Merge branch 'master' of github.com:fulldecent/FDWaveformView

Author: fulldecent

CHANGELOG.md

@@ -16,6 +16,8 @@ Released on 2020-02-12.
 #### Changed
 - Switch to new standard library clamp functions
   - Added by [William Entriken](https://github.com/fulldecent)
+- Fixed timescale bug for some mp4 files
+  - Added by [Doug Earnshaw](https://github.com/pixlwave)
 
 ---
 

Sources/FDWaveformView/FDWaveformRenderOperation.swift

@@ -151,8 +151,17 @@ final public class FDWaveformRenderOperation: Operation {
             let reader = try? AVAssetReader(asset: audioContext.asset)
             else { return nil }
 
-        reader.timeRange = CMTimeRange(start: CMTime(value: Int64(slice.lowerBound), timescale: audioContext.asset.duration.timescale),
-                                       duration: CMTime(value: Int64(slice.count), timescale: audioContext.asset.duration.timescale))
+        var channelCount = 1
+        var sampleRate: CMTimeScale = 44100
+        let formatDescriptions = audioContext.assetTrack.formatDescriptions as! [CMAudioFormatDescription]
+        for item in formatDescriptions {
+            guard let fmtDesc = CMAudioFormatDescriptionGetStreamBasicDescription(item) else { return nil }
+            channelCount = Int(fmtDesc.pointee.mChannelsPerFrame)
+            sampleRate = Int32(fmtDesc.pointee.mSampleRate)
+        }
+        
+        reader.timeRange = CMTimeRange(start: CMTime(value: Int64(slice.lowerBound), timescale: sampleRate),
+                                       duration: CMTime(value: Int64(slice.count), timescale: sampleRate))
         let outputSettingsDict: [String : Any] = [
             AVFormatIDKey: Int(kAudioFormatLinearPCM),
             AVLinearPCMBitDepthKey: 16,
@@ -165,13 +174,6 @@ final public class FDWaveformRenderOperation: Operation {
         readerOutput.alwaysCopiesSampleData = false
         reader.add(readerOutput)
 
-        var channelCount = 1
-        let formatDescriptions = audioContext.assetTrack.formatDescriptions as! [CMAudioFormatDescription]
-        for item in formatDescriptions {
-            guard let fmtDesc = CMAudioFormatDescriptionGetStreamBasicDescription(item) else { return nil }
-            channelCount = Int(fmtDesc.pointee.mChannelsPerFrame)
-        }
-        
         var sampleMax = format.type.floorValue
         let samplesPerPixel = max(1, channelCount * slice.count / targetSamples)
         let filter = [Float](repeating: 1.0 / Float(samplesPerPixel), count: samplesPerPixel)