1 -(void)func_encodeFile2 3 {4 5     //NSString *path = [NSHomeDirectory() stringByAppendingFormat:@"/Documents/test.png"];6 7     NSString *filePath = [NSHomeDirectory() stringByAppendingFormat:@"/Documents/iphone4.mov"];8 9
10
11     //文件路径转换为NSData
12
13     NSData *imageDataOrigin = [NSData dataWithContentsOfFile:filePath];
14
15
16
17     // 对前1000位进行异或处理
18
19     unsigned char * cByte = (unsigned char*)[imageDataOrigin bytes];
20
21     for (int index = 0; (index < [imageDataOrigin length]) && (index < 1000); index++, cByte++)
22
23     {
24
25          *cByte = (*cByte) ^ arrayForEncode[index];
26
27     }
28
29     //对NSData进行base64编码
30
31     NSData *imageDataEncode = [GTMBase64 encodeData:imageDataOrigin];
32
33     [imageDataEncode writeToFile:filePath atomically:YES];
34
35 }

 1 -(void)func_decodeFile2 3 {4 5     //NSString *filePath = [NSHomeDirectory() stringByAppendingFormat:@"/Documents/test.png"];6 7     NSString *filePath = [NSHomeDirectory() stringByAppendingFormat:@"/Documents/iphone4.mov"];8 9
10
11     // 读取被加密文件对应的数据
12
13     NSData *dataEncoded = [NSData dataWithContentsOfFile:filePath];
14
15
16
17     // 对NSData进行base64解码
18
19     NSData *dataDecode = [GTMBase64 decodeData:dataEncoded];
20
21
22
23     // 对前1000位进行异或处理
24
25     unsigned char * cByte = (unsigned char*)[dataDecode bytes];
26
27     for (int index = 0; (index < [dataDecode length]) && (index < 10); index++, cByte++)
28
29     {
30
31         *cByte = (*cByte) ^ arrayForEncode[index];
32
33     }
34
35
36
37     [dataDecode writeToFile:filePath atomically:YES];
38 }
39  

 1 [mImageGenerator generateCGImagesAsynchronouslyForTimes:[NSArray arrayWithObject:[NSValue valueWithCMTime:CMTimeMakeWithSeconds(time, NSEC_PER_SEC)]] completionHandler:  2     ^(CMTime requestedTime, CGImageRef image, CMTime actualTime, AVAssetImageGeneratorResult result, NSError *error)  3     {  4            NSLog(@"actual got image at time:%f", CMTimeGetSeconds(actualTime));          if (image)  5         {  6             [CATransaction begin];  7             [CATransaction setDisableActions:YES];  8             [layer setContents:(id)image];  9
10             //UIImage *img = [UIImage imageWithCGImage:image];
11             //UIImageWriteToSavedPhotosAlbum(img, self, nil, nil);
12
13             [CATransaction commit];
14         }
15     }];  

八：iOS开发之流媒体常识

实时流媒体传输必须保证数据包的传输速度大于文件的播放速度，否则用户看到的视频会出现暂停。当网络堵塞情况下视频质量会下降，所以要想保证视频的质量渐进式下载会更好一些。