音频视频与主视频声音合并

Question

我可以很好地将视频与另一个音频合并。但我还需要最终输出视频中的主视频声音。这意味着我想用低音量设置主视频声音。我该怎么做？

 -(void)mergeAndSave
{
//Create AVMutableComposition Object which will hold our multiple AVMutableCompositionTrack or we can say it will hold our video and audio files.
AVMutableComposition* mixComposition = [AVMutableComposition composition];
//Now first load your audio file using AVURLAsset. Make sure you give the correct path of your videos.
NSURL *audio_url = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"Asteroid_Sound" ofType:@"mp3"]];
AVURLAsset  *audioAsset = [[AVURLAsset alloc]initWithURL:audio_url options:nil];
CMTimeRange audio_timeRange = CMTimeRangeMake(kCMTimeZero, audioAsset.duration);
//Now we are creating the first AVMutableCompositionTrack containing our audio and add it to our AVMutableComposition object.
AVMutableCompositionTrack *b_compositionAudioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
[b_compositionAudioTrack insertTimeRange:audio_timeRange ofTrack:[[audioAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:kCMTimeZero error:nil];
//Now we will load video file.
NSURL *video_url = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"Asteroid_Video" ofType:@"m4v"]];
AVURLAsset  *videoAsset = [[AVURLAsset alloc]initWithURL:video_url options:nil];
CMTimeRange video_timeRange = CMTimeRangeMake(kCMTimeZero,audioAsset.duration);
//Now we are creating the second AVMutableCompositionTrack containing our video and add it to our AVMutableComposition object.
AVMutableCompositionTrack *a_compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
[a_compositionVideoTrack insertTimeRange:video_timeRange ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:kCMTimeZero error:nil];
//decide the path where you want to store the final video created with audio and video merge.
NSArray *dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *docsDir = [dirPaths objectAtIndex:0];
NSString *outputFilePath = [docsDir stringByAppendingPathComponent:[NSString stringWithFormat:@"FinalVideo.mov"]];
NSURL *outputFileUrl = [NSURL fileURLWithPath:outputFilePath];
if ([[NSFileManager defaultManager] fileExistsAtPath:outputFilePath])
    [[NSFileManager defaultManager] removeItemAtPath:outputFilePath error:nil];
//Now create an AVAssetExportSession object that will save your final video at specified path.
AVAssetExportSession* _assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetHighestQuality];
_assetExport.outputFileType = @"com.apple.quicktime-movie";
_assetExport.outputURL = outputFileUrl;
[_assetExport exportAsynchronouslyWithCompletionHandler:
 ^(void ) {
     dispatch_async(dispatch_get_main_queue(), ^{
         [self exportDidFinish:_assetExport];
     });
 }
 ];
}

这是我如何将视频与音频合并的代码。

Answer 1

您可以在一个作品中有多个音轨，您可以创建另一个具有主视频音频的音轨：

AVMutableCompositionTrack *mainVideoAudioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
[mainVideoAudioTrack insertTimeRange:video_timeRange ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:kCMTimeZero error:nil];

为了减少您需要创建的音量，请使用AVAudioMix：

AVMutableAudioMix *audioMix = [AVMutableAudioMix audioMix];
//Instruction for main video audio track
AVMutableAudioMixInputParameters *mainAudioMixParams = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:mainVideoAudioTrack];
[mainAudioMixParams setVolume:0.25 atTime:kCMTimeZero];
//Instruction for background audio track
AVMutableAudioMixInputParameters *b_audioMixParams = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:b_compositionAudioTrack];
[b_audioMixParams setVolume:1 atTime:kCMTimeZero];
audioMix.inputParameters = @[b_audioMixParams, mainAudioMixParams];

然后，当您导出时，您需要将音频混音添加到导出会话中，如下所示：

_assetExport.audioMix = audioMix;