Reword caching to prefetching

Since that makes it much clearer what we're actually doing. With old
`cache_time_info` was actually caching the response, but now we're
querying it before the plugin has even requested the information.

CHANGELOG.md

@@ -10,17 +10,19 @@ Versioning](https://semver.org/spec/v2.0.0.html).
 
 ### Added
 
-- During VST2 audio processing calls, yabridge will now immediately send the
-  current transport information along with the audio buffers. This lets us cache
-  this information during the processing call, which significantly reduce the
-  overhead of bridging VST2 plugins by avoiding one otherwise mandatory back and
-  forth function call between yabridge's plugin and the Wine plugin host. This
-  has an even greater impact on plugins like _SWAM Cello_ that request this
-  information repeatedly for every sample they process. Previously yabridge had
-  a `cache_time_info` compatibility option to mitigate the performance hit for
-  those plugins, but this new caching behaviour supercedes that.
-- Similarly, yabridge will also cache the current process level during audio
-  processing to reduce bridging overhead for plugins that use this.
+- During VST2 audio processing calls, yabridge will now prefetch the current
+  transport information and send that to the Wine plugin host along with the
+  audio buffers. This lets us cache this information during the processing call,
+  which significantly reduces the overhead of bridging VST2 plugins by avoiding
+  one otherwise mandatory back and forth function call between yabridge's plugin
+  and the Wine plugin host. This has an even greater impact on plugins like
+  _SWAM Cello_ that request this information repeatedly over the course of a
+  single audio processing cycle. Previously yabridge had a `cache_time_info`
+  compatibility option to mitigate the performance hit for those plugins, but
+  this new caching behaviour supercedes that.
+- Similarly, yabridge will also prefetch the current process level during audio
+  processing to reduce bridging overhead for plugins that use this, like the
+  _Meldaproduction_ plugins.
 - We now always force the CPU's flush-to-zero flag to be set when processing
   audio. Most plugins will already do this themselves, but plugins like _Kush
   Audio REDDI_ and _Expressive E Noisy_ that don't will otherwise suffer from

src/common/serialization/vst2.h

@@ -556,16 +556,16 @@ struct AudioBuffers {
     int sample_frames;
 
     /**
-     * We'll send the current transport information as part of an audio
-     * processing call. This lets us a void an unnecessary callback (or in some
-     * cases, more than one) during every processing cycle.
+     * We'll prefetch the current transport information as part of handling an
+     * audio processing call. This lets us a void an unnecessary callback (or in
+     * some cases, more than one) during every processing cycle.
      */
     std::optional<VstTimeInfo> current_time_info;
 
     /**
      * Some plugins will also ask for the current process level during audio
-     * processing. To prevent unnecessary expensive callbacks, we'll send this
-     * information along with the processing call.
+     * processing. To prevent unnecessary expensive callbacks there, we'll
+     * prefetch this information as well.
      */
     int current_process_level;
 

src/plugin/bridges/vst2.cpp

@@ -568,8 +568,8 @@ void Vst2PluginBridge::do_process(T** inputs, T** outputs, int sample_frames) {
         current_time_info = *returned_time_info;
     }
 
-    // Some plugisn also ask for the current process level, so we'll cache that
-    // information as well
+    // Some plugisn also ask for the current process level, so we'll prefetch
+    // that information as well
     const int current_process_level = static_cast<int>(host_callback_function(
         &plugin, audioMasterGetCurrentProcessLevel, 0, 0, nullptr, 0.0));
     if (returned_time_info) {

src/wine-host/bridges/vst2.cpp

@@ -188,7 +188,7 @@ Vst2Bridge::Vst2Bridge(MainContext& main_context,
             [&](AudioBuffers request, std::vector<uint8_t>& buffer) {
                 // Since the value cannot change during this processing cycle,
                 // we'll send the current transport information as part of the
-                // request so we cache it to avoid unnecessary callbacks from
+                // request so we prefetch it to avoid unnecessary callbacks from
                 // the audio thread
                 std::optional<decltype(time_info_cache)::Guard>
                     time_info_cache_guard =
@@ -197,8 +197,8 @@ Vst2Bridge::Vst2Bridge(MainContext& main_context,
                                   *request.current_time_info))
                             : std::nullopt;
 
-                // We'll also cache the process level, since some plugins will
-                // ask for this during every processing cycle
+                // We'll also prefetch the process level, since some plugins
+                // will ask for this during every processing cycle
                 decltype(process_level_cache)::Guard process_level_cache_guard =
                     process_level_cache.set(request.current_process_level);
 

src/wine-host/bridges/vst2.h

@@ -114,8 +114,8 @@ class Vst2Bridge : public HostBridge {
      * We'll store the last transport information obtained from the host as a
      * result of `audioMasterGetTime()` here so we can return a pointer to it if
      * the request was successful. To prevent unnecessary back and forth
-     * communication, we'll send a copy of the current transport information to
-     * the plugin as part of the audio processing call.
+     * communication, we'll prefetch the current transport information in the
+     * plugin as part of the audio processing call.
      *
      * @see cached_time_info
      */
@@ -131,7 +131,7 @@ class Vst2Bridge : public HostBridge {
 
     /**
      * Some plugins will also ask for the current process level during audio
-     * processing, so we'll also cache that to prevent expensive callbacks.
+     * processing, so we'll also prefetch that to prevent expensive callbacks.
      */
     ScopedValueCache<int> process_level_cache;