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我正在制作将主题音乐添加到视频的应用程序。iOS:降低包含iPod音乐的MPMediaItem的比特率
某些用户抱怨说,如果他们的音乐是苹果无损格式,则视频会过大。
我发现这是因为我使用的AVMutableComposition
只是将原始音乐格式放入我生成的视频中。
那么有什么办法可以降低MPMediaItem中的音乐比特率,或者改变它被编码的格式?
这是我用来将音乐添加到视频的代码的代码片段。
AVMutableComposition* mixComposition = [AVMutableComposition composition];
AVMutableCompositionTrack *compositionAudioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio
preferredTrackID:kCMPersistentTrackID_Invalid];
[compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.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];
NSURL *exportUrl = [NSURL fileURLWithPath:_videoOutputPath];
if ([[NSFileManager defaultManager] fileExistsAtPath:_videoOutputPath]){
[[NSFileManager defaultManager] removeItemAtPath:_videoOutputPath error:nil];
}
_assetExport.outputFileType = @"com.apple.quicktime-movie";
_assetExport.outputURL = exportUrl;
_assetExport.shouldOptimizeForNetworkUse = YES;
[_assetExport exportAsynchronouslyWithCompletionHandler:^(void) {}