commit ecbf2ee4797255fc1290b237bd9492e91269f1a8
author Dean Wheatley <dwhea@dolby.com> Fri Mar 04 10:51:36 2022 +1100
committer Oscar Azucena <oscarazu@google.com> Fri Jul 08 05:16:41 2022 +0000
tree 1179d4d3a93ea8f90e378760ec44f33054319c25
parent d082f477c2089e68c061badb3e6ce55ec950ba96

Preference multichannel pcm direct output over stereo mixer

If a direct output is available for a multichannel output request,
and the mixer outputs a channel count lower than the track, try the
direct output first, and fall-back to the non-direct output if
not successful.

Bug: 238286324
Test: atest audiopolicy_tests:AudioPolicyManagerCarTest#GetOutputForAttrAtmosOutputAfterRegisteringPolicyMix
Change-Id: Ic7265bd09556ab7dd0660df5b307d151abace503

services/audiopolicy/managerdefault/AudioPolicyManager.cpp

diff --git a/services/audiopolicy/managerdefault/AudioPolicyManager.cpp b/services/audiopolicy/managerdefault/AudioPolicyManager.cpp
index 6536e90..912d53a 100644
--- a/services/audiopolicy/managerdefault/AudioPolicyManager.cpp
+++ b/services/audiopolicy/managerdefault/AudioPolicyManager.cpp
@@ -1186,19 +1186,27 @@
                                                   primaryMix->mDeviceAddress,
                                                   AUDIO_FORMAT_DEFAULT);
         sp<SwAudioOutputDescriptor> policyDesc = primaryMix->getOutput();
-        if (deviceDesc != nullptr
-                && (policyDesc == nullptr || (policyDesc->mFlags & AUDIO_OUTPUT_FLAG_DIRECT))) {
+        bool tryDirectForFlags = policyDesc == nullptr ||
+                (policyDesc->mFlags & AUDIO_OUTPUT_FLAG_DIRECT);
+        // if a direct output can be opened to deliver the track's multi-channel content to the
+        // output rather than being downmixed by the primary output, then use this direct
+        // output by by-passing the primary mix if possible, otherwise fall-through to primary
+        // mix.
+        bool tryDirectForChannelMask = policyDesc != nullptr
+                    && (audio_channel_count_from_out_mask(policyDesc->getConfig().channel_mask) <
+                        audio_channel_count_from_out_mask(config->channel_mask));
+        if (deviceDesc != nullptr && (tryDirectForFlags || tryDirectForChannelMask)) {
             audio_io_handle_t newOutput;
             status = openDirectOutput(
                     *stream, session, config,
                     (audio_output_flags_t)(*flags | AUDIO_OUTPUT_FLAG_DIRECT),
                     DeviceVector(deviceDesc), &newOutput);
-            if (status != NO_ERROR) {
-                policyDesc = nullptr;
-            } else {
+            if (status == NO_ERROR) {
                 policyDesc = mOutputs.valueFor(newOutput);
                 primaryMix->setOutput(policyDesc);
-            }
+            } else if (tryDirectForFlags) {
+                policyDesc = nullptr;
+            } // otherwise use primary if available.
         }
         if (policyDesc != nullptr) {
             policyDesc->mPolicyMix = primaryMix;