off-by: Martin Wilck <martin.wilck@ts.fujitsu.com>
---
 hw/audio/hda-codec-common.h | 23 +++++++++++++++--------
 hw/audio/hda-codec.c        | 23 +++++++++++++++++------
 2 files changed, 32 insertions(+), 14 deletions(-)

diff --git a/hw/audio/hda-codec-common.h b/hw/audio/hda-codec-common.h
index b4fdb51..d59781b 100644
--- a/hw/audio/hda-codec-common.h
+++ b/hw/audio/hda-codec-common.h
@@ -28,16 +28,22 @@ 
 #define QEMU_HDA_ID_OUTPUT  ((QEMU_HDA_ID_VENDOR << 16) | 0x12)
 #define QEMU_HDA_ID_DUPLEX  ((QEMU_HDA_ID_VENDOR << 16) | 0x22)
 #define QEMU_HDA_ID_MICRO   ((QEMU_HDA_ID_VENDOR << 16) | 0x32)
-#define QEMU_HDA_AMP_CAPS                                               \
+#define QEMU_HDA_AMP_OUT_CAPS						\
     (AC_AMPCAP_MUTE |                                                   \
-     (QEMU_HDA_AMP_STEPS << AC_AMPCAP_OFFSET_SHIFT)    |                \
-     (QEMU_HDA_AMP_STEPS << AC_AMPCAP_NUM_STEPS_SHIFT) |                \
-     (3                  << AC_AMPCAP_STEP_SIZE_SHIFT))
+     (QEMU_HDA_AMP_OUT_STEPS << AC_AMPCAP_OFFSET_SHIFT)    |            \
+     (QEMU_HDA_AMP_OUT_STEPS << AC_AMPCAP_NUM_STEPS_SHIFT) |            \
+     (QEMU_HDA_AMP_OUT_STEP_SIZE << AC_AMPCAP_STEP_SIZE_SHIFT))
+#define QEMU_HDA_AMP_IN_CAPS						\
+    (AC_AMPCAP_MUTE |                                                   \
+     (QEMU_HDA_AMP_IN_STEPS << AC_AMPCAP_OFFSET_SHIFT)    |             \
+     (QEMU_HDA_AMP_IN_STEPS << AC_AMPCAP_NUM_STEPS_SHIFT) |             \
+     (QEMU_HDA_AMP_IN_STEP_SIZE << AC_AMPCAP_STEP_SIZE_SHIFT))
 #else
 #define QEMU_HDA_ID_OUTPUT  ((QEMU_HDA_ID_VENDOR << 16) | 0x11)
 #define QEMU_HDA_ID_DUPLEX  ((QEMU_HDA_ID_VENDOR << 16) | 0x21)
 #define QEMU_HDA_ID_MICRO   ((QEMU_HDA_ID_VENDOR << 16) | 0x31)
-#define QEMU_HDA_AMP_CAPS   QEMU_HDA_AMP_NONE
+#define QEMU_HDA_AMP_OUT_CAPS   QEMU_HDA_AMP_NONE
+#define QEMU_HDA_AMP_IN_CAPS   QEMU_HDA_AMP_NONE
 #endif
 
 
@@ -61,7 +67,7 @@  static const desc_param glue(common_params_audio_dac_, PARAM)[] = {
         .val = QEMU_HDA_AMP_NONE,
     },{
         .id  = AC_PAR_AMP_OUT_CAP,
-        .val = QEMU_HDA_AMP_CAPS,
+        .val = QEMU_HDA_AMP_OUT_CAPS,
     },
 };
 
@@ -86,7 +92,7 @@  static const desc_param glue(common_params_audio_adc_, PARAM)[] = {
         .val = AC_SUPFMT_PCM,
     },{
         .id  = AC_PAR_AMP_IN_CAP,
-        .val = QEMU_HDA_AMP_CAPS,
+        .val = QEMU_HDA_AMP_IN_CAPS,
     },{
         .id  = AC_PAR_AMP_OUT_CAP,
         .val = QEMU_HDA_AMP_NONE,
@@ -453,4 +459,5 @@  static const desc_codec glue(micro_, PARAM) = {
 #undef QEMU_HDA_ID_OUTPUT
 #undef QEMU_HDA_ID_DUPLEX
 #undef QEMU_HDA_ID_MICRO
-#undef QEMU_HDA_AMP_CAPS
+#undef QEMU_HDA_AMP_IN_CAPS
+#undef QEMU_HDA_AMP_OUT_CAPS
diff --git a/hw/audio/hda-codec.c b/hw/audio/hda-codec.c
index 3c03ff5..44c9a28 100644
--- a/hw/audio/hda-codec.c
+++ b/hw/audio/hda-codec.c
@@ -116,7 +116,17 @@  static void hda_codec_parse_fmt(uint32_t format, struct audsettings *as)
 #define QEMU_HDA_PCM_FORMATS (AC_SUPPCM_BITS_16 |       \
                               0x1fc /* 16 -> 96 kHz */)
 #define QEMU_HDA_AMP_NONE    (0)
-#define QEMU_HDA_AMP_STEPS   0x4a
+/* Amplifier properties */
+/* Step size: 0: 0.25dB 1: 0.5dB 2: 0.75dB 3: 1dB */
+/* 
+   Until we have a way to propagate dB values cleanly to the host
+   e.g. through spice, it is better to use a smaller dynamic range
+   for input. Here we use 0x40 * 0.5 dB = 32dB.
+*/
+#define QEMU_HDA_AMP_OUT_STEPS   0x4a
+#define QEMU_HDA_AMP_OUT_STEP_SIZE  3
+#define QEMU_HDA_AMP_IN_STEPS    0x4a
+#define QEMU_HDA_AMP_IN_STEP_SIZE   1
 
 #define   PARAM mixemu
 #define   HDA_MIXER
@@ -258,15 +268,16 @@  static void hda_audio_set_amp(HDAAudioStream *st)
     left  = st->mute_left  ? 0 : st->gain_left;
     right = st->mute_right ? 0 : st->gain_right;
 
-    left = left * 255 / QEMU_HDA_AMP_STEPS;
-    right = right * 255 / QEMU_HDA_AMP_STEPS;
-
     if (!st->state->mixer) {
         return;
     }
     if (st->output) {
+        left = left * 255 / QEMU_HDA_AMP_OUT_STEPS;
+        right = right * 255 / QEMU_HDA_AMP_OUT_STEPS;
         AUD_set_volume_out(st->voice.out, muted, left, right);
     } else {
+        left = left * 255 / QEMU_HDA_AMP_IN_STEPS;
+        right = right * 255 / QEMU_HDA_AMP_IN_STEPS;
         AUD_set_volume_in(st->voice.in, muted, left, right);
     }
 }
@@ -502,8 +513,8 @@  static int hda_audio_init(HDACodecDevice *hda, const struct desc_codec *desc)
             st->node = node;
             if (type == AC_WID_AUD_OUT) {
                 /* unmute output by default */
-                st->gain_left = QEMU_HDA_AMP_STEPS;
-                st->gain_right = QEMU_HDA_AMP_STEPS;
+                st->gain_left = QEMU_HDA_AMP_OUT_STEPS;
+                st->gain_right = QEMU_HDA_AMP_OUT_STEPS;
                 st->bpos = sizeof(st->buf);
                 st->output = true;
             } else {
-- 
2.1.0