AVSimpleEditor/AVSEAddMusicCommand.m
/* |
File: AVSEAddMusicCommand.m |
Abstract: A subclass of AVSECommand which uses AVMutableAudioMix. This tool replaces the existing audio track of a AVMutableComposition with a custom audio track and shows the use of AVMutableAudioMixInputParameters to add volume ramps to the audio track. |
Version: 1.1 |
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*/ |
#import "AVSEAddMusicCommand.h" |
@implementation AVSEAddMusicCommand |
- (void)performWithAsset:(AVAsset*)asset |
{ |
AVAssetTrack *assetVideoTrack = nil; |
AVAssetTrack *assetAudioTrack = nil; |
// Check if the asset contains video and audio tracks |
if ([[asset tracksWithMediaType:AVMediaTypeVideo] count] != 0) { |
assetVideoTrack = [asset tracksWithMediaType:AVMediaTypeVideo][0]; |
} |
if ([[asset tracksWithMediaType:AVMediaTypeAudio] count] != 0) { |
assetAudioTrack = [asset tracksWithMediaType:AVMediaTypeAudio][0]; |
} |
NSError *error = nil; |
// Step 1 |
// Extract the custom audio track to be added to the composition |
NSString *audioURL = [[NSBundle mainBundle] pathForResource:@"Music" ofType:@"m4a"]; |
AVAsset *audioAsset = [[AVURLAsset alloc] initWithURL:[NSURL fileURLWithPath:audioURL] options:nil]; |
AVAssetTrack *newAudioTrack = [audioAsset tracksWithMediaType:AVMediaTypeAudio][0]; |
// Step 2 |
// Create a composition with the given asset and insert audio and video tracks into it from the asset |
if (!self.mutableComposition) { |
// Check whether a composition has already been created, i.e, some other tool has already been applied. |
// Create a new composition |
self.mutableComposition = [AVMutableComposition composition]; |
// Add tracks to composition from the input video asset |
if (assetVideoTrack != nil) { |
AVMutableCompositionTrack *compositionVideoTrack = [self.mutableComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid]; |
[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, [asset duration]) ofTrack:assetVideoTrack atTime:kCMTimeZero error:&error]; |
} |
if (assetAudioTrack != nil) { |
AVMutableCompositionTrack *compositionAudioTrack = [self.mutableComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid]; |
[compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, [asset duration]) ofTrack:assetAudioTrack atTime:kCMTimeZero error:&error]; |
} |
} |
// Step 3 |
// Add custom audio track to the composition |
AVMutableCompositionTrack *customAudioTrack = [self.mutableComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid]; |
[customAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, [self.mutableComposition duration]) ofTrack:newAudioTrack atTime:kCMTimeZero error:&error]; |
// Step 4 |
// Mix parameters sets a volume ramp for the audio track to be mixed with existing audio track for the duration of the composition |
AVMutableAudioMixInputParameters *mixParameters = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:customAudioTrack]; |
[mixParameters setVolumeRampFromStartVolume:1 toEndVolume:0 timeRange:CMTimeRangeMake(kCMTimeZero, self.mutableComposition.duration)]; |
self.mutableAudioMix = [AVMutableAudioMix audioMix]; |
self.mutableAudioMix.inputParameters = @[mixParameters]; |
// Step 5 |
// Notify AVSEViewController about add music operation completion |
[[NSNotificationCenter defaultCenter] postNotificationName:AVSEEditCommandCompletionNotification object:self]; |
} |
@end |
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