ao_wasapi: add `--wasapi-exclusive-buffer` option

This allows users to set buffer duration in exclusive mode. We have
been using the default device period as the buffer size and it is
robust enough in most cases. However, on some devices there are
horrible glitches after a stream reset. Unfortunately, the issue is not
consistently reproducible, but using a smaller buffer size (e.g., the
minimum device period) seems to resolve the problem.

Fixes #13715.

3 files changed, 27 insertions, 9 deletions

diff --git a/audio/out/ao_wasapi.c b/audio/out/ao_wasapi.c
index d986d80226..58d2acd09a 100644
--- a/audio/out/ao_wasapi.c
+++ b/audio/out/ao_wasapi.c
@@ -526,4 +526,10 @@ const struct ao_driver audio_out_wasapi = {
     .hotplug_init   = hotplug_init,
     .hotplug_uninit = hotplug_uninit,
     .priv_size      = sizeof(wasapi_state),
+    .options_prefix = "wasapi",
+    .options        = (const struct m_option[]) {
+        {"exclusive-buffer", OPT_CHOICE(opt_exclusive_buffer,
+            {"default", 0}, {"min", -1}), M_RANGE(1, 2000000)},
+        {0}
+    },
 };
diff --git a/audio/out/ao_wasapi.h b/audio/out/ao_wasapi.h
index 4e5e9c8a67..e294e317c3 100644
--- a/audio/out/ao_wasapi.h
+++ b/audio/out/ao_wasapi.h
@@ -91,6 +91,7 @@ typedef struct wasapi_state {
 
     // ao options
     int opt_exclusive;
+    int opt_exclusive_buffer; // exclusive mode buffer duration in us
 
     // format info
     WAVEFORMATEXTENSIBLE format;
diff --git a/audio/out/ao_wasapi_utils.c b/audio/out/ao_wasapi_utils.c
index 7e85f75eab..8ff6523303 100644
--- a/audio/out/ao_wasapi_utils.c
+++ b/audio/out/ao_wasapi_utils.c
@@ -640,16 +640,25 @@ static HRESULT fix_format(struct ao *ao, bool align_hack)
     struct wasapi_state *state = ao->priv;
 
     MP_DBG(state, "IAudioClient::GetDevicePeriod\n");
-    REFERENCE_TIME devicePeriod;
-    HRESULT hr = IAudioClient_GetDevicePeriod(state->pAudioClient,&devicePeriod,
-                                              NULL);
-    MP_VERBOSE(state, "Device period: %.2g ms\n",
-               (double) devicePeriod / 10000.0 );
+    REFERENCE_TIME defaultPeriod, minPeriod;
+    HRESULT hr = IAudioClient_GetDevicePeriod(state->pAudioClient,&defaultPeriod,
+                                              &minPeriod);
+    MP_VERBOSE(state, "Device period: default %lld us, minimum %lld us\n",
+               defaultPeriod / 10, minPeriod / 10);
 
-    REFERENCE_TIME bufferDuration = devicePeriod;
+    REFERENCE_TIME bufferDuration;
     if (state->share_mode == AUDCLNT_SHAREMODE_SHARED) {
         // for shared mode, use integer multiple of device period close to 50ms
-        bufferDuration = devicePeriod * ceil(50.0 * 10000.0 / devicePeriod);
+        bufferDuration = defaultPeriod * ceil(50.0 * 10000.0 / defaultPeriod);
+    } else if (state->opt_exclusive_buffer == 0) {
+        bufferDuration = defaultPeriod;
+    } else {
+        if (state->opt_exclusive_buffer > 0 && !align_hack) {
+            MP_VERBOSE(state, "Requested buffer duration: %d us\n",
+                       state->opt_exclusive_buffer);
+        }
+        bufferDuration = MPMAX((REFERENCE_TIME) state->opt_exclusive_buffer * 10,
+                               minPeriod);
     }
 
     // handle unsupported buffer size if AUDCLNT_E_BUFFER_SIZE_NOT_ALIGNED was
@@ -662,6 +671,8 @@ static HRESULT fix_format(struct ao *ao, bool align_hack)
              * state->bufferFrameCount));
     }
 
+    MP_VERBOSE(state, "Trying buffer duration %lld us\n", bufferDuration / 10);
+
     REFERENCE_TIME bufferPeriod =
         state->share_mode == AUDCLNT_SHAREMODE_EXCLUSIVE ? bufferDuration : 0;
 
@@ -694,8 +705,8 @@ static HRESULT fix_format(struct ao *ao, bool align_hack)
     bufferDuration = (REFERENCE_TIME) (0.5 +
         (10000.0 * 1000 / state->format.Format.nSamplesPerSec
          * state->bufferFrameCount));
-    MP_VERBOSE(state, "Buffer frame count: %"PRIu32" (%.2g ms)\n",
-               state->bufferFrameCount, (double) bufferDuration / 10000.0 );
+    MP_VERBOSE(state, "Buffer frame count: %"PRIu32" (%lld us)\n",
+               state->bufferFrameCount, bufferDuration / 10);
 
     hr = init_clock(state);
     EXIT_ON_ERROR(hr);