• 第6月第4天 AVMutableComposition AVMutableVideoComposition


    1.

    AVMutableComposition is a mutable subclass of AVComposition you use when you want to create a new composition from existing assets. You can add and remove tracks, and you can add, remove, and scale time ranges.

     

    AVMutableComposition可以添加删除tracks。

     

            // Check if a composition already exists, else create a composition using the input asset
            self.mutableComposition = [AVMutableComposition composition];
            
            // Insert the video and audio tracks from AVAsset
            if (assetVideoTrack != nil) {
                AVMutableCompositionTrack *compositionVideoTrack = [self.mutableComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
                [compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, [asset duration]) ofTrack:assetVideoTrack atTime:insertionPoint error:&error];
                [compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, [asset duration]) ofTrack:assetVideoTrack atTime:[asset duration] error:&error];
    //            [compositionVideoTrack removeTimeRange:CMTimeRangeMake(kCMTimeZero, CMTimeMakeWithSeconds(1.0, CMTimeGetSeconds([asset duration])))];
            }
            if (assetAudioTrack != nil) {
                AVMutableCompositionTrack *compositionAudioTrack = [self.mutableComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
                [compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, [asset duration]) ofTrack:assetAudioTrack atTime:insertionPoint error:&error];
            }

    The AVMutableVideoComposition class is a mutable subclass of AVVideoComposition.

    A video composition describes, for any time in the aggregate time range of its instructions, the number and IDs of video tracks that are to be used in order to produce a composed video frame corresponding to that time. When AV Foundation’s built-in video compositor is used, the instructions an AVVideoComposition comprises can specify a spatial transformation, an opacity value, and a cropping rectangle for each video source, and these can vary over time via simple linear ramping functions.

    An AVMutableVideoCompositionInstruction object represents an operation to be performed by a compositor.

    An AVVideoComposition object maintains an array of instructions to perform its composition.

    An array of instances of AVVideoCompositionLayerInstruction that specify how video frames from source tracks should be layered and composed.

    Tracks are layered in the composition according to the top-to-bottom order of the layerInstructions array; the track with trackID of the first instruction in the array will be layered on top, with the track with the trackID of the second instruction immediately underneath, and so on.

    If the property value is nil, the output is a fill of the background color.

     

    AVMutableVideoCompositionLayerInstruction is a mutable subclass of AVVideoCompositionLayerInstruction that is used to modify the transform, cropping, and opacity ramps to apply to a given track in a composition. 

     

     

    真正修改track的transform,opacity的是AVMutableVideoCompositionLayerInstruction。AVMutableVideoCompositionInstruction里的一组AVMutableVideoCompositionLayerInstruction,从上到下排列tracks。AVVideoComposition包含一组AVMutableVideoCompositionInstruction。

     

     

                // build a pass through video composition
                self.mutableVideoComposition = [AVMutableVideoComposition videoComposition];
                self.mutableVideoComposition.frameDuration = CMTimeMake(1, 30); // 30 fps
                self.mutableVideoComposition.renderSize = assetVideoTrack.naturalSize;
                
                AVMutableVideoCompositionInstruction *passThroughInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
                passThroughInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, CMTimeAdd([asset duration],([asset duration])));
                
                AVAssetTrack *videoTrack = [self.mutableComposition tracksWithMediaType:AVMediaTypeVideo][0];
                AVMutableVideoCompositionLayerInstruction *passThroughLayer = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:assetVideoTrack];
                [passThroughLayer setOpacity:0 atTime:CMTimeMakeWithSeconds(0.1,600)];
                [passThroughLayer setOpacity:1 atTime:CMTimeMakeWithSeconds(2,600)];
                
    //            [passThroughLayer setTransformRampFromStartTransform:CGAffineTransformIdentity toEndTransform:CGAffineTransformMakeTranslation(-[UIScreen mainScreen].bounds.size.width, 0) timeRange:CMTimeRangeMake(kCMTimeZero, CMTimeMakeWithSeconds(1.0, CMTimeGetSeconds([asset duration])))];
    //            
                passThroughInstruction.layerInstructions = @[passThroughLayer];
                self.mutableVideoComposition.instructions = @[passThroughInstruction];

     2.

    https://developer.apple.com/library/content/samplecode/RosyWriter/Introduction/Intro.html

    1)视频拍摄

    - (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection

    {

     

    2)图像数据

    CVPixelBufferRef sourcePixelBuffer = CMSampleBufferGetImageBuffer( sampleBuffer );

    renderedPixelBuffer = [_renderer copyRenderedPixelBuffer:sourcePixelBuffer];

     

    3)转换数据 写入

    	CMSampleBufferRef sampleBuffer = NULL;
    	
    	CMSampleTimingInfo timingInfo = {0,};
    	timingInfo.duration = kCMTimeInvalid;
    	timingInfo.decodeTimeStamp = kCMTimeInvalid;
    	timingInfo.presentationTimeStamp = presentationTime;
    	
    	OSStatus err = CMSampleBufferCreateForImageBuffer( kCFAllocatorDefault, pixelBuffer, true, NULL, NULL, _videoTrackSourceFormatDescription, &timingInfo, &sampleBuffer );
    	if ( sampleBuffer ) {
    		[self appendSampleBuffer:sampleBuffer ofMediaType:AVMediaTypeVideo];
    		CFRelease( sampleBuffer );
    	}
    
    ...
    			AVAssetWriterInput *input = ( mediaType == AVMediaTypeVideo ) ? _videoInput : _audioInput;
    			
    			if ( input.readyForMoreMediaData )
    			{
    				BOOL success = [input appendSampleBuffer:sampleBuffer];
    				if ( ! success ) {
    					NSError *error = _assetWriter.error;
    					@synchronized( self ) {
    						[self transitionToStatus:MovieRecorderStatusFailed error:error];
    					}
    				}
    			}
    

      

  • 相关阅读:
    100道MySQL数据库经典面试题解析(收藏版)
    input()函数的进阶用法
    MySQL数据库面试题(2020最新版)
    mysql 1418错误_MySQL 错误1418 的原因分析及解决方法
    使用pymysql循环删除重复数据,并修改自增字段偏移值
    字典get方法和setdesault方法,统计message中各元素的出现频次
    Python中字典get方法的使用技巧
    collections模块
    python的30个编程技巧
    SQL中where与having的区别
  • 原文地址:https://www.cnblogs.com/javastart/p/6500789.html
Copyright © 2020-2023  润新知