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  3. FAudioChunkCache

FAudioChunkCache

Basic fixed-size LRU cache for retaining chunks of compressed audio data.

API > API/Runtime > API/Runtime/Engine

Basic fixed-size LRU cache for retaining chunks of compressed audio data.

   
Name FAudioChunkCache
Type class
Header File /Engine/Source/Runtime/Engine/Public/AudioStreamingCache.h
Include Path #include "AudioStreamingCache.h"

Syntax

class FAudioChunkCache

Constructors

Name Remarks Include Path Unreal Specifiers

FAudioChunkCache ( uint32 InMaxChunkSize,
uint32 NumChunks,
uint64 InMemoryLimitInBytes
)

   AudioStreamingCache.h  

Destructors

Name Remarks Include Path Unreal Specifiers

~FAudioChunkCache()

   AudioStreamingCache.h  

Structs

Name Remarks
FCacheElement Struct containing a single element in our LRU Cache.
FCacheElementDebugInfo This struct lets us breadcrumb debug information.
FCacheMissEntry  
FCacheMissInfo This struct is used for logging cache misses.
FChunkKey  
FSoundWaveMemoryTracker  

Enums

Public

Name Remarks
EDebugDisplayElementTypes This is for debugging purposes only.

Variables

Public

Name Type Remarks Include Path Unreal Specifiers
MaxChunkSize const int32   AudioStreamingCache.h  

Protected

Name Type Remarks Include Path Unreal Specifiers
bLogCacheMisses bool This is set to true when BeginLoggingCacheMisses is called. AudioStreamingCache.h  
CacheLookupIdMap TMap< FChunkKey, uint64 > Map that USoundWaves, FSoundWaveProxys, FChunkKeys, and FAudioChunkHandles can use to quickly lookup where their chunks are currently stored in the cache AudioStreamingCache.h  
CacheMissQueue TUniqueObj< TQueue< FCacheMissInfo > > This queue is pushed to anytime GetChunk fails to get the chunk. and bLogCacheMisses is true. AudioStreamingCache.h  
CacheMutationCriticalSection TDontCopy< FCriticalSection > Critical section: only used when we are modifying element positions in the cache. AudioStreamingCache.h  
CacheOverflowCount FThreadSafeCounter Counter for the number of times this cache has overflown AudioStreamingCache.h  
CachePool TArray< FCacheElement > Our actual memory pool. AudioStreamingCache.h  
ChunksInUse int32 This is incremented on every call of InsertChunk until we hit CachePool.Num() or MemoryCounterBytes hits MemoryLimitBytes. AudioStreamingCache.h  
FeatureMemoryCounterBytes TUniqueObj< TAtomic< uint64 > >   AudioStreamingCache.h  
ForceInlineMemoryCounterBytes TUniqueObj< TAtomic< uint64 > >   AudioStreamingCache.h  
LeastRecentElement FCacheElement *   AudioStreamingCache.h  
MemoryCounterBytes TUniqueObj< TAtomic< uint64 > > This counter is used to start evicting chunks before we hit CachePool.Num(). AudioStreamingCache.h  
MemoryLimitBytes uint64   AudioStreamingCache.h  
MostRecentElement FCacheElement *   AudioStreamingCache.h  
NumberOfLoadsInFlight FThreadSafeCounter Number of async load operations we have currently in flight. AudioStreamingCache.h  
SoundWaveMemoryTrackerCritSec TDontCopy< FCriticalSection >   AudioStreamingCache.h  
SoundWaveTracker TMap< FSoundWaveProxyPtr, FSoundWaveMemoryTracker > A map to look up the number of times a sound wave has been added for memory tracking as well as the memory added for the "latest" addition AudioStreamingCache.h  
TimeOfBeginPlayCycles uint64 Time begin play came in. (so we can validate load times against load screen/vs level loads). AudioStreamingCache.h  

Functions

Public

Name Remarks Include Path Unreal Specifiers

void AddForceInlineSoundWave ( const FSoundWaveProxyPtr&
)

   AudioStreamingCache.h  

void AddMemoryCountedFeature ( const FAudioStreamCacheMemoryHandle& Feature
)

   AudioStreamingCache.h  

void AddNewReferenceToChunk ( const FChunkKey& InKey
)

 Add an additional reference for a chunk. AudioStreamingCache.h  

uint64 AddOrTouchChunk ( const FChunkKey& InKey,
const TSharedPtr< FSoundWaveData >& InSoundWavePtr,
TFunction< void(EAudioChunkLoadResult) > OnLoadCompleted,
ENamedThreads::Type CallbackThread,
bool bNeededForPlayback
)

 Places chunk in cache, or puts this chunk back at the top of the cache if it's already loaded. AudioStreamingCache.h  
Debug tools: Call this to start enqueing reports on any cache misses to a queue. AudioStreamingCache.h  

void BlockForAllPendingLoads()

 This function will continue to lock until any async file loads are finished. AudioStreamingCache.h  

void CancelAllPendingLoads()

 This function will cancel any in-flight loads and wait for their completion. AudioStreamingCache.h  

void ClearCache()

 Evict all sounds from the cache. Does not account for force inline sounds. AudioStreamingCache.h  

TPair< int, int > DebugBirdsEyeDisplay ( UWorld* World,
FViewport* Viewport,
FCanvas* Canvas,
int32 X,
int32 Y,
const FVector* ViewLocation,
const FRotator* ViewRotation
) const

   AudioStreamingCache.h  

TPair< int, int > DebugDisplay ( UWorld* World,
FViewport* Viewport,
FCanvas* Canvas,
int32 X,
int32 Y,
const FVector* ViewLocation,
const FRotator* ViewRotation
) const

   AudioStreamingCache.h  

TPair< int, int > DebugDisplayLegacy ( UWorld* World,
FViewport* Viewport,
FCanvas* Canvas,
int32 X,
int32 Y,
const FVector* ViewLocation,
const FRotator* ViewRotation
) const

 This is for debugging purposes only. AudioStreamingCache.h  

FString DebugPrint()

 Generate a formatted text file for this cache. AudioStreamingCache.h  

TPair< int, int > DebugVisualDisplay ( UWorld* World,
FViewport* Viewport,
FCanvas* Canvas,
int32 X,
int32 Y,
const FVector* ViewLocation,
const FRotator* ViewRotation
) const

   AudioStreamingCache.h  

FString FlushCacheMissLog()

 When called, flushes the entire queue of cache misses that has accumulated And prints them to a formatted AudioStreamingCache.h  

uint64 GetCacheLookupIDForChunk ( const FChunkKey& InChunkKey
) const

 Interface with the cache id lookup map AudioStreamingCache.h  

TArrayView< uint8 > GetChunk ( const FChunkKey& InKey,
const TSharedPtr< FSoundWaveData >& InSoundWavePtr,
bool bBlockForLoadCompletion,
bool bNeededForPlayback,
uint64& InOutCacheLookupID
)

 Returns the chunk asked for, or an empty TArrayView if that chunk is not loaded. AudioStreamingCache.h  

TArray< FObjectKey > GetLeastRecentlyUsedRetainedSoundWaves ( int32 NumSoundWavesToRetrieve
)

 Returns an array of the USoundwaves retaining the least recently used retained chunks in the cache. AudioStreamingCache.h  

int32 GetNumberOfCacheOverflows()

   AudioStreamingCache.h  

void HandleStarvation ( const FSoundWaveProxyPtr& SoundWave,
const uint32 ChunkIndex,
const uint32 InBytesProduced,
const uint32 InBytesExpected
)

   AudioStreamingCache.h  

void IncrementCacheOverflowCounter()

   AudioStreamingCache.h  

void RemoveForceInlineSoundWave ( const FSoundWaveProxyPtr&
)

   AudioStreamingCache.h  

void RemoveMemoryCountedFeature ( const FAudioStreamCacheMemoryHandle& Feature
)

   AudioStreamingCache.h  

void RemoveReferenceToChunk ( const FChunkKey& InKey
)

   AudioStreamingCache.h  

uint64 ReportCacheSize()

 Reports the size of this cache's memory pool, in bytes. AudioStreamingCache.h  

void SetCacheLookupIDForChunk ( const FChunkKey& InChunkKey,
uint64 InCacheLookupID
)

   AudioStreamingCache.h  

void StopLoggingCacheMisses()

 This will stop enqueueing reports of cache misses. AudioStreamingCache.h  

uint64 TrimMemory ( uint64 BytesToFree,
bool bAllowRetainedChunkTrimming
)

 This function will reclaim memory by freeing as many chunks as needed to free BytesToFree. AudioStreamingCache.h  

Static

Name Remarks Include Path Unreal Specifiers

static bool DoesKeyContainValidChunkIndex ( const FChunkKey& InKey,
const FSoundWaveData& InSoundWaveData
)

 Static helper function to make sure a chunk is withing the bounds of a USoundWave. AudioStreamingCache.h  

static void ExecuteOnLoadCompleteCallback ( EAudioChunkLoadResult Result,
const TFunction< void(EAudioChunkLoadResult)>& OnLoadCompleted,
const ENamedThreads::Type& CallbackThread
)

 Calls OnLoadCompleted on current thread if CallbackThread == ENamedThreads::AnyThread, and dispatchs an async task on a named thread otherwise. AudioStreamingCache.h  

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