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iOS拍个小视频

  • 需求

    公司混合开发,uni端拍小视频不是很理想,为达到仿微信效果,原生插件走起

  • 思路

    第1步:1个AVCaptureSession, 1块AVCaptureVideoPreviewLayer[考虑兼容替换成AVPreView]

    第2步:视频录制需video & audio, 需要对应的AVCaptureDeviceInput,同理对应的AVCaptureVideoDataOutput与AVCaptureAudioDataOutput

    第3步:代理中设置output区分video与audio, 并将对应的CMSampleBufferRef写入到视频文件中

    第4步:写入视频文件中,用到AVAssetWriter, 对应video & audio 需两个AVAssetWriterInput, 加入AVAssetWriter

    第5步:CMSampleBufferRef不断过来,AssetWriter不断写入,直到停止

  • 上菜

    第一步的初始化就不写了,没事可以翻看本人前面的博客

    第2步:两个AVCaptureDeviceInput 两个Output, 且设置Output的代理

    self.videoInput = [[AVCaptureDeviceInput alloc] initWithDevice:device error:&error];
    if (error) {
        NSLog(@"取得设备摄入videoInput对象时出错, 错误原因: %@", error);
        return;
    }
    
    // 设备添加到会话中
    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];
    }
    
    // 音频相关
    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];
    }
    
    // 视频输出
    - (AVCaptureVideoDataOutput *)videoOutput {
        if (!_videoOutput) {
            _videoOutput = [[AVCaptureVideoDataOutput alloc] init];
            _videoOutput.alwaysDiscardsLateVideoFrames = YES;
        }
        return _videoOutput;
    }
    
    // 音频输出
    - (AVCaptureAudioDataOutput *)audioOutput {
        if (!_audioOutput) {
            _audioOutput = [[AVCaptureAudioDataOutput alloc] init];
        }
        return _audioOutput;
    }
    
    复制代码

    第3步:启动Session,代理里面操作CMSampleBufferRef

    #pragma mark - AVCaptureVideoDataOutputSampleBufferDelegate & AVCaptureAudioDataOutputSampleBufferDelegate
    - (void)captureOutput:(AVCaptureOutput *)output didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
        @autoreleasepool {
            // 视频
            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];
                        }
                    }
                }
            }
            
            //音频
            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];
                    }
                }
            }
        }
    }
    复制代码

    第4步:AVAssetWriter以及对应的Input

    // writer初始化
    self.writer = [AVAssetWriter assetWriterWithURL:_videoUrl fileType:AVFileTypeMPEG4 error:nil];
    
    _videoInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:_videoSettings];
    //expectsMediaDataInRealTime 必须设为yes,需要从capture session 实时获取数据
    _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];
    }
    复制代码

    第5步:第3步的CMSampleBufferRef通过AVAssetWriter写入到视频文件中

    - (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];
                    });
                }
                
                // 写入视频数据
                if (mediaType == AVMediaTypeVideo) {
                    if (self.videoInput.readyForMoreMediaData) {
                        BOOL success = [self.videoInput appendSampleBuffer:buffer];
                        if (!success) {
                            @synchronized (self) {
                                [self stop:^{}];
                                [self destroy];
                            }
                        }
                    }
                }
                
                // 写入音频数据
                if (mediaType == AVMediaTypeAudio) {
                    if (self.audioInput.readyForMoreMediaData) {
                        BOOL success = [self.audioInput appendSampleBuffer:buffer];
                        if (!success) {
                            @synchronized (self) {
                                [self stop:^{}];
                                [self destroy];
                            }
                        }
                    }
                }
                CFRelease(buffer);
            }
        });
    }
    
    复制代码
  • 写在末尾:

    1. AVAssetWriterInput设置视频属性时,按照自己的需要设计,其中码率与帧率的设置会影响到拍摄后视频的质量与大小,具体看各自项目的要求

    2. 如果视频视角存在问题,可以从三个方向入手调整

      1.layer的connect设置下videoOrientation

      2.AVCaptureOutput的connect设置下videoOrientation

      3.AVAssetWriterInput针对video是设置下transform,比如Rotation M_PI/2 角度

文章分类
iOS
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