如何在iPhone SDK中合並音頻和視頻

Question

我正在創建一個項目，在其中我使用目標c中的以下代碼合並視頻和音頻。

AVMutableComposition* mixComposition = [AVMutableComposition composition];
NSString *audio_inputFilePath = [libraryDirectory stringByAppendingPathComponent:@"SelectedSong.wav"];
NSURL    *audio_inputFileUrl = [NSURL fileURLWithPath:audio_inputFilePath];
AVURLAsset* audioAsset = [[AVURLAsset alloc]initWithURL:audio_inputFileUrl options:nil];

NSString *videoOutputPath = [libraryDirectory stringByAppendingPathComponent:@"Video.mp4"];
NSURL    *video_inputFileUrl = [NSURL fileURLWithPath:videoOutputPath];
AVURLAsset* videoAsset = [[AVURLAsset alloc]initWithURL:video_inputFileUrl options:nil];

CMTimeRange video_timeRange = CMTimeRangeMake(kCMTimeZero,videoAsset.duration);

AVMutableCompositionTrack *a_compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];

[a_compositionVideoTrack insertTimeRange:video_timeRange ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:kCMTimeZero error:nil];

AVMutableCompositionTrack *b_compositionAudioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];

[b_compositionAudioTrack insertTimeRange:audio_timeRange ofTrack:[[audioAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:kCMTimeZero error:nil];

AVAssetExportSession* _assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetHighestQuality];
_assetExport.outputFileType = @"com.apple.quicktime-movie";
//_assetExport.outputFileType = AVFileTypeMPEG4 ;
//NSLog(@"support file types= %@", [_assetExport supportedFileTypes]);
_assetExport.outputURL = outputFileUrl;

[_assetExport exportAsynchronouslyWithCompletionHandler:^{
        };

---

但

 [[audioAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0]

它返回設備中的空數組。 當在模擬器中檢查它可以正常工作。

---

所以請幫助我如何解決它。

Answer 1

在這種情況下

[[audioAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0]

[b_compositionAudioTrack insertTimeRange:audio_timeRange ofTrack:[[audioAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:nextClipStartTime error:nil]; 這無法讀取數組。

因為特定文件中沒有聲音/音頻。僅在那些情況下，當垂直多媒體文件中沒有聲音/音頻時，才會出現此錯誤。