Various playback issues on Pixel 7a with setPreferredMixerAttributes (Android Canary 202512)

Android version(s): Android Canary 202512
Android device(s): Pixel 7a
Oboe version:
App name used for testing: OboeTester at latest commit (650dfefb43011355857ad4894a1bd45b593c27c8) with small patch:

```diff
diff --git a/apps/OboeTester/app/src/main/java/com/mobileer/oboetester/TestAudioActivity.java b/apps/OboeTester/app/src/main/java/com/mobileer/oboetester/TestAudioActivity.java
index 83abd871..2799faa5 100644
--- a/apps/OboeTester/app/src/main/java/com/mobileer/oboetester/TestAudioActivity.java
+++ b/apps/OboeTester/app/src/main/java/com/mobileer/oboetester/TestAudioActivity.java
@@ -35,6 +35,7 @@ import android.media.AudioAttributes;
import android.media.AudioDeviceInfo;
import android.media.AudioFocusRequest;
import android.media.AudioManager;
+import android.media.AudioMixerAttributes;
import android.os.Build;
import android.os.Bundle;
import android.os.Handler;
@@ -59,6 +60,8 @@ import java.io.InputStream;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
import java.util.Locale;

/**
@@ -744,6 +747,39 @@ abstract class TestAudioActivity extends AppCompatActivity implements AudioManag
// Always close existing streams before opening new ones.
closeAudioLocked();

+ if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.UPSIDE_DOWN_CAKE) {
+ AudioManager audioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
+ List info = Arrays.asList(audioManager.getDevices(AudioManager.GET_DEVICES_OUTPUTS));
+ for (AudioDeviceInfo device : info) {
+ List attr = audioManager.getSupportedMixerAttributes(device);
+ if (attr.isEmpty()) continue;
+ attr.sort((a, b) -> {
+ if (a.getMixerBehavior() != b.getMixerBehavior()) {
+ return a.getMixerBehavior() == AudioMixerAttributes.MIXER_BEHAVIOR_BIT_PERFECT ? 1 : -1;
+ }
+ if (a.getFormat().getSampleRate() != b.getFormat().getSampleRate()) {
+ return Math.abs(a.getFormat().getSampleRate()-88200) > Math.abs(b.getFormat().getSampleRate()-88200) ? 1 : -1;
+ }
+ if (a.getFormat().getChannelCount() != b.getFormat().getChannelCount()) {
+ return a.getFormat().getChannelCount() > b.getFormat().getChannelCount() ? 1 : -1;
+ }
+ if (a.getFormat().getEncoding() != b.getFormat().getEncoding()) { // :)
+ return a.getFormat().getEncoding() > b.getFormat().getEncoding() ? 1 : -1;
+ }
+ return 0;
+ });
+ audioManager.setPreferredMixerAttributes(new AudioAttributes.Builder()
+ .setUsage(AudioAttributes.USAGE_MEDIA)
+ .setContentType(AudioAttributes.CONTENT_TYPE_MUSIC)
+ .build(), device, attr.get(0));
+ }
+ try {
+ Thread.sleep(500);
+ } catch (InterruptedException e) {
+ throw new RuntimeException(e);
+ }
+ }
+
updateNativeAudioParameters();

if (!isTestConfiguredUsingBundle()) {
@@ -1061,6 +1097,19 @@ abstract class TestAudioActivity extends AppCompatActivity implements AudioManag
onStopAllContexts();
}
}
+
+ if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.UPSIDE_DOWN_CAKE) {
+ AudioManager audioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
+ List info = Arrays.asList(audioManager.getDevices(AudioManager.GET_DEVICES_OUTPUTS));
+ for (AudioDeviceInfo device : info) {
+ List attr = audioManager.getSupportedMixerAttributes(device);
+ if (attr.isEmpty()) continue;
+ audioManager.clearPreferredMixerAttributes(new AudioAttributes.Builder()
+ .setUsage(AudioAttributes.USAGE_MEDIA)
+ .setContentType(AudioAttributes.CONTENT_TYPE_MUSIC)
+ .build(), device);
+ }
+ }
}

public void runTest() {
```

**Short description**
When using the setPreferredMixerAttributes API, playback does not work. Either OboeTester says the stream was closed or OboeTester thinks the stream is playing but aocd log-spams with invalid state error:

**Steps to reproduce**

1.Plug in USB dac that supports 88.2k and 192k sample rate among others (did not test with others)
2.install & open patched OboeTester
3.Test Output
4.Open, Start

**Expected behavior**

Normal OboeTester tone

**Actual behavior**

No sound and error spam in logcat:

```
2026-01-31 20:53:13.181 916-14410 audio_hw_waves android.hardware.audio.service D waves_usecase_event: hifi-playback stop
2026-01-31 20:53:13.181 1168-1168 AOC aocd D F1:MSG: controller.cc, 275: AudioOutCtrl: cmd ID: 0x010f, tag: 0xb9 [cntr = 14922]
2026-01-31 20:53:13.182 1168-1168 AOC aocd D F1:Unregistered Source 13 [USBHiFi] from Sink 3 [USB]
2026-01-31 20:53:13.182 1168-1168 AOC aocd D F1:AT Map:0 (LL:0), 0 EPs active, Power: Yes, Config: No
2026-01-31 20:53:13.182 1168-1168 AOC aocd D F1:Mixer 3 configuration changed: (0)
2026-01-31 20:53:13.182 1168-1168 AOC aocd D F1:Sink 3 Configuration changed: ULL (disabled)
2026-01-31 20:53:13.182 1168-1168 AOC aocd D F1:MSG: usb.cc, 567: Stop playback, TX enabled = 0, RX enabled = 0
2026-01-31 20:53:13.182 1168-1168 AOC aocd D F1:MSG: controller.cc, 910: AudioOutCtrl: ipc: audio_output_co, cmd ID: 0x010f, tag: 0xb9, rc: 0
2026-01-31 20:53:13.183 1168-1168 AOC aocd D H0:Mixer AMixUSB: 480 samples (0000/0000) (OFF)
2026-01-31 20:53:13.199 916-916 writer android.hardware.audio.service W type=1400 audit(0.0:3872): avc: denied { read } for name="u:object_r:default_prop:s0" dev="tmpfs" ino=182 scontext=u:r:hal_audio_default:s0 tcontext=u:object_r:default_prop:s0 tclass=file permissive=0
2026-01-31 20:53:13.202 916-14410 audio_hw android.hardware.audio.service D prepare hifi-playback
2026-01-31 20:53:13.203 916-14410 audio_hw android.hardware.audio.service D hifi-playback:
2026-01-31 20:53:13.203 916-14410 audio_hw android.hardware.audio.service D rx:
2026-01-31 20:53:13.203 916-14410 audio_hw android.hardware.audio.service D #0: OUT_USB_HEADPHONE_BE_CFG 2
2026-01-31 20:53:13.203 916-14410 audio_hw_usb android.hardware.audio.service E select_capability: fail to convert to index for fmt 0x0 endian 0
2026-01-31 20:53:13.203 916-14410 audio_hw_usb android.hardware.audio.service D refine_setting: card 1 dev 0x4000000
2026-01-31 20:53:13.203 916-14410 audio_hw android.hardware.audio.service D select bit 32 rate 88200 ch 2 for intf USB_RX
2026-01-31 20:53:13.203 916-14410 audio_hw_usb android.hardware.audio.service D update_device_active_state: active_device_mask 0x1
2026-01-31 20:53:13.203 916-14410 audio_hw_usb android.hardware.audio.service D apply_setting: card 1 dev 0x4000000
2026-01-31 20:53:13.203 916-14410 audio_hw_usb android.hardware.audio.service D apply_setting: ep: 1 bit 32 ch 2 rate 88200
2026-01-31 20:53:13.203 916-14410 audio_hw_usb android.hardware.audio.service D usb_device_config: rx proxy open (is_active 0)
2026-01-31 20:53:13.203 916-14410 audio_hw_usb android.hardware.audio.service D usb_device_config: bit 32, format 0x3, rate 88200 chan 2
2026-01-31 20:53:13.203 916-14410 audio_hw_usb android.hardware.audio.service W Invalid sample rate 88200 - using default 48000.
2026-01-31 20:53:13.204 1168-1168 AOC aocd D F1:MSG: controller.cc, 275: AudioOutCtrl: cmd ID: 0x0112, tag: 0xba [cntr = 14923]
2026-01-31 20:53:13.204 916-14410 libc android.hardware.audio.service W Access denied finding property "ro.audio.usb.period_us"
2026-01-31 20:53:13.204 1168-1168 AOC aocd E F1:ERR: audio_hardware_sink_usb.cc, 453: USB TX: Unsupported sample rate requested (88200)!
2026-01-31 20:53:13.204 1168-1168 AOC aocd E F1:ERR: controller.cc, 906: AudioOutCtrl: ipc: audio_output_co, cmd ID: 0x0112, tag: 0xba, rc: -1
2026-01-31 20:53:13.205 916-14410 audio_hw_usb android.hardware.audio.service W usb_device_config: usb_alsa_repare failed ret -22
2026-01-31 20:53:13.205 916-14410 audio_hw_usb android.hardware.audio.service E apply_setting: usb_device_config failed -22
2026-01-31 20:53:13.205 916-14410 audio_hw_soundtrigger android.hardware.audio.service D st_comm_aud_event_monitor:codec dev:17 active
2026-01-31 20:53:13.205 916-14410 audio_hw_aoc android.hardware.audio.service I Mode Ambient is already selected
2026-01-31 20:53:13.205 916-14410 audio_route android.hardware.audio.service D Apply path: hifi-playbackP usb-headphone
2026-01-31 20:53:13.206 1168-1168 AOC aocd D F1:MSG: controller.cc, 275: AudioOutCtrl: cmd ID: 0x010f, tag: 0xbb [cntr = 14924]
2026-01-31 20:53:13.206 916-14410 audio_hw_aoc_route android.hardware.audio.service D hifi-playbackP usb-headphone 1
2026-01-31 20:53:13.206 1168-1168 AOC aocd D F1:Source 13 [USBHiFi] mastered by sink 3 [USB]
2026-01-31 20:53:13.206 1168-1168 AOC aocd D F1:AT Map:2000 (LL:0), 1 EPs active, Power: Yes, Config: No
2026-01-31 20:53:13.207 1168-1168 AOC aocd D F1:Mixer 3 configuration changed: (2000)
2026-01-31 20:53:13.207 1168-1168 AOC aocd D F1:Sink 3 Configuration changed: ULL (enabled)
2026-01-31 20:53:13.207 1168-1168 AOC aocd D F1:AHWSinkUSB started: 48 samples (32-bit,2 ch,48 kHz) block 384 ts_en 0
2026-01-31 20:53:13.207 916-14410 audio_hw_waves android.hardware.audio.service D waves_usecase_event: hifi-playback start
2026-01-31 20:53:13.207 916-14410 audio_hw_waves android.hardware.audio.service D waves_usecase_event: trigger to update tuning when first track is running.
2026-01-31 20:53:13.208 1168-1168 AOC aocd E F1:ERR: audio_hardware_sink_usb.cc, 2116: Attempt to start playback without configuration
```

Notably: `USB TX: Unsupported sample rate requested (88200)!` - then 1. why is it exposed in API that lists supported sample rates? 2. Why not just support it, it's just software limitation anyway..

**Device**

Pixel 7a

**Any additional context**

This is a regression from Android 14 QPR3 where playback was working but using wrong sample rate (which was what I was trying to find out if it's fixed now). Well that's to say it never worked properly on this device as far as I know.

Also, if you replace 88200 with 192000 in the patch above, then playback will work but it sounds like its constantly underrunning and the tone also seems too high. So I assume nobody had validated this API on Pixel 7a.