在iOS中，摄像头录制的视频是mov格式的，虽然mov兼容mp4，但是有些需求需要用到mp4格式的视频文件。

AVURLAsset *avAsset = [AVURLAsset URLAssetWithURL:[NSURL fileURLWithPath:path] options:nil]; NSArray *compatiblePresets = [AVAssetExportSession exportPresetsCompatibleWithAsset:avAsset]; if ([compatiblePresets containsObject:AVAssetExportPresetLowQuality]) { AVAssetExportSession *exportSession = [[AVAssetExportSession alloc]initWithAsset:avAsset presetName:AVAssetExportPresetPassthrough]; NSString *exportPath = [NSString stringWithFormat:@"%@/%@.mp4", [NSHomeDirectory() stringByAppendingString:@"/tmp"], @"1"]; exportSession.outputURL = [NSURL fileURLWithPath:exportPath]; NSLog(@"%@", exportPath); exportSession.outputFileType = AVFileTypeMPEG4; [exportSession exportAsynchronouslyWithCompletionHandler:^{ switch ([exportSession status]) { case AVAssetExportSessionStatusFailed: NSLog(@"Export failed: %@", [[exportSession error] localizedDescription]); break; case AVAssetExportSessionStatusCancelled: NSLog(@"Export canceled"); break; case AVAssetExportSessionStatusCompleted: NSLog(@"转换成功"); break; default: break; } }]; }