Ejemplo n.º 1
0
        public void MethodsTest()
        {
            CMTime v, w, x, y;

            v = new CMTime(1, 2);
            w = new CMTime(1, 2);
            x = new CMTime(2, 1);
            y = new CMTime(2, 2);

            // equality operators
            Assert.That(v == w, "Equality #1");
            Assert.That(!(v == x), "Equality #2");
            Assert.That(v != x, "Inequality #1");
            Assert.That(!(v != w), "Inequality #2");
            Assert.That(CMTime.Compare(v, w), Is.EqualTo(0), "Compare #1");
            Assert.That(CMTime.Compare(v, x) != 0, "Compare #2");
            Assert.That(v.Equals(w), "Equals #1");
            Assert.That(!x.Equals(v), "Equals #2");

            // addition operator
            Assert.That(v + w == new CMTime(2, 2), "Addition #1");
            Assert.That(CMTime.Add(v, w) == new CMTime(2, 2), "Addition #2");

            // subtraction operator
            Assert.That(v - w == new CMTime(0, 2), "Subtraction #1");
            Assert.That(CMTime.Subtract(v, w) == new CMTime(0, 2), "Subtraction #2");

            // multiplication operators
            Assert.That(v * 2 == new CMTime(2, 2), "Multiplication * int, #1");
            Assert.That(CMTime.Multiply(v, 3) == new CMTime(3, 2), "Multiplication * int, #2");
            Assert.That(v * 4.0 == new CMTime(4, 2), "Multiplication * double, #1");
            Assert.That(CMTime.Multiply(v, 5.0) == new CMTime(5, 2), "Multiplication * double, #2");

            // ConvertScale
            Assert.That(new CMTime(10, 2).ConvertScale(1, CMTimeRoundingMethod.Default) == new CMTime(5, 1), "ConvertScale #1");

            // FromSeconds
            Assert.That(CMTime.FromSeconds(20, 1) == new CMTime(20, 1), "FromSeconds #1");

            // GetMaximum
            Assert.That(CMTime.GetMaximum(v, y) == y, "GetMaximum #1");

            // GetMinimum
            Assert.That(CMTime.GetMinimum(v, y) == v, "GetMinimum #1");

#if XAMCORE_2_0
            using (var d = x.ToDictionary()) {
                Assert.That(d.RetainCount, Is.EqualTo((nint)1), "RetainCount");
                Assert.That(d.Count, Is.EqualTo((nuint)4), "Count");

                var time = CMTime.FromDictionary(d);
                Assert.That(time, Is.EqualTo(x), "FromDictionary");
            }
#endif
        }
Ejemplo n.º 2
0
        public void CalculateFramerateAtTimestamp(CMTime timeStamp)
        {
            previousSecondTimestamps.Add(timeStamp);

            var oneSecond    = CMTime.FromSeconds(1, 1);
            var oneSecondAgo = CMTime.Subtract(timeStamp, oneSecond);

            while (previousSecondTimestamps.Count > 0 && CMTime.Compare(previousSecondTimestamps[0], oneSecondAgo) < 0)
            {
                previousSecondTimestamps.RemoveAt(0);
            }

            double newRate = Convert.ToDouble(previousSecondTimestamps.Count);

            VideoFrameRate = (VideoFrameRate + newRate) / 2;
        }
Ejemplo n.º 3
0
        private void BuildTransitionComposition(AVMutableComposition composition, AVMutableVideoComposition videoComposition, AVMutableAudioMix audioMix)
        {
            CMTime nextClipStartTime = CMTime.Zero;
            int    clipsCount        = Clips.Count;

            // Make transitionDuration no greater than half the shortest clip duration.
            CMTime transitionDuration = TransitionDuration;

            Console.WriteLine("Clips Count:" + clipsCount);
            Console.WriteLine("Clips Range Count:" + ClipTimeRanges.Count);

            for (int i = 0; i < clipsCount; i++)
            {
                NSValue clipTimeRange = ClipTimeRanges [i];
                if (clipTimeRange != null)
                {
                    CMTime halfClipDuration = clipTimeRange.CMTimeRangeValue.Duration;
                    halfClipDuration.TimeScale *= 2;
                    transitionDuration          = CMTime.GetMinimum(transitionDuration, halfClipDuration);
                }
            }

            // Add two video tracks and two audio tracks.
            var compositionVideoTracks = new AVMutableCompositionTrack [] {
                composition.AddMutableTrack(AVMediaType.Video, 0),
                composition.AddMutableTrack(AVMediaType.Video, 0)
            };
            var compositionAudioTracks = new AVMutableCompositionTrack [] {
                composition.AddMutableTrack(AVMediaType.Audio, 0),
                composition.AddMutableTrack(AVMediaType.Audio, 0)
            };

            var passThroughTimeRanges = new CMTimeRange[clipsCount];
            var transitionTimeRanges  = new CMTimeRange[clipsCount];

            // Place clips into alternating video & audio tracks in composition, overlapped by transitionDuration.
            for (int i = 0; i < clipsCount; i++)
            {
                int         alternatingIndex = i % 2;
                AVAsset     asset            = Clips [i];
                NSValue     clipTimeRange    = ClipTimeRanges [i];
                CMTimeRange timeRangeInAsset;
                if (clipTimeRange != null)
                {
                    timeRangeInAsset = clipTimeRange.CMTimeRangeValue;
                }
                else
                {
                    timeRangeInAsset          = new CMTimeRange();
                    timeRangeInAsset.Start    = CMTime.Zero;
                    timeRangeInAsset.Duration = asset.Duration;
                }
                NSError      error;
                AVAssetTrack clipVideoTrack = asset.TracksWithMediaType(AVMediaType.Video) [0];
                compositionVideoTracks [alternatingIndex].InsertTimeRange(timeRangeInAsset, clipVideoTrack, nextClipStartTime, out error);

                AVAssetTrack clipAudioTrack = asset.TracksWithMediaType(AVMediaType.Audio) [0];
                compositionAudioTracks [alternatingIndex].InsertTimeRange(timeRangeInAsset, clipAudioTrack, nextClipStartTime, out error);

                // Remember the time range in which this clip should pass through.
                // First clip ends with a transition.
                // Second clip begins with a transition.
                // Exclude that transition from the pass through time ranges
                CMTimeRange timeRange = new CMTimeRange();
                timeRange.Start           = nextClipStartTime;
                timeRange.Duration        = timeRangeInAsset.Duration;
                passThroughTimeRanges [i] = timeRange;

                if (i > 0)
                {
                    passThroughTimeRanges[i].Start    = CMTime.Add(passThroughTimeRanges[i].Start, transitionDuration);
                    passThroughTimeRanges[i].Duration = CMTime.Subtract(passThroughTimeRanges[i].Duration, transitionDuration);
                }

                if (i + 1 < clipsCount)
                {
                    passThroughTimeRanges[i].Duration = CMTime.Subtract(passThroughTimeRanges[i].Duration, transitionDuration);
                }

                // The end of this clip will overlap the start of the next by transitionDuration.
                // (Note: this arithmetic falls apart if timeRangeInAsset.duration < 2 * transitionDuration.)
                nextClipStartTime = CMTime.Add(nextClipStartTime, timeRangeInAsset.Duration);
                nextClipStartTime = CMTime.Subtract(nextClipStartTime, transitionDuration);

                // Remember the time range for the transition to the next item
                if (i + 1 < clipsCount)
                {
                    transitionTimeRanges [i] = new CMTimeRange()
                    {
                        Start    = nextClipStartTime,
                        Duration = transitionDuration
                    };
                }
            }

            List <AVVideoCompositionInstruction>    instructions  = new List <AVVideoCompositionInstruction> ();
            List <AVMutableAudioMixInputParameters> trackMixArray = new List <AVMutableAudioMixInputParameters> ();

            // Set up the video composition if we are to perform crossfade transitions between clips.
            for (int i = 0; i < clipsCount; i++)
            {
                int alternatingIndex = i % 2;
                AVMutableVideoCompositionInstruction passThroughInstructions = AVMutableVideoCompositionInstruction.Create() as AVMutableVideoCompositionInstruction;
                passThroughInstructions.TimeRange = passThroughTimeRanges [i];

                AVMutableVideoCompositionLayerInstruction passThroughLayerInstructions = AVMutableVideoCompositionLayerInstruction.FromAssetTrack(compositionVideoTracks [alternatingIndex]);

                passThroughInstructions.LayerInstructions = new AVVideoCompositionLayerInstruction[] { passThroughLayerInstructions };
                instructions.Add(passThroughInstructions);

                if (i + 1 < clipsCount)
                {
                    var transitionInstruction = AVMutableVideoCompositionInstruction.Create() as AVMutableVideoCompositionInstruction;
                    transitionInstruction.TimeRange = transitionTimeRanges [i];
                    var fromLayer = AVMutableVideoCompositionLayerInstruction.FromAssetTrack(compositionVideoTracks [alternatingIndex]);
                    var toLayer   = AVMutableVideoCompositionLayerInstruction.FromAssetTrack(compositionVideoTracks [1 - alternatingIndex]);


                    // Fade in the toLayer by setting a ramp from 0.0 to 1.0.
                    toLayer.SetOpacityRamp(0.0f, 1.0f, transitionTimeRanges [i]);
                    transitionInstruction.LayerInstructions = new AVVideoCompositionLayerInstruction[]
                    {
                        toLayer,
                        fromLayer,
                    };
                    instructions.Add(transitionInstruction);

                    // Add AudioMix to fade in the volume ramps
                    var trackMix = AVMutableAudioMixInputParameters.FromTrack(compositionAudioTracks[0]);
                    trackMix.SetVolumeRamp(1f, 0f, transitionTimeRanges[0]);
                    trackMixArray.Add(trackMix);

                    trackMix = AVMutableAudioMixInputParameters.FromTrack(compositionAudioTracks[1]);
                    trackMix.SetVolumeRamp(0f, 1f, transitionTimeRanges[0]);
                    trackMix.SetVolumeRamp(1f, 1f, passThroughTimeRanges[1]);
                    trackMixArray.Add(trackMix);
                }
            }

            videoComposition.Instructions = instructions.ToArray();
            audioMix.InputParameters      = trackMixArray.ToArray();
        }
        //Utilities methods

        double factorForTimeInRange(CMTime time, CMTimeRange range)
        {
            CMTime elapsed = CMTime.Subtract(time, range.Start);

            return(elapsed.Seconds / range.Duration.Seconds);
        }
Ejemplo n.º 5
0
        void buildTransitionComposition(AVMutableComposition composition, AVMutableVideoComposition videoComposition)
        {
            CMTime nextClipStartTime = CMTime.Zero;
            int    clipsCount        = Clips.Count;

            // Make transitionDuration no greater than half the shortest clip duration.
            CMTime transitionDuration = TransitionDuration;

            foreach (var clipTimeRange in ClipTimeRanges)
            {
                if (clipTimeRange == null)
                {
                    continue;
                }

                CMTime halfClipDuration = clipTimeRange.CMTimeRangeValue.Duration;
                halfClipDuration.TimeScale *= 2;
                transitionDuration          = CMTime.GetMinimum(transitionDuration, halfClipDuration);
            }

            // Add two video tracks and two audio tracks.
            var compositionVideoTracks = new AVMutableCompositionTrack [2];
            var compositionAudioTracks = new AVMutableCompositionTrack [2];

            compositionVideoTracks [0] = composition.AddMutableTrack(AVMediaType.Video, 0);
            compositionVideoTracks [1] = composition.AddMutableTrack(AVMediaType.Video, 0);
            compositionAudioTracks [0] = composition.AddMutableTrack(AVMediaType.Audio, 0);
            compositionAudioTracks [1] = composition.AddMutableTrack(AVMediaType.Audio, 0);

            var passThroughTimeRanges = new CMTimeRange[clipsCount];
            var transitionTimeRanges  = new CMTimeRange[clipsCount];

            // Place clips into alternating video & audio tracks in composition, overlapped by transitionDuration.
            for (int i = 0; i < clipsCount; i++)
            {
                int         alternatingIndex = i % 2;
                AVAsset     asset            = Clips [i];
                NSValue     clipTimeRange    = ClipTimeRanges [i];
                CMTimeRange timeRangeInAsset;
                if (clipTimeRange != null)
                {
                    timeRangeInAsset = clipTimeRange.CMTimeRangeValue;
                }
                else
                {
                    timeRangeInAsset = new CMTimeRange {
                        Start    = CMTime.Zero,
                        Duration = asset.Duration
                    };
                }
                NSError      error          = new NSError();
                AVAssetTrack clipVideoTrack = asset.TracksWithMediaType(AVMediaType.Video) [0];
                compositionVideoTracks [alternatingIndex].InsertTimeRange(timeRangeInAsset, clipVideoTrack, nextClipStartTime, out error);

                AVAssetTrack clipAudioTrack = asset.TracksWithMediaType(AVMediaType.Audio) [0];
                compositionAudioTracks [alternatingIndex].InsertTimeRange(timeRangeInAsset, clipAudioTrack, nextClipStartTime, out error);

                // Remember the time range in which this clip should pass through.
                // First clip ends with a transition.
                // Second clip begins with a transition.
                // Exclude that transition from the pass through time ranges
                passThroughTimeRanges [i] = new CMTimeRange {
                    Start    = nextClipStartTime,
                    Duration = timeRangeInAsset.Duration
                };

                if (i > 0)
                {
                    passThroughTimeRanges[i].Start    = CMTime.Add(passThroughTimeRanges[i].Start, transitionDuration);
                    passThroughTimeRanges[i].Duration = CMTime.Subtract(passThroughTimeRanges[i].Duration, transitionDuration);
                }
                if (i + 1 < clipsCount)
                {
                    passThroughTimeRanges[i].Duration = CMTime.Subtract(passThroughTimeRanges[i].Duration, transitionDuration);
                }

                // The end of this clip will overlap the start of the next by transitionDuration.
                // (Note: this arithmetic falls apart if timeRangeInAsset.duration < 2 * transitionDuration.)
                nextClipStartTime = CMTime.Add(nextClipStartTime, timeRangeInAsset.Duration);
                nextClipStartTime = CMTime.Subtract(nextClipStartTime, transitionDuration);

                // Remember the time range for the transition to the next item.

                if (i + 1 < clipsCount)
                {
                    transitionTimeRanges [i] = new CMTimeRange()
                    {
                        Start    = nextClipStartTime,
                        Duration = transitionDuration
                    };
                }
            }

            // Set up the video composition to perform cross dissolve or diagonal wipe transitions between clips.
            var instructions = new List <AVVideoCompositionInstruction> ();

            // Cycle between "pass through A", "transition from A to B", "pass through B"
            for (int i = 0; i < clipsCount; i++)
            {
                int alternatingIndex = i % 2;

//				if (videoComposition.CustomVideoCompositorClass != null) {
//					var videoInstruction = new CustomVideoCompositionInstruction (compositionVideoTracks [alternatingIndex].TrackID, passThroughTimeRanges [i]);
//					instructions.Add (videoInstruction);
//				} else {
//					// Pass through clip i.
//					var passThroughInstruction = AVMutableVideoCompositionInstruction.Create () as AVMutableVideoCompositionInstruction;
//					passThroughInstruction.TimeRange = passThroughTimeRanges [i];
//					var passThroughLayer = AVMutableVideoCompositionLayerInstruction.FromAssetTrack (compositionVideoTracks [alternatingIndex]);
//					passThroughInstruction.LayerInstructions = new [] { passThroughLayer };
//					instructions.Add (passThroughInstruction);
//
//				}
                //TODO: Remove following call if previous works
                if (videoComposition.CustomVideoCompositorClass.Name != "nil")
                {
                    var videoInstruction = new CustomVideoCompositionInstruction(compositionVideoTracks [alternatingIndex].TrackID, passThroughTimeRanges [i]);
                    instructions.Add(videoInstruction);
                }
                else
                {
                    // Pass through clip i.
                    var passThroughInstruction = AVMutableVideoCompositionInstruction.Create() as AVMutableVideoCompositionInstruction;
                    passThroughInstruction.TimeRange = passThroughTimeRanges [i];
                    var passThroughLayer = AVMutableVideoCompositionLayerInstruction.FromAssetTrack(compositionVideoTracks [alternatingIndex]);
                    passThroughInstruction.LayerInstructions = new [] { passThroughLayer };
                    instructions.Add(passThroughInstruction);
                }

                if (i + 1 < clipsCount)
                {
                    // Add transition from clip i to clip i+1.
//					if (videoComposition.CustomVideoCompositorClass != null) {
//						var videoInstruction = new CustomVideoCompositionInstruction (new NSNumber [] {
//							compositionVideoTracks [0].TrackID,
//							compositionVideoTracks [1].TrackID
//						}, transitionTimeRanges [1]);
//
//						if (alternatingIndex == 0) {
//							videoInstruction.ForegroundTrackID = compositionVideoTracks [alternatingIndex].TrackID;
//							videoInstruction.BackgroundTrackID = compositionVideoTracks [1 - alternatingIndex].TrackID;
//						}
//
//						instructions.Add (videoInstruction);
//					} else {
//						var transitionInstruction = AVMutableVideoCompositionInstruction.Create () as AVMutableVideoCompositionInstruction;
//						transitionInstruction.TimeRange = transitionTimeRanges [i];
//						var fromLayer = AVMutableVideoCompositionLayerInstruction.FromAssetTrack (compositionVideoTracks [alternatingIndex]);
//						var toLayer = AVMutableVideoCompositionLayerInstruction.FromAssetTrack (compositionVideoTracks [1 - alternatingIndex]);
//						transitionInstruction.LayerInstructions = new [] { toLayer, fromLayer };
//						instructions.Add (transitionInstruction);
//					}
                    // TODO: remove following call if previous works
                    if (videoComposition.CustomVideoCompositorClass.Name != "nil")
                    {
                        NSNumber[] sources = new NSNumber[] {
                            new NSNumber(compositionVideoTracks [0].TrackID),
                            new NSNumber(compositionVideoTracks [1].TrackID)
                        };
                        var videoInstructions = new CustomVideoCompositionInstruction(sources, transitionTimeRanges [i]);
                        if (alternatingIndex == 0)
                        {
                            videoInstructions.ForegroundTrackID = compositionVideoTracks [alternatingIndex].TrackID;
                            videoInstructions.BackgroundTrackID = compositionVideoTracks [1 - alternatingIndex].TrackID;
                        }

                        instructions.Add(videoInstructions);
                        Console.WriteLine("Add transition from clip i to clip i+1");
                    }
                    else
                    {
                        AVMutableVideoCompositionInstruction transitionInstruction = AVMutableVideoCompositionInstruction.Create() as AVMutableVideoCompositionInstruction;
                        transitionInstruction.TimeRange = transitionTimeRanges [i];
                        AVMutableVideoCompositionLayerInstruction fromLayer = AVMutableVideoCompositionLayerInstruction.FromAssetTrack(compositionVideoTracks [alternatingIndex]);
                        AVMutableVideoCompositionLayerInstruction toLayer   = AVMutableVideoCompositionLayerInstruction.FromAssetTrack(compositionVideoTracks [1 - alternatingIndex]);
                        transitionInstruction.LayerInstructions = new AVVideoCompositionLayerInstruction[] {
                            fromLayer,
                            toLayer,
                        };
                        instructions.Add(transitionInstruction);
                    }
                }
            }

            videoComposition.Instructions = instructions.ToArray();
        }
Ejemplo n.º 6
0
        private static double FactorForTimeInRange(CMTime time, CMTimeRange range)
        {
            var elapsed = CMTime.Subtract(time, range.Start);

            return(elapsed.Seconds / range.Duration.Seconds);
        }
Ejemplo n.º 7
0
        private void BuildTransitionComposition(AVMutableComposition mutableComposition, AVMutableVideoComposition mutableVideoComposition)
        {
            var nextClipStartTime = CMTime.Zero;
            var clipsCount        = this.Clips.Count;

            // Make transitionDuration no greater than half the shortest clip duration.
            var transitionDuration = this.TransitionDuration;

            foreach (var clipTimeRange in this.ClipTimeRanges)
            {
                var halfClipDuration = clipTimeRange.Duration;
                halfClipDuration.TimeScale *= 2; // You can halve a rational by doubling its denominator.
                transitionDuration          = CMTime.GetMinimum(transitionDuration, halfClipDuration);
            }

            // Add two video tracks and two audio tracks.
            var compositionVideoTracks = new AVMutableCompositionTrack[2];
            var compositionAudioTracks = new AVMutableCompositionTrack[2];

            compositionVideoTracks[0] = mutableComposition.AddMutableTrack(AVMediaType.Video, 0);
            compositionVideoTracks[1] = mutableComposition.AddMutableTrack(AVMediaType.Video, 0);
            compositionAudioTracks[0] = mutableComposition.AddMutableTrack(AVMediaType.Audio, 0);
            compositionAudioTracks[1] = mutableComposition.AddMutableTrack(AVMediaType.Audio, 0);

            var passThroughTimeRanges = new CMTimeRange[clipsCount];
            var transitionTimeRanges  = new CMTimeRange[clipsCount];

            // Place clips into alternating video & audio tracks in composition, overlapped by transitionDuration.
            for (int i = 0; i < clipsCount; i++)
            {
                int alternatingIndex = i % 2; // alternating targets: 0, 1, 0, 1, ...
                var asset            = this.Clips[i];
                var timeRangeInAsset = this.ClipTimeRanges[i];

                var clipVideoTrack = asset.TracksWithMediaType(AVMediaType.Video)[0];
                compositionVideoTracks[alternatingIndex].InsertTimeRange(timeRangeInAsset, clipVideoTrack, nextClipStartTime, out _);

                var clipAudioTrack = asset.TracksWithMediaType(AVMediaType.Audio)[0];
                compositionAudioTracks[alternatingIndex].InsertTimeRange(timeRangeInAsset, clipAudioTrack, nextClipStartTime, out _);

                // Remember the time range in which this clip should pass through.
                // First clip ends with a transition.
                // Second clip begins with a transition.
                // Exclude that transition from the pass through time ranges
                passThroughTimeRanges[i] = new CMTimeRange {
                    Start = nextClipStartTime, Duration = timeRangeInAsset.Duration
                };

                if (i > 0)
                {
                    passThroughTimeRanges[i].Start    = CMTime.Add(passThroughTimeRanges[i].Start, transitionDuration);
                    passThroughTimeRanges[i].Duration = CMTime.Subtract(passThroughTimeRanges[i].Duration, transitionDuration);
                }

                if (i + 1 < clipsCount)
                {
                    passThroughTimeRanges[i].Duration = CMTime.Subtract(passThroughTimeRanges[i].Duration, transitionDuration);
                }

                // The end of this clip will overlap the start of the next by transitionDuration.
                // (Note: this arithmetic falls apart if timeRangeInAsset.duration < 2 * transitionDuration.)
                nextClipStartTime = CMTime.Add(nextClipStartTime, timeRangeInAsset.Duration);
                nextClipStartTime = CMTime.Subtract(nextClipStartTime, transitionDuration);

                // Remember the time range for the transition to the next item.
                if (i + 1 < clipsCount)
                {
                    transitionTimeRanges[i] = new CMTimeRange {
                        Start = nextClipStartTime, Duration = transitionDuration
                    };
                }
            }

            // Set up the video composition to perform cross dissolve or diagonal wipe transitions between clips.
            var instructions = new List <AVVideoCompositionInstruction>();

            // Cycle between "pass through A", "transition from A to B", "pass through B"
            for (int i = 0; i < clipsCount; i++)
            {
                int alternatingIndex = i % 2; // alternating targets

                if (mutableVideoComposition.CustomVideoCompositorClass != null)
                {
                    var videoInstruction = new CustomVideoCompositionInstruction(compositionVideoTracks[alternatingIndex].TrackID, passThroughTimeRanges[i]);
                    instructions.Add(videoInstruction);
                }
                else
                {
                    // Pass through clip i.
                    var passThroughInstruction = AVMutableVideoCompositionInstruction.Create() as AVMutableVideoCompositionInstruction;
                    passThroughInstruction.TimeRange = passThroughTimeRanges[i];

                    var passThroughLayer = AVMutableVideoCompositionLayerInstruction.FromAssetTrack(compositionVideoTracks[alternatingIndex]);
                    passThroughInstruction.LayerInstructions = new[] { passThroughLayer };

                    instructions.Add(passThroughInstruction);
                }

                if (i + 1 < clipsCount)
                {
                    // Add transition from clip i to clip i+1.
                    if (mutableVideoComposition.CustomVideoCompositorClass != null)
                    {
                        var videoInstruction = new CustomVideoCompositionInstruction(new NSNumber[]
                        {
                            compositionVideoTracks[0].TrackID,
                            compositionVideoTracks[1].TrackID
                        }, transitionTimeRanges[i]);

                        if (alternatingIndex == 0)
                        {
                            // First track -> Foreground track while compositing
                            videoInstruction.ForegroundTrackId = compositionVideoTracks[alternatingIndex].TrackID;
                            // Second track -> Background track while compositing
                            videoInstruction.BackgroundTrackId = compositionVideoTracks[1 - alternatingIndex].TrackID;
                        }

                        instructions.Add(videoInstruction);
                    }
                    else
                    {
                        var transitionInstruction = AVMutableVideoCompositionInstruction.Create() as AVMutableVideoCompositionInstruction;
                        transitionInstruction.TimeRange = transitionTimeRanges[i];

                        var fromLayer = AVMutableVideoCompositionLayerInstruction.FromAssetTrack(compositionVideoTracks[alternatingIndex]);
                        var toLayer   = AVMutableVideoCompositionLayerInstruction.FromAssetTrack(compositionVideoTracks[1 - alternatingIndex]);

                        transitionInstruction.LayerInstructions = new[] { toLayer, fromLayer };
                        instructions.Add(transitionInstruction);
                    }
                }
            }

            mutableVideoComposition.Instructions = instructions.ToArray();
        }
        public Task <OperationResult> AddAudioToVideoTrack(string videoFilePath, string audioFilePath, string outputFilePath,
                                                           float volume = 1, float fadeOutDuration = 0)
        {
            var tcs = new TaskCompletionSource <OperationResult>();

            var composition           = AVMutableComposition.Create();
            var videoCompositionTrack = composition.AddMutableTrack(AVMediaType.Video, 0);
            var audioCompositionTrack = composition.AddMutableTrack(AVMediaType.Audio, 0);

            var videoUrl        = NSUrl.FromFilename(videoFilePath);
            var videoAsset      = AVAsset.FromUrl(videoUrl);
            var videoAssetTrack = videoAsset.TracksWithMediaType(AVMediaType.Video).First();

            var audioUrl        = NSUrl.FromFilename(audioFilePath);
            var audioAsset      = AVAsset.FromUrl(audioUrl);
            var audioAssetTrack = audioAsset.TracksWithMediaType(AVMediaType.Audio).First();

            CGSize size = videoAssetTrack.NaturalSize;
            CMTime time = CMTime.Zero;

            var range = new CMTimeRange
            {
                Start    = CMTime.Zero,
                Duration = videoAssetTrack.TimeRange.Duration
            };

            NSError error = null;

            videoCompositionTrack.InsertTimeRange(range, videoAssetTrack, time, out error);
            if (error != null)
            {
                Console.WriteLine("Error adding video composition track: " + error.LocalizedDescription);
            }

            error = null;
            audioCompositionTrack.InsertTimeRange(range, audioAssetTrack, time, out error);
            if (error != null)
            {
                Console.WriteLine("Error adding audio composition track: " + error.LocalizedDescription);
            }


            var audioMix         = AVMutableAudioMix.Create();
            var audioInputParams = AVMutableAudioMixInputParameters.FromTrack(audioCompositionTrack);

            audioInputParams.SetVolume(volume, CMTime.Zero);

            if (fadeOutDuration > 0)
            {
                var fadeOutStartTime = CMTime.Subtract(videoAssetTrack.TimeRange.Duration, CMTime.FromSeconds(fadeOutDuration, audioAssetTrack.NaturalTimeScale));
                var fadeOutRange     = new CMTimeRange
                {
                    Start    = fadeOutStartTime,
                    Duration = CMTime.FromSeconds(fadeOutDuration, audioAssetTrack.NaturalTimeScale)
                };

                audioInputParams.SetVolumeRamp(volume, 0.0f, fadeOutRange);
            }

            audioMix.InputParameters = new[] { audioInputParams };

            var session = new AVAssetExportSession(composition, AVAssetExportSession.PresetHighestQuality);

            session.OutputUrl      = NSUrl.FromFilename(outputFilePath);
            session.OutputFileType = AVFileType.Mpeg4;
            session.AudioMix       = audioMix;

            session.ExportAsynchronously(() =>
            {
                if (session.Status == AVAssetExportSessionStatus.Failed)
                {
                    tcs.SetResult(OperationResult.AsFailure(session.Error.LocalizedDescription));
                }
                else
                {
                    tcs.SetResult(OperationResult.AsSuccess());
                }
            });

            return(tcs.Task);
        }