"flat audio" when using AAudio low-latency option

[icculus]

Okay, let's go ahead and add this patch for SDL 2.30 and I'll figure out what device was getting flat audio and see if I can improve that hint logic.

Originally posted by @slouken in https://github.com/libsdl-org/SDL/issues/8888#issuecomment-1904938459

Just adding this issue so we remember to look at this later.

[slouken]

Here's the log from the affected system:

10-10 17:52:30.682 19827 19827 V SDL     : nativeSetupJNI()
10-10 17:52:30.684 19827 19827 V SDL     : AUDIO nativeSetupJNI()
10-10 17:52:30.684 19827 19827 V SDL     : CONTROLLER nativeSetupJNI()
10-10 17:52:31.168 19827 19913 I SDL/APP : AAUDIO_Init
10-10 17:52:31.169 19827 19913 I SDL/APP : SDL AAUDIO_Init OK
10-10 17:52:31.169 19827 19913 I SDL/APP : AAUDIO_OpenDevice
10-10 17:52:31.170 19827 19913 I SDL/APP : AAudio Try to open 48000 hz 16 bit chan 2 LE samples 1024
10-10 17:52:31.170 19827 19913 I AAudio  : AAudioStreamBuilder_openStream() called ----------------------------------------
10-10 17:52:31.170 19827 19913 I AudioStreamBuilder: rate   =      0, channels  = 0, channelMask = 0, format   = 0, sharing = SH, dir = OUTPUT
10-10 17:52:31.170 19827 19913 I AudioStreamBuilder: device =      0, sessionId = -1, perfMode = 10, callback: ON with frames = 0
10-10 17:52:31.170 19827 19913 I AudioStreamBuilder: usage  =      0, contentType = 0, inputPreset = 0, allowedCapturePolicy = 0
10-10 17:52:31.170 19827 19913 I AudioStreamBuilder: privacy sensitive = false, opPackageName = (null), attributionTag = (null)
10-10 17:52:31.177 19827 19913 D AudioStreamBuilder: build() MMAP not used because AAUDIO_PERFORMANCE_MODE_LOW_LATENCY not requested.
10-10 17:52:31.178 19827 19913 D AudioStreamTrack: open(), request notificationFrames = 0, frameCount = 0
10-10 17:52:31.187  5096 18689 V APM_AudioPolicyManager: getOutputForAttrInt() attributes={ Content type: AUDIO_CONTENT_TYPE_MUSIC Usage: AUDIO_USAGE_MEDIA Source: AUDIO_SOURCE_DEFAULT Flags: 0x0 Tags:  } stream=AUDIO_STREAM_MUSIC session 100337 selectedDeviceId 0
10-10 17:52:31.188  5096 18689 I APM_AudioPolicyManager: selectOutputFlags: remove ULL flag for dolby
10-10 17:52:31.188  5096 18689 V APM_AudioPolicyManager: getOutputForAttrInt() device {AUDIO_DEVICE_OUT_SPEAKER, @:}, sampling rate 0, format 0x5, channel mask 0x3, flags 0x8 stream AUDIO_STREAM_MUSIC
10-10 17:52:31.188  5096 18689 V APM_AudioPolicyManager: selectOutput new bestOutput 13 criteria 0 100 0 0 0 1 2 2
10-10 17:52:31.188  5096 18689 V APM_AudioPolicyManager: getOutputForAttrInt returns output 13 selectedDeviceId 2
10-10 17:52:31.188  5096 18689 V APM_AudioPolicyManager: getOutputForAttr() returns output 13 requestedPortId 0 selectedDeviceId 2 for port ID 14120
10-10 17:52:31.189  5096 18689 I AudioFlinger: Find game Uid 10764, change usage
10-10 17:52:31.189  5096 18689 I AudioFlinger: nonSecFlag 0, secFlag 0, outputFlags a
10-10 17:52:31.189  5096 18689 D AudioFlinger: Client defaulted notificationFrames to 1282 for frameCount 3848
10-10 17:52:31.192  5096 18689 D AF::TrackHandle: OpPlayAudio: track:10711 usage:14 not muted
10-10 17:52:31.197 19827 19913 D AudioTrack: setVolume(1.000000, 1.000000) pid : 19827
10-10 17:52:31.197 19827 19913 D AAudioStream: setState(s#1) from 0 to 2
10-10 17:52:31.200 19827 19913 I AAudio  : AAudioStreamBuilder_openStream() returns 0 = AAUDIO_OK for s#1 ----------------
10-10 17:52:31.200 19827 19913 I SDL/APP : AAudio got AAUDIO_FORMAT_PCM_FLOAT
10-10 17:52:31.200 19827 19913 I SDL/APP : AAudio Actually opened 48000 hz 32 bit chan 2 LE samples 1924, buffers 2
10-10 17:52:31.200 19827 19913 D AAudio  : AAudioStream_requestStart(s#1) called --------------
10-10 17:52:31.200 19827 19913 D AAudioStream: setState(s#1) from 2 to 3
10-10 17:52:31.201  5096 18689 I AudioPolicyEffectException: MySpaceHandler::checkDetachCondition media 1, ring 0, mp 0
10-10 17:52:31.201  5096 18689 I AudioPolicyEffectException: MySpace detach value 1
10-10 17:52:31.201  5096 18689 V APM_AudioPolicyManager: startOutput portId 14120
10-10 17:52:31.202  5096 18689 V APM_AudioPolicyManager: startOutput() output 13, stream 3, session 100337
10-10 17:52:31.202  5096 18689 V APM_AudioPolicyManager: setBeaconMute(1) mBeaconMuteRefCount=9 mBeaconPlayingRefCount=0
10-10 17:52:31.202  5096 18689 V APM_AudioPolicyManager: selectOutputForMusicEffects activeOnly 1 output 13 flags 0x0000000a
10-10 17:52:31.202  5096 18689 V APM_AudioPolicyManager: selectOutputForMusicEffects selected output 13
10-10 17:52:31.203  5096 18689 V APM_AudioPolicyManager: getNewOutputDevices selected devices {AUDIO_DEVICE_OUT_SPEAKER, @:}
10-10 17:52:31.203  5096 18689 V APM_AudioPolicyManager: setOutputDevices device {AUDIO_DEVICE_OUT_SPEAKER, @:} delayMs 0
10-10 17:52:31.203  5096 18689 V APM_AudioPolicyManager: setOutputDevices() prevDevice {AUDIO_DEVICE_OUT_SPEAKER, @:}
10-10 17:52:31.203  5096 18689 V APM_AudioPolicyManager: setOutputDevices: suppressing checkDeviceMuteStrategies
10-10 17:52:31.203  5096 18689 V APM_AudioPolicyManager: setOutputDevices setting same device {AUDIO_DEVICE_OUT_SPEAKER, @:} or null device, force=0, patch handle=14080
10-10 17:52:31.203  5096 18689 V APM_AudioPolicyManager: computeVolume: stream 3, index 12, volume 0.316228, deviceTypes 0x2
10-10 17:52:31.204  5096 18689 V APM_AudioPolicyManager: computeVolume: stream 3, index 13, volume 0.446684, deviceTypes 0x2
10-10 17:52:31.207  5096 18689 I AudioFlinger: updateStageIndex new -1309
10-10 17:52:31.208 19827 19913 D AAudio  : AAudioStream_requestStart(s#1) returned 0 ---------
10-10 17:52:31.208 19827 19855 D AudioStreamLegacy: onAudioDeviceUpdate(deviceId = 2)
10-10 17:52:31.208 19827 19913 I SDL/APP : SDL AAudioStream_requestStart OK
10-10 17:52:31.209  5096  5330 I AudioSAEffectSecPlus: command EFFECT_CMD_SET_VOLUME left = 0.316228, right =0.316228
10-10 17:52:31.210  5008  4428 D audio_hw_primary: primary_out-out_update_source_metadata: called, but not implemented yet
10-10 17:52:31.210  5008  4428 D audio_hw_primary: primary_out-out_update_source_metadata: This stream has 1 tracks
10-10 17:52:31.210  5008  4428 D audio_hw_primary: 1 Track has Usage(14), Content Type(2), Gain(0.000000)
10-10 17:52:31.211  5354  5354 D AudioPlayerStateMonitor: Found a new active media playback. AudioPlaybackConfiguration piid:77687 deviceId:2 type:AAudio u/pid:10764/19827 state:started attr:AudioAttributes: usage=USAGE_MEDIA content=CONTENT_TYPE_UNKNOWN flags=0x0 tags= bundle=null sessionId:-1

I'm not sure how to detect this case though?

[eres-j]

Hi, I ran into this issue with SDL2 release-2.30.0 which don't seems to have the hint patch. My device is a Samsung Galaxy S29+ which I believe could handle low latency audio. I read AAudio documentation and I think we might use it incorrectly:

In the current version of AAudio, in order to achieve the lowest possible latency you must use the AAUDIO_PERFORMANCE_MODE_LOW_LATENCY performance mode along with a high-priority callback.

In SDL2 we use AAudioStream_write which is fine for AAUDIO_PERFORMANCE_MODE_NONE but maybe not for AAUDIO_PERFORMANCE_MODE_LOW_LATENCY. In this case I'm pretty sure we should use an high priority callback using AAudioStreamBuilder_setDataCallback.

I would be happy to contribute and fix it myself but my knowledge of SDL2 backend is very limited.

[slouken]

SDL3 uses a high performance callback and has the same issue.

[icculus]

If you have a device that can reproduce this and you can record the sound in some way, I'd like to understand what "flat audio" sounds like exactly.

[eres-j]

The volume is normalized, be warned that it could sound very loudly! Android_good_vs_bad_audio_sine440.zip I recorded it using a microphone, first part is how it should sound (sine wave at 440Hz) and the second is how it actually sound. I tried to increase and decrease chunk size in Mix_OpenAudio call but it didn't changed much.

[brainos233]

This problem exists on Huawei Matepad 11, after revert https://github.com/libsdl-org/SDL/commit/8367b00e8c816a7878060ef9479e2e1482ec9693 and manually remove AAUDIO_PERFORMANCE_MODE_LOW_LATENCY , this "flat audio" is reported has fixed.

diff --git a/src/audio/aaudio/SDL_aaudio.c b/src/audio/aaudio/SDL_aaudio.c
index 401fef6a8..3c599db8a 100644
--- a/src/audio/aaudio/SDL_aaudio.c
+++ b/src/audio/aaudio/SDL_aaudio.c
@@ -239,7 +239,6 @@ static int RebuildAAudioStream(SDL_AudioDevice *device)
     }
 
     ctx.AAudioStreamBuilder_setErrorCallback(ctx.builder, aaudio_errorCallback, hidden);
-    ctx.AAudioStreamBuilder_setPerformanceMode(ctx.builder, AAUDIO_PERFORMANCE_MODE_LOW_LATENCY);
 
     LOGI("AAudio Try to reopen %u hz %u bit chan %u %s samples %u",
          device->spec.freq, SDL_AUDIO_BITSIZE(device->spec.format),