需求

公司混合開發(fā)但汞，uni端拍小視頻不是很理想，為達(dá)到仿微信效果凛辣，原生插件走起

思路

第1步：1個(gè)AVCaptureSession, 1塊AVCaptureVideoPreviewLayer[考慮兼容替換成AVPreView]

第2步：視頻錄制需video & audio, 需要對(duì)應(yīng)的AVCaptureDeviceInput，同理對(duì)應(yīng)的AVCaptureVideoDataOutput與AVCaptureAudioDataOutput

第3步：代理中設(shè)置output區(qū)分video與audio, 并將對(duì)應(yīng)的CMSampleBufferRef寫入到視頻文件中

第4步：寫入視頻文件中，用到AVAssetWriter, 對(duì)應(yīng)video & audio 需兩個(gè)AVAssetWriterInput, 加入AVAssetWriter

第5步：CMSampleBufferRef不斷過來框弛，AssetWriter不斷寫入，直到停止

上菜

第一步的初始化就不寫了捕捂，沒事可以翻看本人前面的博客

第2步：兩個(gè)AVCaptureDeviceInput 兩個(gè)Output, 且設(shè)置Output的代理

self.videoInput = [[AVCaptureDeviceInput alloc] initWithDevice:device error:&error];
if (error) {
    NSLog(@"取得設(shè)備攝入videoInput對(duì)象時(shí)出錯(cuò), 錯(cuò)誤原因: %@", error);
    return;
}

// 設(shè)備添加到會(huì)話中
if ([self.session canAddInput:self.videoInput]) {
    [self.session addInput:self.videoInput];
}

[self.videoOutput setSampleBufferDelegate:self queue:self.videoQueue];
if ([self.session canAddOutput:self.videoOutput]) {
    [self.session addOutput:self.videoOutput];
}

// 音頻相關(guān)
AVCaptureDevice *adevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
self.audioInput = [[AVCaptureDeviceInput alloc] initWithDevice:adevice error:&error];

if ([self.session canAddInput:self.audioInput]) {
    [self.session addInput:self.audioInput];
}

[self.audioOutput setSampleBufferDelegate:self queue:self.videoQueue];
if ([self.session canAddOutput:self.audioOutput]) {
    [self.session addOutput:self.audioOutput];
}

// 視頻輸出
- (AVCaptureVideoDataOutput *)videoOutput {
    if (!_videoOutput) {
        _videoOutput = [[AVCaptureVideoDataOutput alloc] init];
        _videoOutput.alwaysDiscardsLateVideoFrames = YES;
    }
    return _videoOutput;
}

// 音頻輸出
- (AVCaptureAudioDataOutput *)audioOutput {
    if (!_audioOutput) {
        _audioOutput = [[AVCaptureAudioDataOutput alloc] init];
    }
    return _audioOutput;
}

第3步：?jiǎn)?dòng)Session功咒，代理里面操作CMSampleBufferRef

#pragma mark - AVCaptureVideoDataOutputSampleBufferDelegate & AVCaptureAudioDataOutputSampleBufferDelegate
- (void)captureOutput:(AVCaptureOutput *)output didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
    @autoreleasepool {
        // 視頻
        if (connection == [self.videoOutput connectionWithMediaType:AVMediaTypeVideo]) {
            if (!self.manager.outputVideoFormatDescription) {
                @synchronized(self) {
                    CMFormatDescriptionRef formatDescription = CMSampleBufferGetFormatDescription(sampleBuffer);
                    self.manager.outputVideoFormatDescription = formatDescription;
                }
            } else {
                @synchronized(self) {
                    if (self.manager.state == StateRecording) {
                        [self.manager appendBuffer:sampleBuffer type:AVMediaTypeVideo];
                    }
                }
            }
        }
        
        //音頻
        if (connection == [self.audioOutput connectionWithMediaType:AVMediaTypeAudio]) {
            if (!self.manager.outputAudioFormatDescription) {
                @synchronized(self) {
                    CMFormatDescriptionRef formatDescription = CMSampleBufferGetFormatDescription(sampleBuffer);
                    self.manager.outputAudioFormatDescription = formatDescription;
                }
            }
            @synchronized(self) {
                if (self.manager.state == StateRecording) {
                    [self.manager appendBuffer:sampleBuffer type:AVMediaTypeAudio];
                }
            }
        }
    }
}

第4步：AVAssetWriter以及對(duì)應(yīng)的Input

// writer初始化
self.writer = [AVAssetWriter assetWriterWithURL:_videoUrl fileType:AVFileTypeMPEG4 error:nil];

_videoInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:_videoSettings];
//expectsMediaDataInRealTime 必須設(shè)為yes愉阎，需要從capture session 實(shí)時(shí)獲取數(shù)據(jù)
_videoInput.expectsMediaDataInRealTime = YES;

_audioInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeAudio outputSettings:_audioSettings];
_audioInput.expectsMediaDataInRealTime = YES;

if ([_writer canAddInput:_videoInput]) {
    [_writer addInput:_videoInput];
}
if ([_writer canAddInput:_audioInput]) {
    [_writer addInput:_audioInput];
}

第5步：第3步的CMSampleBufferRef通過AVAssetWriter寫入到視頻文件中

- (void)appendBuffer:(CMSampleBufferRef)buffer type:(NSString *)mediaType {
    if (buffer == NULL) {
        NSLog(@"empty sampleBuffer");
        return;
    }
    
    @synchronized (self) {
        if (self.state < StateRecording) {
            NSLog(@"not ready yet");
            return;
        }
    }
    
    CFRetain(buffer);
    dispatch_async(self.queue, ^{
        @autoreleasepool {
            @synchronized (self) {
                if (self.state > StateFinish) {
                    CFRelease(buffer);
                    return;
                }
            }
            
            if (!self.canWrite && mediaType == AVMediaTypeVideo) {
                [self.writer startWriting];
                [self.writer startSessionAtSourceTime:CMSampleBufferGetPresentationTimeStamp(buffer)];
                self.canWrite = YES;
            }
            
            if(!self.timer) {
                dispatch_async(dispatch_get_main_queue(), ^{
                    self.timer = [NSTimer scheduledTimerWithTimeInterval:TIMER_INTERVAL target:self selector:@selector(updateProgress) userInfo:nil repeats:YES];
                    [[NSRunLoop currentRunLoop] addTimer:self.timer forMode:NSDefaultRunLoopMode];
                });
            }
            
            // 寫入視頻數(shù)據(jù)
            if (mediaType == AVMediaTypeVideo) {
                if (self.videoInput.readyForMoreMediaData) {
                    BOOL success = [self.videoInput appendSampleBuffer:buffer];
                    if (!success) {
                        @synchronized (self) {
                            [self stop:^{}];
                            [self destroy];
                        }
                    }
                }
            }
            
            // 寫入音頻數(shù)據(jù)
            if (mediaType == AVMediaTypeAudio) {
                if (self.audioInput.readyForMoreMediaData) {
                    BOOL success = [self.audioInput appendSampleBuffer:buffer];
                    if (!success) {
                        @synchronized (self) {
                            [self stop:^{}];
                            [self destroy];
                        }
                    }
                }
            }
            CFRelease(buffer);
        }
    });
}

寫在末尾：

1. AVAssetWriterInput設(shè)置視頻屬性時(shí)，按照自己的需要設(shè)計(jì)力奋，其中碼率與幀率的設(shè)置會(huì)影響到拍攝后視頻的質(zhì)量與大小榜旦，具體看各自項(xiàng)目的要求

2. 如果視頻視角存在問題，可以從三個(gè)方向入手調(diào)整

   1.layer的connect設(shè)置下videoOrientation

   2.AVCaptureOutput的connect設(shè)置下videoOrientation

   3.AVAssetWriterInput針對(duì)video是設(shè)置下transform景殷，比如Rotation M_PI/2 角度