Factor out data source

CHANGELOG.md

@@ -4,13 +4,13 @@ All notable changes to this project will be documented in this file.
 
 ---
 
-## [Master](https://github.com/fulldecent/FDWaveformView/compare/4.0.1...master)
+## [Master](https://github.com/fulldecent/FDWaveformView/compare/5.0.1...master)
 
 #### Changed
 
 ---
 
-## [4.0.1](https://github.com/fulldecent/FDWaveformView/releases/tag/4.0.1)
+## [5.0.1](https://github.com/fulldecent/FDWaveformView/releases/tag/5.0.1)
 Released on 2020-02-12.
 
 #### Changed
@@ -21,7 +21,7 @@ Released on 2020-02-12.
 
 ---
 
-## [4.0.0](https://github.com/fulldecent/FDWaveformView/releases/tag/4.0.0)
+## [5.0.0](https://github.com/fulldecent/FDWaveformView/releases/tag/5.0.0)
 Released on 2019-04-08.
 
 #### Changed

FDWaveformView.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name = 'FDWaveformView'
-  s.version = '4.0.1'
+  s.version = '5.0.1'
   s.license = { :type => 'MIT', :file => 'LICENSE' }
   s.summary = 'Reads an audio file and displays the waveform'
   s.description      = <<-DESC
@@ -9,7 +9,7 @@ DESC
   s.homepage         = 'https://github.com/fulldecent/FDWaveformView'
   s.screenshots      = 'https://camo.githubusercontent.com/8c51361597e3c150cce6f60db5055663a7a7f8f1/68747470733a2f2f692e696d6775722e636f6d2f354e376f7a6f672e706e67', 'https://camo.githubusercontent.com/3c21c8437f922ba6cb1a44b0701c02c140221d84/68747470733a2f2f692e696d6775722e636f6d2f665272486952502e706e67', 'https://camo.githubusercontent.com/771973985f42a25931bfafba291f313ba8e46e32/68747470733a2f2f692e696d6775722e636f6d2f4a514f4b51336f2e706e67', 'https://camo.githubusercontent.com/21e361bff1e2351a8f54636881c4290e4818501a/68747470733a2f2f692e696d6775722e636f6d2f386f52376370712e676966', 'https://camo.githubusercontent.com/700a0eeb4bfbf5bab688dcb11ef60784b2074eef/68747470733a2f2f692e696d6775722e636f6d2f456778586143592e676966'
   s.author           = { 'William Entriken' => '[email protected]' }
-  s.source           = { :git => 'https://github.com/fulldecent/FDWaveformView.git', :tag => s.version.to_s }
+  s.source           = { :git => 'https://github.com/fulldecent/FDWaveformView.git', :tag => "#{s.version}" }
   s.social_media_url = 'https://twitter.com/fulldecent'
   s.ios.deployment_target = '8.0'
   s.swift_version = '5.0'

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.1
+// swift-tools-version:5.3
 
 import PackageDescription
 

Sources/FDWaveformView/FDAudioSource.swift

@@ -0,0 +1,115 @@
+// Copyright 2013–2020, William Entriken and the FDWaveformView contributors.
+// Released under the MIT license as part of the FDWaveformView project.
+
+import Foundation
+import AVFoundation
+
+enum FDAudioSourceError: Error {
+    case FailedToReadTrackSamples
+}
+
+/// Reads samples from an audio file
+final class FDAudioSource: FDWaveformViewDataSource {
+
+    public let startIndex: Int = 0
+
+    public let endIndex: Int
+
+    /// Number of samples available
+    public let count: Int
+
+    /// The audio asset URL used to load the context
+    let audioURL: URL
+
+    /// Loaded asset
+    let asset: AVAsset
+
+    /// Loaded assetTrack
+    let assetTrack: AVAssetTrack
+
+    // MARK: - Initialization
+
+    // This is private beacuse details are not known until audio is asynchronously loaded
+    private init(audioURL: URL, totalSamples: Int, asset: AVAsset, assetTrack: AVAssetTrack) {
+        self.endIndex = totalSamples
+        self.audioURL = audioURL
+        self.asset = asset
+        self.assetTrack = assetTrack
+        count = endIndex - startIndex
+    }
+
+    /// Attempt to create collection of samples from an auedio track inside `audioURL`. This is a static function rather than a constructor because we run asynchronously.
+    /// - Parameters:
+    ///   - audioURL: A media file to load
+    ///   - completionHandler: The asynchronous callback (can call on any thread) and may possibly be called synchronousle
+    /// - Returns: Void
+    public static func load(fromAudioURL audioURL: URL, completionHandler: @escaping (_ audioContext: FDAudioSource?) -> ()) {
+        let assetOptions = [AVURLAssetPreferPreciseDurationAndTimingKey: NSNumber(value: true as Bool)]
+        let asset = AVURLAsset(url: audioURL, options: assetOptions)
+        guard let assetTrack = asset.tracks(withMediaType: .audio).first else
+        {
+            NSLog("FDWaveformView failed to load AVAssetTrack audio track")
+            completionHandler(nil)
+            return
+        }
+
+        asset.loadValuesAsynchronously(forKeys: ["duration"]) {
+            var error: NSError?
+            if asset.statusOfValue(forKey: "duration", error: &error) == .loaded {
+                let totalSamples = Int(Float64(assetTrack.naturalTimeScale) * Float64(asset.duration.value) / Float64(asset.duration.timescale))
+                completionHandler(Self.init(audioURL: audioURL, totalSamples: totalSamples, asset: asset, assetTrack: assetTrack))
+                return
+            }
+            print("FDWaveformView could not load asset: \(error?.localizedDescription ?? "Unknown error")")
+            completionHandler(nil)
+        }
+    }
+
+    // MARK: - Features
+
+    /// Get audio sample data
+    /// - Parameter bounds: These are in units of the `assetTrack`'s natural timescale, as is startIndex and endIndex
+    /// - Throws:FDAudioSourceError
+    /// - Returns: 16-bit data values (2 bytes per sample)
+    func readSampleData(bounds: Range<Int>) throws -> Data {
+        //TODO: Consider outputting [Float] directly here. Then possible this could conform to RandomAccessCollection
+        let assetReader = try AVAssetReader(asset: asset) // AVAssetReader is a one-shot reader so we cannot make it a class property
+        assetReader.timeRange = CMTimeRange(start: CMTime(value: Int64(bounds.lowerBound), timescale: assetTrack.naturalTimeScale),
+                                       duration: CMTime(value: Int64(bounds.count), timescale: assetTrack.naturalTimeScale))
+        let outputSettingsDict: [String : Any] = [
+            AVFormatIDKey: Int(kAudioFormatLinearPCM),
+            AVLinearPCMBitDepthKey: 16,
+            AVLinearPCMIsBigEndianKey: false,
+            AVLinearPCMIsFloatKey: false, // TODO: Maybe use float here because we convert using DSP later anyway. Need to profile performance of this change.
+            AVLinearPCMIsNonInterleaved: false
+        ]
+
+        let readerOutput = AVAssetReaderTrackOutput(track: assetTrack, outputSettings: outputSettingsDict)
+        readerOutput.alwaysCopiesSampleData = false
+        assetReader.add(readerOutput)
+
+        var sampleBuffer = Data() // 16-bit samples
+        assetReader.startReading()
+        defer { assetReader.cancelReading() } // Cancel reading if we exit early or if operation is cancelled
+
+        while assetReader.status == .reading {
+            guard let readSampleBuffer = readerOutput.copyNextSampleBuffer(),
+                  let readBuffer = CMSampleBufferGetDataBuffer(readSampleBuffer) else {
+                break
+            }
+            // Append audio sample buffer into our current sample buffer
+            var readBufferLength: Int = 0
+            var readBufferPointer: UnsafeMutablePointer<Int8>?
+            CMBlockBufferGetDataPointer(readBuffer, atOffset: 0, lengthAtOffsetOut: &readBufferLength, totalLengthOut: nil, dataPointerOut: &readBufferPointer)
+            sampleBuffer.append(UnsafeBufferPointer(start: readBufferPointer, count: readBufferLength))
+            CMSampleBufferInvalidate(readSampleBuffer)
+        }
+
+        // if (reader.status == AVAssetReaderStatusFailed || reader.status == AVAssetReaderStatusUnknown)
+        // Something went wrong. Handle it or do not, depending on if you can get above to work
+        if assetReader.status == .completed {
+            return sampleBuffer
+        }
+        throw FDAudioSourceError.FailedToReadTrackSamples
+    }
+}