Example app VAD default + memory reduction (#217)

* Release memory when transcribing single files

Co-authored-by: keleftheriou <keleftheriou@users.noreply.github.com>

* Add method to load from file into float array iteratively

- Reduces peak memory by doing the array conversion while loading in chunks so the array copy size is lower
- Previously copied the entire buffer which spiked the memory 2x

* Fix leak

* Use vad by default in examples

* Fix vad thread issue

* Fix unused warning

* Revert change to early stop callback

* Fix warnings

- Optional cli commands are deprecated
- @_disfavoredOverload required @available to prevent infinite loop

* PR review - simplify early stop test logic

Co-authored-by: Andrey Leonov <aleonov@gmail.com>

* Cleanup from review

---------

Co-authored-by: keleftheriou <keleftheriou@users.noreply.github.com>
Co-authored-by: Andrey Leonov <aleonov@gmail.com>

Examples/WhisperAX/WhisperAX/Views/ContentView.swift

@@ -51,7 +51,8 @@ struct ContentView: View {
     @AppStorage("silenceThreshold") private var silenceThreshold: Double = 0.3
     @AppStorage("useVAD") private var useVAD: Bool = true
     @AppStorage("tokenConfirmationsNeeded") private var tokenConfirmationsNeeded: Double = 2
-    @AppStorage("chunkingStrategy") private var chunkingStrategy: ChunkingStrategy = .none
+    @AppStorage("concurrentWorkerCount") private var concurrentWorkerCount: Int = 4
+    @AppStorage("chunkingStrategy") private var chunkingStrategy: ChunkingStrategy = .vad
     @AppStorage("encoderComputeUnits") private var encoderComputeUnits: MLComputeUnits = .cpuAndNeuralEngine
     @AppStorage("decoderComputeUnits") private var decoderComputeUnits: MLComputeUnits = .cpuAndNeuralEngine
 
@@ -1269,12 +1270,15 @@ struct ContentView: View {
 
     func transcribeCurrentFile(path: String) async throws {
         // Load and convert buffer in a limited scope
+        Logging.debug("Loading audio file: \(path)")
+        let loadingStart = Date()
         let audioFileSamples = try await Task {
             try autoreleasepool {
-                let audioFileBuffer = try AudioProcessor.loadAudio(fromPath: path)
-                return AudioProcessor.convertBufferToArray(buffer: audioFileBuffer)
+                return try AudioProcessor.loadAudioAsFloatArray(fromPath: path)
             }
         }.value
+        Logging.debug("Loaded audio file in \(Date().timeIntervalSince(loadingStart)) seconds")
+
 
         let transcription = try await transcribeAudioSamples(audioFileSamples)
 
@@ -1316,6 +1320,7 @@ struct ContentView: View {
             withoutTimestamps: !enableTimestamps,
             wordTimestamps: true,
             clipTimestamps: seekClip,
+            concurrentWorkerCount: concurrentWorkerCount,
             chunkingStrategy: chunkingStrategy
         )
 

Sources/WhisperKit/Core/Audio/AudioChunker.swift

@@ -81,7 +81,6 @@ open class VADAudioChunker: AudioChunking {
             // Typically this will be the full audio file, unless seek points are explicitly provided
             var startIndex = seekClipStart
             while startIndex < seekClipEnd - windowPadding {
-                let currentFrameLength = audioArray.count
                 guard startIndex >= 0 && startIndex < audioArray.count else {
                     throw WhisperError.audioProcessingFailed("startIndex is outside the buffer size")
                 }

Sources/WhisperKit/Core/Audio/AudioProcessor.swift

@@ -93,8 +93,6 @@ public extension AudioProcessing {
     }
 
     static func padOrTrimAudio(fromArray audioArray: [Float], startAt startIndex: Int = 0, toLength frameLength: Int = 480_000, saveSegment: Bool = false) -> MLMultiArray? {
-        let currentFrameLength = audioArray.count
-
         guard startIndex >= 0 && startIndex < audioArray.count else {
             Logging.error("startIndex is outside the buffer size")
             return nil
@@ -197,7 +195,15 @@ public class AudioProcessor: NSObject, AudioProcessing {
 
         let audioFileURL = URL(fileURLWithPath: audioFilePath)
         let audioFile = try AVAudioFile(forReading: audioFileURL, commonFormat: .pcmFormatFloat32, interleaved: false)
+        return try loadAudio(fromFile: audioFile, startTime: startTime, endTime: endTime, maxReadFrameSize: maxReadFrameSize)
+    }
 
+    public static func loadAudio(
+        fromFile audioFile: AVAudioFile,
+        startTime: Double? = 0,
+        endTime: Double? = nil,
+        maxReadFrameSize: AVAudioFrameCount? = nil
+    ) throws -> AVAudioPCMBuffer {
         let sampleRate = audioFile.fileFormat.sampleRate
         let channelCount = audioFile.fileFormat.channelCount
         let frameLength = AVAudioFrameCount(audioFile.length)
@@ -243,13 +249,56 @@ public class AudioProcessor: NSObject, AudioProcessing {
         }
     }
 
+    public static func loadAudioAsFloatArray(
+        fromPath audioFilePath: String,
+        startTime: Double? = 0,
+        endTime: Double? = nil
+    ) throws -> [Float] {
+        guard FileManager.default.fileExists(atPath: audioFilePath) else {
+            throw WhisperError.loadAudioFailed("Resource path does not exist \(audioFilePath)")
+        }
+
+        let audioFileURL = URL(fileURLWithPath: audioFilePath)
+        let audioFile = try AVAudioFile(forReading: audioFileURL, commonFormat: .pcmFormatFloat32, interleaved: false)
+        let inputSampleRate = audioFile.fileFormat.sampleRate
+        let inputFrameCount = AVAudioFrameCount(audioFile.length)
+        let inputDuration = Double(inputFrameCount) / inputSampleRate
+
+        let start = startTime ?? 0
+        let end = min(endTime ?? inputDuration, inputDuration)
+
+        // Load 10m of audio at a time to reduce peak memory while converting
+        // Particularly impactful for large audio files
+        let chunkDuration: Double = 60 * 10
+        var currentTime = start
+        var result: [Float] = []
+
+        while currentTime < end {
+            let chunkEnd = min(currentTime + chunkDuration, end)
+
+            try autoreleasepool {
+                let buffer = try loadAudio(
+                    fromFile: audioFile,
+                    startTime: currentTime,
+                    endTime: chunkEnd
+                )
+
+                let floatArray = Self.convertBufferToArray(buffer: buffer)
+                result.append(contentsOf: floatArray)
+            }
+
+            currentTime = chunkEnd
+        }
+
+        return result
+    }
+
     public static func loadAudio(at audioPaths: [String]) async -> [Result<[Float], Swift.Error>] {
         await withTaskGroup(of: [(index: Int, result: Result<[Float], Swift.Error>)].self) { taskGroup -> [Result<[Float], Swift.Error>] in
             for (index, audioPath) in audioPaths.enumerated() {
                 taskGroup.addTask {
                     do {
-                        let audioBuffer = try AudioProcessor.loadAudio(fromPath: audioPath)
-                        let audio = AudioProcessor.convertBufferToArray(buffer: audioBuffer)
+                        let audio = try AudioProcessor.loadAudioAsFloatArray(fromPath: audioPath)
                         return [(index: index, result: .success(audio))]
                     } catch {
                         return [(index: index, result: .failure(error))]
@@ -280,10 +329,10 @@ public class AudioProcessor: NSObject, AudioProcessing {
         frameCount: AVAudioFrameCount? = nil,
         maxReadFrameSize: AVAudioFrameCount = Constants.defaultAudioReadFrameSize
     ) -> AVAudioPCMBuffer? {
-        let inputFormat = audioFile.fileFormat
+        let inputSampleRate = audioFile.fileFormat.sampleRate
         let inputStartFrame = audioFile.framePosition
         let inputFrameCount = frameCount ?? AVAudioFrameCount(audioFile.length)
-        let inputDuration = Double(inputFrameCount) / inputFormat.sampleRate
+        let inputDuration = Double(inputFrameCount) / inputSampleRate
         let endFramePosition = min(inputStartFrame + AVAudioFramePosition(inputFrameCount), audioFile.length + 1)
 
         guard let outputFormat = AVAudioFormat(standardFormatWithSampleRate: sampleRate, channels: channelCount) else {
@@ -305,8 +354,8 @@ public class AudioProcessor: NSObject, AudioProcessing {
             let remainingFrames = AVAudioFrameCount(endFramePosition - audioFile.framePosition)
             let framesToRead = min(remainingFrames, maxReadFrameSize)
 
-            let currentPositionInSeconds = Double(audioFile.framePosition) / inputFormat.sampleRate
-            let nextPositionInSeconds = (Double(audioFile.framePosition) + Double(framesToRead)) / inputFormat.sampleRate
+            let currentPositionInSeconds = Double(audioFile.framePosition) / inputSampleRate
+            let nextPositionInSeconds = (Double(audioFile.framePosition) + Double(framesToRead)) / inputSampleRate
             Logging.debug("Resampling \(String(format: "%.2f", currentPositionInSeconds))s - \(String(format: "%.2f", nextPositionInSeconds))s")
 
             do {
@@ -644,7 +693,7 @@ public class AudioProcessor: NSObject, AudioProcessing {
                 &propertySize,
                 &name
             )
-            if status == noErr, let deviceNameCF = name?.takeUnretainedValue() as String? {
+            if status == noErr, let deviceNameCF = name?.takeRetainedValue() as String? {
                 deviceName = deviceNameCF
             }
 

Sources/WhisperKit/Core/TextDecoder.swift

@@ -591,9 +591,11 @@ open class TextDecoder: TextDecoding, WhisperMLModel {
         var hasAlignment = false
         var isFirstTokenLogProbTooLow = false
         let windowUUID = UUID()
-        DispatchQueue.global().async { [weak self] in
+        Task { [weak self] in
             guard let self = self else { return }
-            self.shouldEarlyStop[windowUUID] = false
+            await MainActor.run {
+                self.shouldEarlyStop[windowUUID] = false
+            }
         }
         for tokenIndex in prefilledIndex..<loopCount {
             let loopStart = Date()

Sources/WhisperKit/Core/Utils.swift

@@ -205,6 +205,14 @@ public extension String {
 }
 
 extension AVAudioPCMBuffer {
+    /// Converts the buffer to a float array
+    func asFloatArray() throws -> [Float] {
+        guard let data = floatChannelData?.pointee else {
+            throw WhisperError.audioProcessingFailed("Error converting audio, missing floatChannelData")
+        }
+        return Array(UnsafeBufferPointer(start: data, count: Int(frameLength)))
+    }
+
     /// Appends the contents of another buffer to the current buffer
     func appendContents(of buffer: AVAudioPCMBuffer) -> Bool {
         return appendContents(of: buffer, startingFrame: 0, frameCount: buffer.frameLength)
@@ -446,8 +454,9 @@ public func modelSupport(for deviceName: String, from config: ModelSupportConfig
 /// Deprecated
 @available(*, deprecated, message: "Subject to removal in a future version. Use modelSupport(for:from:) -> ModelSupport instead.")
 @_disfavoredOverload
+@available(macOS 13, iOS 16, watchOS 10, visionOS 1, *)
 public func modelSupport(for deviceName: String, from config: ModelSupportConfig? = nil) -> (default: String, disabled: [String]) {
-    let modelSupport = modelSupport(for: deviceName, from: config)
+    let modelSupport: ModelSupport = modelSupport(for: deviceName, from: config)
     return (modelSupport.default, modelSupport.disabled)
 }
 

Sources/WhisperKit/Core/WhisperKit.swift

@@ -446,7 +446,8 @@ open class WhisperKit {
     open func detectLanguage(
         audioPath: String
     ) async throws -> (language: String, langProbs: [String: Float]) {
-        let audioBuffer = try AudioProcessor.loadAudio(fromPath: audioPath)
+        // Only need the first 30s for language detection
+        let audioBuffer = try AudioProcessor.loadAudio(fromPath: audioPath, endTime: 30.0)
         let audioArray = AudioProcessor.convertBufferToArray(buffer: audioBuffer)
         return try await detectLangauge(audioArray: audioArray)
     }
@@ -721,15 +722,17 @@ open class WhisperKit {
         callback: TranscriptionCallback = nil
     ) async throws -> [TranscriptionResult] {
         // Process input audio file into audio samples
-        let loadAudioStart = Date()
-        let audioBuffer = try AudioProcessor.loadAudio(fromPath: audioPath)
-        let loadTime = Date().timeIntervalSince(loadAudioStart)
+        let audioArray = try await withThrowingTaskGroup(of: [Float].self) { group -> [Float] in
+            let convertAudioStart = Date()
+            defer {
+                let convertTime = Date().timeIntervalSince(convertAudioStart)
+                currentTimings.audioLoading = convertTime
+                Logging.debug("Audio loading and convert time: \(convertTime)")
+                logCurrentMemoryUsage("Audio Loading and Convert")
+            }
 
-        let convertAudioStart = Date()
-        let audioArray = AudioProcessor.convertBufferToArray(buffer: audioBuffer)
-        let convertTime = Date().timeIntervalSince(convertAudioStart)
-        currentTimings.audioLoading = loadTime + convertTime
-        Logging.debug("Audio loading time: \(loadTime), Audio convert time: \(convertTime)")
+            return try AudioProcessor.loadAudioAsFloatArray(fromPath: audioPath)
+        }
 
         let transcribeResults: [TranscriptionResult] = try await transcribe(
             audioArray: audioArray,
@@ -837,23 +840,23 @@ open class WhisperKit {
             throw WhisperError.tokenizerUnavailable()
         }
 
-        let childProgress = Progress()
-        progress.totalUnitCount += 1
-        progress.addChild(childProgress, withPendingUnitCount: 1)
-
-        let transcribeTask = TranscribeTask(
-            currentTimings: currentTimings,
-            progress: childProgress,
-            audioEncoder: audioEncoder,
-            featureExtractor: featureExtractor,
-            segmentSeeker: segmentSeeker,
-            textDecoder: textDecoder,
-            tokenizer: tokenizer
-        )
-
         do {
             try Task.checkCancellation()
 
+            let childProgress = Progress()
+            progress.totalUnitCount += 1
+            progress.addChild(childProgress, withPendingUnitCount: 1)
+
+            let transcribeTask = TranscribeTask(
+                currentTimings: currentTimings,
+                progress: childProgress,
+                audioEncoder: audioEncoder,
+                featureExtractor: featureExtractor,
+                segmentSeeker: segmentSeeker,
+                textDecoder: textDecoder,
+                tokenizer: tokenizer
+            )
+
             let transcribeTaskResult = try await transcribeTask.run(
                 audioArray: audioArray,
                 decodeOptions: decodeOptions,

Sources/WhisperKitCLI/CLIArguments.swift

@@ -103,9 +103,9 @@ struct CLIArguments: ParsableArguments {
     @Flag(help: "Simulate streaming transcription using the input audio file")
     var streamSimulated: Bool = false
 
-    @Option(help: "Maximum concurrent inference, might be helpful when processing more than 1 audio file at the same time. 0 means unlimited")
-    var concurrentWorkerCount: Int = 0
+    @Option(help: "Maximum concurrent inference, might be helpful when processing more than 1 audio file at the same time. 0 means unlimited. Default: 4")
+    var concurrentWorkerCount: Int = 4
 
-    @Option(help: "Chunking strategy for audio processing, `nil` means no chunking, `vad` means using voice activity detection")
-    var chunkingStrategy: String? = nil
+    @Option(help: "Chunking strategy for audio processing, `none` means no chunking, `vad` means using voice activity detection. Default: `vad`")
+    var chunkingStrategy: String = "vad"
 }

Sources/WhisperKitCLI/TranscribeCLI.swift

@@ -38,10 +38,8 @@ struct TranscribeCLI: AsyncParsableCommand {
             cliArguments.audioPath = audioFiles.map { audioFolder + "/" + $0 }
         }
 
-        if let chunkingStrategyRaw = cliArguments.chunkingStrategy {
-            if ChunkingStrategy(rawValue: chunkingStrategyRaw) == nil {
-                throw ValidationError("Wrong chunking strategy \"\(chunkingStrategyRaw)\", valid strategies: \(ChunkingStrategy.allCases.map { $0.rawValue })")
-            }
+        if ChunkingStrategy(rawValue: cliArguments.chunkingStrategy) == nil {
+            throw ValidationError("Wrong chunking strategy \"\(cliArguments.chunkingStrategy)\", valid strategies: \(ChunkingStrategy.allCases.map { $0.rawValue })")
         }
     }
 
@@ -318,12 +316,6 @@ struct TranscribeCLI: AsyncParsableCommand {
     }
 
     private func decodingOptions(task: DecodingTask) -> DecodingOptions {
-        let chunkingStrategy: ChunkingStrategy? =
-            if let chunkingStrategyRaw = cliArguments.chunkingStrategy {
-                ChunkingStrategy(rawValue: chunkingStrategyRaw)
-            } else {
-                nil
-            }
         return DecodingOptions(
             verbose: cliArguments.verbose,
             task: task,
@@ -344,7 +336,7 @@ struct TranscribeCLI: AsyncParsableCommand {
             firstTokenLogProbThreshold: cliArguments.firstTokenLogProbThreshold,
             noSpeechThreshold: cliArguments.noSpeechThreshold ?? 0.6,
             concurrentWorkerCount: cliArguments.concurrentWorkerCount,
-            chunkingStrategy: chunkingStrategy
+            chunkingStrategy: ChunkingStrategy(rawValue: cliArguments.chunkingStrategy)
         )
     }
 

Tests/WhisperKitTests/UnitTests.swift

@@ -548,9 +548,11 @@ final class UnitTests: XCTestCase {
     }
 
     func testDecodingEarlyStopping() async throws {
+        let earlyStopTokenCount = 10
         let options = DecodingOptions()
         let continuationCallback: TranscriptionCallback = { (progress: TranscriptionProgress) -> Bool? in
-            false
+            // Stop after only 10 tokens (full test audio contains 16)
+            return progress.tokens.count <= earlyStopTokenCount
         }
 
         let result = try await XCTUnwrapAsync(
@@ -576,6 +578,7 @@ final class UnitTests: XCTestCase {
         XCTAssertNotNil(resultWithWait)
         let tokenCountWithWait = resultWithWait.segments.flatMap { $0.tokens }.count
         let decodingTimePerTokenWithWait = resultWithWait.timings.decodingLoop / Double(tokenCountWithWait)
+        Logging.debug("Decoding loop without wait: \(result.timings.decodingLoop), with wait: \(resultWithWait.timings.decodingLoop)")
 
         // Assert that the decoding predictions per token are not slower with the waiting
         XCTAssertEqual(decodingTimePerTokenWithWait, decodingTimePerToken, accuracy: decodingTimePerToken, "Decoding predictions per token should not be significantly slower with waiting")