如何在iphone SDK上添加音频到视频文件

Question

我有一个视频文件和一个音频文件.是否可以将其与声音文件合并为一个视频.我认为AVMutableComposition应该对我有所帮助,但我仍然不明白如何.任何建议？

Answer 1

谢谢Daniel.我想通了,很简单.

AVURLAsset* audioAsset = [[AVURLAsset alloc]initWithURL:audioUrl options:nil];
AVURLAsset* videoAsset = [[AVURLAsset alloc]initWithURL:videoUrl options:nil];

AVMutableComposition* mixComposition = [AVMutableComposition composition];

AVMutableCompositionTrack *compositionCommentaryTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio 
                                                                                    preferredTrackID:kCMPersistentTrackID_Invalid];
[compositionCommentaryTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, audioAsset.duration) 
                                    ofTrack:[[audioAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] 
                                     atTime:kCMTimeZero error:nil];

AVMutableCompositionTrack *compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo 
                                                                                    preferredTrackID:kCMPersistentTrackID_Invalid];
[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration) 
                               ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] 
                                atTime:kCMTimeZero error:nil];

AVAssetExportSession* _assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition 
                                                                      presetName:AVAssetExportPresetPassthrough];   

NSString* videoName = @"export.mov";

NSString *exportPath = [NSTemporaryDirectory() stringByAppendingPathComponent:videoName];
NSURL    *exportUrl = [NSURL fileURLWithPath:exportPath];

if ([[NSFileManager defaultManager] fileExistsAtPath:exportPath]) 
{
    [[NSFileManager defaultManager] removeItemAtPath:exportPath error:nil];
}

_assetExport.outputFileType = @"com.apple.quicktime-movie";
DLog(@"file type %@",_assetExport.outputFileType);
_assetExport.outputURL = exportUrl;
_assetExport.shouldOptimizeForNetworkUse = YES;

[_assetExport exportAsynchronouslyWithCompletionHandler:
 ^(void ) {      
            // your completion code here
     }       
 }
 ];

Answer 2

是的,这是可能的,这里是用于向现有组合添加音频的代码片段,我从苹果示例代码中抓取这个,你应该查看整个项目,你会发现它非常有用,项目是AVEditDemo而你可以在他们发布的WWDC 2010资料中找到它developer.apple.com/videos/wwdc/2010.希望有所帮助

 - (void)addCommentaryTrackToComposition:(AVMutableComposition *)composition withAudioMix:(AVMutableAudioMix *)audioMix

{

NSInteger i;

NSArray *tracksToDuck = [composition tracksWithMediaType:AVMediaTypeAudio]; // before we add the commentary



// Clip commentary duration to composition duration.

CMTimeRange commentaryTimeRange = CMTimeRangeMake(self.commentaryStartTime, self.commentary.duration);

if (CMTIME_COMPARE_INLINE(CMTimeRangeGetEnd(commentaryTimeRange), >, [composition duration]))

    commentaryTimeRange.duration = CMTimeSubtract([composition duration], commentaryTimeRange.start);



// Add the commentary track.

AVMutableCompositionTrack *compositionCommentaryTrack = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];

[compositionCommentaryTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, commentaryTimeRange.duration) ofTrack:[[self.commentary tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:commentaryTimeRange.start error:nil];





NSMutableArray *trackMixArray = [NSMutableArray array];

CMTime rampDuration = CMTimeMake(1, 2); // half-second ramps

for (i = 0; i < [tracksToDuck count]; i++) {

    AVMutableAudioMixInputParameters *trackMix = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:[tracksToDuck objectAtIndex:i]];

    [trackMix setVolumeRampFromStartVolume:1.0 toEndVolume:0.2 timeRange:CMTimeRangeMake(CMTimeSubtract(commentaryTimeRange.start, rampDuration), rampDuration)];

    [trackMix setVolumeRampFromStartVolume:0.2 toEndVolume:1.0 timeRange:CMTimeRangeMake(CMTimeRangeGetEnd(commentaryTimeRange), rampDuration)];

    [trackMixArray addObject:trackMix];

}

audioMix.inputParameters = trackMixArray;

}