[obs] audio: capture guest playback

Subscribe the OBS source as a playback-only LGMP audio client. Decode
the advertised formats and channel maps, then resample into the OBS
clock domain without participating in driver clock feedback.

Keep queue and resampler storage fixed in the packet path.

obs/lg.c

@@ -42,6 +42,7 @@
 #include "hdrpq.effect.h"
 #include "cursor.effect.h"
 #include "frame_scheduler.h"
+#include "audio.h"
 
 #define LG_FRAME_TIMING_SPIN_COUNT 4096
 
@@ -136,6 +137,7 @@ typedef struct
   pthread_mutex_t      pointerLock;
   LGFrameScheduler     frameScheduler;
   _Atomic(bool)        sourceActive;
+  LGOBSAudio         * audio;
 
   bool                 cursorMono;
   gs_texture_t       * cursorTex;
@@ -439,6 +441,20 @@ static void * lgCreate(obs_data_t * settings, obs_source_t * context)
   atomic_store(&this->cursorTransformVer, 0);
   atomic_store(&this->sdrWhiteLevel, KVMFR_SDR_WHITE_LEVEL_DEFAULT);
   atomic_store(&this->sourceActive, obs_source_active(context));
+  if (!lgObsAudioCreate(&this->audio, context))
+  {
+    blog(LOG_ERROR, "Failed to initialize Looking Glass audio");
+    os_sem_destroy(this->frameSem);
+    os_sem_destroy(this->cursorSem);
+    pthread_mutex_destroy(&this->pointerLock);
+    obs_enter_graphics();
+    gs_effect_destroy(this->unpackEffect);
+    gs_effect_destroy(this->hdrEffect);
+    gs_effect_destroy(this->cursorEffect);
+    obs_leave_graphics();
+    bfree(this);
+    return NULL;
+  }
   lgUpdate(this, settings);
   return this;
 }
@@ -514,6 +530,7 @@ static void dmabufReset(LGPlugin * this)
 
 static void deinit(LGPlugin * this)
 {
+  lgObsAudioDisconnect(this->audio);
   bool closeShm = false;
   switch(this->state)
   {
@@ -610,6 +627,7 @@ static void lgDestroy(void * data)
 {
   LGPlugin * this = (LGPlugin *)data;
   deinit(this);
+  lgObsAudioDestroy(&this->audio);
   os_sem_destroy(this->frameSem );
   os_sem_destroy(this->cursorSem);
   pthread_mutex_destroy(&this->pointerLock);
@@ -626,6 +644,7 @@ static void lgDestroy(void * data)
 static void lgGetDefaults(obs_data_t * defaults)
 {
   obs_data_set_default_string(defaults, "shmFile", "/dev/kvmfr0");
+  obs_data_set_default_bool(defaults, "captureAudio", true);
 #if LIBOBS_API_MAJOR_VER >= 27
   obs_data_set_default_bool(defaults, "dmabuf", true);
 #endif
@@ -639,6 +658,8 @@ static obs_properties_t * lgGetProperties(void * data)
       obs_module_text("SHM File"), OBS_TEXT_DEFAULT);
   obs_properties_add_bool(props, "hideMouse",
       obs_module_text("Hide mouse cursor"));
+  obs_properties_add_bool(props, "captureAudio",
+      obs_module_text("Capture guest audio"));
 #if LIBOBS_API_MAJOR_VER >= 27
   obs_properties_add_bool(props, "dmabuf",
       obs_module_text("Use DMABUF import (requires kvmfr device)"));
@@ -771,6 +792,7 @@ static void * pointerThread(void * data)
     LGMPMessage msg;
 
     pthread_mutex_lock(&this->pointerLock);
+    lgObsAudioPumpPointer(this->audio, this->pointerQueue);
     if ((status = lgmpClientProcess(this->pointerQueue, &msg)) != LGMP_OK)
     {
       pthread_mutex_unlock(&this->pointerLock);
@@ -784,6 +806,31 @@ static void * pointerThread(void * data)
       continue;
     }
 
+    const uint32_t pointerTag = (uint32_t)(msg.udata >> 32);
+    if (pointerTag)
+    {
+      KVMFRAudioStreamResponse response;
+      const bool audioResponse =
+        pointerTag == KVMFR_AUDIO_CONTROL_TAG;
+      const bool valid = audioResponse &&
+        msg.udata == KVMFR_AUDIO_CONTROL_UDATA &&
+        msg.mem && msg.size == sizeof(response);
+      if (valid)
+        memcpy(&response, msg.mem, sizeof(response));
+      status = lgmpClientMessageDone(this->pointerQueue);
+      pthread_mutex_unlock(&this->pointerLock);
+      if (status != LGMP_OK)
+      {
+        printf("lgmpClientMessageDone: %s\n", lgmpStatusString(status));
+        break;
+      }
+      if (valid)
+        lgObsAudioHandleResponse(this->audio, &response);
+      else if (audioResponse)
+        blog(LOG_WARNING, "Ignoring malformed Looking Glass audio response");
+      continue;
+    }
+
     const KVMFRCursor * const cursor = (const KVMFRCursor * const)msg.mem;
     if (msg.udata & CURSOR_FLAG_VISIBLE_VALID)
     {
@@ -920,6 +967,8 @@ static void lgUpdate(void * data, obs_data_t * settings)
   LGPlugin * this = (LGPlugin *)data;
 
   deinit(this);
+  lgObsAudioSetEnabled(this->audio,
+      obs_data_get_bool(settings, "captureAudio"));
   this->shmFile = bstrdup(obs_data_get_string(settings, "shmFile"));
   if (!ivshmemOpenDev(&this->shmDev, this->shmFile))
     return;
@@ -974,6 +1023,9 @@ static void lgUpdate(void * data, obs_data_t * settings)
 
   lgFrameSchedulerInit(&this->frameScheduler,
     udata->features & KVMFR_FEATURE_FRAME_SCHEDULE, clientID);
+  if ((udata->features & KVMFR_FEATURE_AUDIO) &&
+      !lgObsAudioConnect(this->audio, this->lgmp, clientID))
+    blog(LOG_WARNING, "Failed to connect Looking Glass audio transport");
 
   this->state = STATE_STARTING;
   createThreads(this);
@@ -1738,6 +1790,7 @@ static void lgActivate(void * data)
   LGPlugin * this = (LGPlugin *)data;
   atomic_store_explicit(
     &this->sourceActive, true, memory_order_release);
+  lgObsAudioSetActive(this->audio, true);
 }
 
 static void lgDeactivate(void * data)
@@ -1745,6 +1798,7 @@ static void lgDeactivate(void * data)
   LGPlugin * this = (LGPlugin *)data;
   atomic_store_explicit(
     &this->sourceActive, false, memory_order_release);
+  lgObsAudioSetActive(this->audio, false);
 }
 
 static void lgSetupCursorEffect(LGPlugin * this, int outputTransfer)
@@ -1931,7 +1985,8 @@ struct obs_source_info lg_source =
 {
   .id                    = "looking-glass-obs",
   .type                  = OBS_SOURCE_TYPE_INPUT,
-  .output_flags          = OBS_SOURCE_VIDEO | OBS_SOURCE_CUSTOM_DRAW |
+  .output_flags          = OBS_SOURCE_VIDEO | OBS_SOURCE_AUDIO |
+                           OBS_SOURCE_CUSTOM_DRAW |
                            OBS_SOURCE_DO_NOT_DUPLICATE | OBS_SOURCE_SRGB,
   .get_name              = lgGetName,
   .create                = lgCreate,