iOS 开发中 通过AVAssetWriter将录像视频写到指定文件

 

分类： iphone 2012-10-07 16:37  583人阅读  评论(0)  收藏  举报

iphone 图像处理 string 算法 工作

转自：http://flhs-wdw.blog.sohu.com/207300574.html

 iphone提供了AVFoundation库来方便的操作多媒体设备，AVAssetWriter这个类可以方便的将图像和音频写成一个完整的视频文件。甚至将整个应用的操作录制下来，也不是什么困难的事情。

      这里先说一下如何将录像的视频写到指定文件中去：

      首先先准备好AVCaptureSession，当录制开始后，可以控制调用相关回调来取音视频的每一贞数据。

[cpp]  view plain copy

1.     NSError * error;  
2.   
3.     session = [[AVCaptureSession alloc] init];  
4.   
5.     [session beginConfiguration];  
6.   
7.     [session setSessionPreset:AVCaptureSessionPreset640x480];  
8.   
9.     [self initVideoAudioWriter];  
10.   
11.     AVCaptureDevice * videoDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];  
12.   
13.     AVCaptureDeviceInput *videoInput = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:&error];  
14.   
15.       
16.   
17.     AVCaptureDevice * audioDevice1 = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];  
18.   
19.     AVCaptureDeviceInput *audioInput1 = [AVCaptureDeviceInput deviceInputWithDevice:audioDevice1 error:&error];  
20.   
21.     videoOutput = [[AVCaptureVideoDataOutput alloc] init];  
22.   
23.     [videoOutput setAlwaysDiscardsLateVideoFrames:YES];   
24.   
25.     [videoOutput setVideoSettings:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA]forKey:(id)kCVPixelBufferPixelFormatTypeKey]];   
26.   
27.     [videoOutput setSampleBufferDelegate:self queue:dispatch_get_main_queue()];  
28.   
29.   
30.   
31.     audioOutput = [[AVCaptureAudioDataOutput alloc] init];  
32.   
33. numberWithInt:kCVPixelFormatType_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey]];   
34.   
35.     [audioOutput setSampleBufferDelegate:self queue:dispatch_get_main_queue()];  
36.   
37.     [session addInput:videoInput];  
38.   
39.     [session addInput:audioInput1];  
40.   
41.     [session addOutput:videoOutput];  
42.   
43.     [session addOutput:audioOutput];  
44.   
45.       
46.   
47.     [session commitConfiguration];  
48.   
49.     [session startRunning];  

回调函数：

[cpp]  view plain copy

1. -(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {  
2.   
3.       
4.   
5.     //CVPixelBufferRef pixelBuffer = (CVPixelBufferRef)CMSampleBufferGetImageBuffer(sampleBuffer);  
6.   
7.       
8.   
9.     NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];   
10.   
11.   
12.   
13.     static int frame = 0;  
14.   
15.     CMTime lastSampleTime = CMSampleBufferGetPresentationTimeStamp(sampleBuffer);  
16.   
17.     if( frame == 0 && videoWriter.status != AVAssetWriterStatusWriting  )  
18.   
19.     {  
20.   
21.         [videoWriter startWriting];  
22.   
23.         [videoWriter startSessionAtSourceTime:lastSampleTime];  
24.   
25.     }  
26.   
27.     if (captureOutput == videoOutput)  
28.   
29.     {  
30.   
31.               
32.   
33. /           if( videoWriter.status > AVAssetWriterStatusWriting )  
34.   
35.            {  
36.   
37.                 NSLog(@"Warning: writer status is %d", videoWriter.status);  
38.   
39.                 if( videoWriter.status == AVAssetWriterStatusFailed )  
40.   
41.                     NSLog(@"Error: %@", videoWriter.error);  
42.   
43.                 return;  
44.   
45.             }  
46.   
47.             if ([videoWriterInput isReadyForMoreMediaData])  
48.   
49.                 if( ![videoWriterInput appendSampleBuffer:sampleBuffer] )  
50.   
51.                     NSLog(@"Unable to write to video input");  
52.   
53.                 else  
54.   
55.                     NSLog(@"already write vidio");  
56.   
57.         }  
58.   
59.     }  
60.   
61.     else if (captureOutput == audioOutput)  
62.   
63.     {  
64.   
65.         if( videoWriter.status > AVAssetWriterStatusWriting )  
66.   
67.         {  
68.   
69.             NSLog(@"Warning: writer status is %d", videoWriter.status);  
70.   
71.             if( videoWriter.status == AVAssetWriterStatusFailed )  
72.   
73.                 NSLog(@"Error: %@", videoWriter.error);  
74.   
75.             return;  
76.   
77.         }  
78.   
79.         if ([audioWriterInput isReadyForMoreMediaData])  
80.   
81.             if( ![audioWriterInput appendSampleBuffer:sampleBuffer] )  
82.   
83.                 NSLog(@"Unable to write to audio input");  
84.   
85.             else  
86.   
87.                 NSLog(@"already write audio");  
88.   
89.     }  
90.   
91.     if (frame == FrameCount)  
92.   
93.     {  
94.   
95.         [self closeVideoWriter];  
96.   
97.     }  
98.   
99.     frame ++;  
100.   
101.     [pool drain];   
102.   
103. }  

剩下的工作就是初始化AVAssetWriter，包括音频与视频输入输出：

[cpp]  view plain copy

1. -(void) initVideoAudioWriter  
2.   
3. {  
4.   
5.     CGSize size = CGSizeMake(480, 320);  
6.   
7.       
8.   
9.       
10.   
11.     NSString *betaCompressionDirectory = [NSHomeDirectory()stringByAppendingPathComponent:@"Documents/Movie.mp4"];  
12.   
13.       
14.   
15.     NSError *error = nil;  
16.   
17.       
18.   
19.     unlink([betaCompressionDirectory UTF8String]);  
20.   
21.       
22.   
23.     //----initialize compression engine  
24.   
25.     self.videoWriter = [[AVAssetWriter alloc] initWithURL:[NSURLfileURLWithPath:betaCompressionDirectory]  
26.   
27.                                                  fileType:AVFileTypeQuickTimeMovie  
28.   
29.                                                     error:&error];  
30.   
31.     NSParameterAssert(videoWriter);  
32.   
33.     if(error)  
34.   
35.         NSLog(@"error = %@", [error localizedDescription]);  
36.   
37.     NSDictionary *videoCompressionProps = [NSDictionary dictionaryWithObjectsAndKeys:  
38.   
39.                                            [NSNumber numberWithDouble:128.0*1024.0],AVVideoAverageBitRateKey,  
40.   
41.                                            nil ];  
42.   
43.       
44.   
45.     NSDictionary *videoSettings = [NSDictionarydictionaryWithObjectsAndKeys:AVVideoCodecH264, AVVideoCodecKey,  
46.   
47.                                    [NSNumber numberWithInt:size.width], AVVideoWidthKey,  
48.   
49.                                    [NSNumber numberWithInt:size.height],AVVideoHeightKey,videoCompressionProps, AVVideoCompressionPropertiesKey, nil];  
50.   
51.     self.videoWriterInput = [AVAssetWriterInputassetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:videoSettings];  
52.   
53.       
54.   
55.     NSParameterAssert(videoWriterInput);  
56.   
57.       
58.   
59.     videoWriterInput.expectsMediaDataInRealTime = YES;  
60.   
61.       
62.   
63.     NSDictionary *sourcePixelBufferAttributesDictionary = [NSDictionarydictionaryWithObjectsAndKeys:  
64.   
65.                                                            [NSNumbernumberWithInt:kCVPixelFormatType_32ARGB], kCVPixelBufferPixelFormatTypeKey, nil];  
66.   
67.       
68.   
69.     self.adaptor = [AVAssetWriterInputPixelBufferAdaptorassetWriterInputPixelBufferAdaptorWithAssetWriterInput:videoWriterInput  
70.   
71.                                                                                    sourcePixelBufferAttributes:sourcePixelBufferAttributesDictionary];  
72.   
73.     NSParameterAssert(videoWriterInput);  
74.   
75.     NSParameterAssert([videoWriter canAddInput:videoWriterInput]);  
76.   
77.       
78.   
79.     if ([videoWriter canAddInput:videoWriterInput])  
80.   
81.         NSLog(@"I can add this input");  
82.   
83.     else  
84.   
85.         NSLog(@"i can't add this input");  
86.   
87.   
88.   
89.     // Add the audio input  
90.   
91.     AudioChannelLayout acl;  
92.   
93.     bzero( &acl, sizeof(acl));  
94.   
95.     acl.mChannelLayoutTag = kAudioChannelLayoutTag_Mono;  
96.   
97.   
98.   
99.     NSDictionary* audioOutputSettings = nil;    
100.   
101. //    audioOutputSettings = [ NSDictionary dictionaryWithObjectsAndKeys:                         
102.   
103. //                           [ NSNumber numberWithInt: kAudioFormatAppleLossless ], AVFormatIDKey,  
104.   
105. //                           [ NSNumber numberWithInt: 16 ], AVEncoderBitDepthHintKey,  
106.   
107. //                           [ NSNumber numberWithFloat: 44100.0 ], AVSampleRateKey,  
108.   
109. //                           [ NSNumber numberWithInt: 1 ], AVNumberOfChannelsKey,                                        
110.   
111. //                           [ NSData dataWithBytes: &acl length: sizeof( acl ) ], AVChannelLayoutKey,  
112.   
113. //                           nil ];  
114.   
115.     audioOutputSettings = [ NSDictionary dictionaryWithObjectsAndKeys:                         
116.   
117.                            [ NSNumber numberWithInt: kAudioFormatMPEG4AAC ], AVFormatIDKey,  
118.   
119.                            [ NSNumber numberWithInt:64000], AVEncoderBitRateKey,  
120.   
121.                            [ NSNumber numberWithFloat: 44100.0 ], AVSampleRateKey,  
122.   
123.                            [ NSNumber numberWithInt: 1 ], AVNumberOfChannelsKey,                                        
124.   
125.                            [ NSData dataWithBytes: &acl length: sizeof( acl ) ], AVChannelLayoutKey,  
126.   
127.                            nil ];  
128.   
129.   
130.   
131.     audioWriterInput = [[AVAssetWriterInput   
132.   
133.                       assetWriterInputWithMediaType: AVMediaTypeAudio   
134.   
135.                       outputSettings: audioOutputSettings ] retain];  
136.   
137.   
138.   
139.     audioWriterInput.expectsMediaDataInRealTime = YES;  
140.   
141.     // add input  
142.   
143.     [videoWriter addInput:audioWriterInput];  
144.   
145.     [videoWriter addInput:videoWriterInput];  
146.   
147. }