AVFoundation reverse play 倒放實(shí)現(xiàn)

一.參考:

http://www.andyhin.com/post/5/reverse-video-avfoundation

二.幾種實(shí)現(xiàn)方案思路

1.預(yù)覽過程使用AVPlayer的倒放功能

設(shè)置AVPlayer的rate 為-1
檢查AVPlayerItem的canPlayReverse是否是YES

由于我們采用的GPUImage框架,在預(yù)覽過程沒有使用AVPlayer,次方案沒有繼續(xù)調(diào)研

2.使用AVAssetComposition把每幀位置翻轉(zhuǎn)

速度快,不生成臨時(shí)文件
必須每幀都是關(guān)鍵幀 否則嚴(yán)重卡頓 掉幀
無法精確控制insert單幀TimeRange

3.修改GPUImageMovie 倒序讀取CVPixelBuffer (不可行)

基于AVPlayerItemVideoOutput copyPixelBufferForItemTime方法,嘗試倒序copy.
實(shí)驗(yàn)發(fā)現(xiàn)該函數(shù)貌似不支持倒序讀取,倒序讀取前幾秒返回正序的pixelBuffer,之后始終返回空.閱讀函數(shù)文檔也證明了這點(diǎn).

4.使用AVAssetReader AVAssetWriter 讀取出每個(gè)CMSampleBuffer反向?qū)懭胛募?(可行)

播放非常流暢.
但需要生成臨時(shí)文件,處理時(shí)間較長.

三.AVAssetReader AVAssetWriter倒序視頻方案實(shí)現(xiàn)

AHSVVideoReverse.h

//
//  AHSVVideoReverse.h
//  AHVideoSDKFramework
//
//  Created by 李田迎 on 2019/8/13.
//  Copyright ? 2019 Autohome. All rights reserved.
//

#import <Foundation/Foundation.h>
#import <AVFoundation/AVFoundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface AHSVVideoReverse : NSObject

@property (nonatomic, copy) NSDictionary *videoSettings;            //!< 寫入視頻配置參數(shù) 有默認(rèn)參數(shù)
@property (strong, nonatomic) NSDictionary *readerOutputSettings;   //!< 視頻軌道讀取出的數(shù)據(jù)格式

/**
 根據(jù)原始視頻生成倒放視頻

 @param origAsset 被倒放視頻asset
 @param outputPath 倒放的視頻存儲(chǔ)路徑
 @param handler 回調(diào)信息block
 */
- (void)reverseVideo:(AVAsset *)origAsset
          outputPath:(NSString *)outputPath
       completeBlock:(void (^)(NSError *error))handler;
@end

NS_ASSUME_NONNULL_END

AHSVVideoReverse.m

//
//  AHSVVideoReverse.m
//  AHVideoSDKFramework
//
//  Created by 田迎 on 2019/8/13.
//  Copyright ? 2019. All rights reserved.
//

#import "AHSVVideoReverse.h"
#import "AVAsset+Addition.h"
#import "AHVideoRecordCustomConfig.h"

#define kClipMaxContainCount 10

@interface AHSVVideoReverse ()
@property (nonatomic, strong) AVAsset *origAsset;                   //!< 原始資源對象
@property (nonatomic, strong) AVAssetReader *assetReader;           //!< 資源讀取對象
@property (nonatomic, strong) AVAssetWriter *assetWriter;           //!< 多媒體文件寫入
@property (nonatomic, strong) AVAssetWriterInput *videoWriterInput; //!< 視頻寫入 append
@property (nonatomic, strong) AVAssetReaderTrackOutput *videoTrackOutput;   //!< 視頻輸出對象
//adapter 有CVPixelBufferPool緩沖池提高寫入效率 可以寫入CVPixelBuffer 和時(shí)間戳
@property (nonatomic, strong) AVAssetWriterInputPixelBufferAdaptor *videoPixelBufferAdaptor;

@property (nonatomic, strong) NSURL *outputURL;                     //!< 輸出文件Url
@property (nonatomic, strong) dispatch_queue_t inputQueue;          //!< 多媒體數(shù)據(jù)寫入隊(duì)列
@property (nonatomic, assign) CGSize targetSize;                    //!< 導(dǎo)出視頻size
@property (nonatomic, assign) float fps;                            //!< 幀率
@property (nonatomic, strong) void (^completionHandler)(NSError *); //!< 回調(diào)block
//內(nèi)部邏輯使用
@property (nonatomic, strong) NSMutableArray *sampleTimeArray;      //!< 存儲(chǔ)采樣時(shí)間戳數(shù)組
@property (nonatomic, strong) NSMutableArray *clipTimeRangeArray;   //!< 分段處理時(shí)間段數(shù)組
@end

@implementation AHSVVideoReverse

#pragma mark -
#pragma mark LifeCycle Method
- (instancetype)init {
    if (self = [super init]) {
        
    }
    
    return self;
}

- (void)dealloc {
    
}

#pragma mark -
#pragma mark Public Method
- (void)reverseVideo:(AVAsset *)origAsset
          outputPath:(NSString *)outputPath
       completeBlock:(void (^)(NSError *error))handler {
    
    self.completionHandler = handler;
    
    if (!origAsset) {
        NSError *error = [NSError errorWithDomain:@"com.avvideo.videoReverse" code:-100 userInfo:@{@"msg":@"參數(shù)origAsset 不能為空!"}];
        self.completionHandler(error);
        
        return;
    }
    
    if (!origAsset.videoTrack) {
        NSError *error = [NSError errorWithDomain:@"com.avvideo.videoReverse" code:-101 userInfo:@{@"msg":@"origAsset中不含有視頻軌道信息!"}];
        self.completionHandler(error);
        
        return;
    }
    
    if (!outputPath || outputPath.length==0) {
        NSError *error = [NSError errorWithDomain:@"com.avvideo.videoReverse" code:-102 userInfo:@{@"msg":@"參數(shù)outputPath 不能為空!"}];
        self.completionHandler(error);
        
        return;
    }
    
    self.outputURL = [NSURL fileURLWithPath:outputPath];
    //本地目標(biāo)文件清理
    if ([[NSFileManager defaultManager] fileExistsAtPath:outputPath]) {
        [[NSFileManager defaultManager] removeItemAtPath:outputPath error:nil];
    }
    
    self.origAsset = origAsset;
    
    WEAKSELF;
    [self.origAsset loadValuesAsynchronouslyForKeys:@[@"duration", @"tracks"] completionHandler:^{
        dispatch_async(weakSelf.inputQueue, ^{
            [weakSelf startReverseProcess];
        });
    }];
}

#pragma mark -
#pragma mark Private Method

- (void)startReverseProcess {
    [self cancelRevese];
    self.targetSize = self.origAsset.videoTrackSize;
    self.fps = self.origAsset.videoTrack.nominalFrameRate;

    //1. 生成每幀時(shí)間數(shù)組與分段數(shù)組
    [self generateSampleTimesArray];
    //2. 處理所有分段 正序讀取 倒序?qū)懭?    [self processReadReverseWriter];
}

//生成每幀時(shí)間數(shù)組 用于獲取倒序時(shí)每個(gè)CVPixelBuffer的精確時(shí)間戳 以及分段數(shù)組
- (void)generateSampleTimesArray {
    if ([self.assetReader canAddOutput:self.videoTrackOutput]) {
        [self.assetReader addOutput:self.videoTrackOutput];
    }
    [self.assetReader startReading];
    
    CMSampleBufferRef sample;
    NSUInteger processIndex = 0;
    CMTime startTime = kCMTimeZero;
    CMTime endTime = kCMTimeZero;
    CMTime presentationTime = kCMTimeZero;
    
    while((sample = [self.videoTrackOutput copyNextSampleBuffer])) {
        presentationTime = CMSampleBufferGetPresentationTimeStamp(sample);
        NSValue *presentationValue = [NSValue valueWithBytes:&presentationTime objCType:@encode(CMTime)];
        [self.sampleTimeArray addObject:presentationValue];
        
        CFRelease(sample);
        sample = NULL;
        
        if (processIndex == 0) {
            startTime = presentationTime;
            processIndex ++;
            
        } else if (processIndex == kClipMaxContainCount-1) {
            endTime = presentationTime;
            
            CMTimeRange timeRange = CMTimeRangeMake(startTime, CMTimeSubtract(endTime, startTime));
            NSValue *timeRangeValue = [NSValue valueWithCMTimeRange:timeRange];
            [self.clipTimeRangeArray addObject:timeRangeValue];
            
            processIndex = 0;
            startTime = kCMTimeZero;
            endTime = kCMTimeZero;
            
        } else {
            processIndex ++;
        }
    }
    
    //處理不夠kClipMaxContainCount數(shù)量的幀的timerange
    if (CMTIME_COMPARE_INLINE(kCMTimeZero, !=, startTime) && CMTIME_COMPARE_INLINE(kCMTimeZero, ==, endTime)) {
        
        endTime = presentationTime;
        
        //單獨(dú)處理最后只剩一幀的情況
        if (CMTIME_COMPARE_INLINE(endTime, ==, startTime) &&
            processIndex == 1) {
            startTime = CMTimeSubtract(startTime, CMTimeMake(1, self.fps));
        }
        
        CMTimeRange timeRange = CMTimeRangeMake(startTime, CMTimeSubtract(endTime, startTime));
        NSValue *timeRangeValue = [NSValue valueWithCMTimeRange:timeRange];
        [self.clipTimeRangeArray addObject:timeRangeValue];
    }
}

- (void)processReadReverseWriter {
    CMSampleBufferRef sampleBuffer;
    
    //1.保護(hù)處理 清理之前可能未讀取完的數(shù)據(jù)
    while((sampleBuffer = [self.videoTrackOutput copyNextSampleBuffer])) {
        CFRelease(sampleBuffer);
    }
    
    //2.為asserWriter添加writerInput 開始讀寫操作
    if ([self.assetWriter canAddInput:self.videoWriterInput]) {
        [self.assetWriter addInput:self.videoWriterInput];
    }
    [self videoPixelBufferAdaptor];
    BOOL success = [self.assetWriter startWriting];
    if (!success) {
        NSLog(@"self.assetWriter error = %@", self.assetWriter.error);
    }
    [self.assetWriter startSessionAtSourceTime:kCMTimeZero];
    
    NSUInteger clipCount = self.clipTimeRangeArray.count;
    //當(dāng)前處理幀索引
    NSUInteger frameIndex = 0;
    for (NSInteger i=clipCount-1; i>=0; i--) {
        
        NSValue *clipTimeRangeValue = [self.clipTimeRangeArray objectAtIndex:i];
        [self.videoTrackOutput resetForReadingTimeRanges:@[clipTimeRangeValue]];
        
        //讀取分段中所有幀到緩存數(shù)組
        NSMutableArray *tempSampleArray = [[NSMutableArray alloc] init];
        while((sampleBuffer = [self.videoTrackOutput copyNextSampleBuffer])) {
            [tempSampleArray addObject:(__bridge id)sampleBuffer];
            CFRelease(sampleBuffer);
        }
        
        //每個(gè)分段內(nèi)的幀 倒序?qū)懭雡riter
        for (NSInteger j=0; j<tempSampleArray.count; j++) {
            //保護(hù)處理
            if (frameIndex >= self.sampleTimeArray.count) {
                continue;
            }
            NSValue *timeValue = [self.sampleTimeArray objectAtIndex:frameIndex];
            CMTime frameTime = [timeValue CMTimeValue];
//            CMTimeShow(frameTime);
            CVPixelBufferRef pixefBuffer = CMSampleBufferGetImageBuffer((__bridge CMSampleBufferRef)tempSampleArray[tempSampleArray.count - j - 1]);
            
            // append frames to output
            BOOL appendSuccess = NO;
            while (!appendSuccess) {
                if (self.videoPixelBufferAdaptor.assetWriterInput.readyForMoreMediaData) {
                    appendSuccess = [self.videoPixelBufferAdaptor appendPixelBuffer:pixefBuffer withPresentationTime:frameTime];
                    
                    if (!appendSuccess) {
                        NSLog(@"appendPixelBuffer error at time: %lld", frameTime.value);
                    } else {
                        // NSLog(@"appendPixelBuffer success at time: %f", CMTimeGetSeconds(frameTime));
                    }
                
                } else {
                    // adaptor not ready
                    [NSThread sleepForTimeInterval:0.05];
                }
            }
            
            frameIndex ++;
        }
    }
    
    [self.videoWriterInput markAsFinished];
    WEAKSELF;
    [self.assetWriter finishWritingWithCompletionHandler:^(){
        if (weakSelf.completionHandler) {
            weakSelf.completionHandler(nil);
        }
    }];
}

- (void)cancelRevese {
    if (!_inputQueue) {
        return;
    }
    
    if (_assetReader && _assetReader.status == AVAssetReaderStatusReading) {
        [self.assetReader cancelReading];
    }
    _assetReader = nil;
    
    if (_assetWriter && _assetWriter.status == AVAssetWriterStatusWriting) {
        [self.assetWriter cancelWriting];
    }
    _assetWriter = nil;
    
    if (_videoTrackOutput) {
        _videoTrackOutput = nil;
    }
    
    if (_videoWriterInput) {
        _videoWriterInput = nil;
    }
    
    if (_videoPixelBufferAdaptor) {
        _videoPixelBufferAdaptor = nil;
    }
    
    if (_clipTimeRangeArray) {
        _clipTimeRangeArray = nil;
    }
    
    if (_sampleTimeArray) {
        _sampleTimeArray = nil;
    }
}


#pragma mark -
#pragma mark Get Method
- (AVAssetReader *)assetReader {
    if (!_assetReader) {
        NSError *error;
        _assetReader = [[AVAssetReader alloc] initWithAsset:self.origAsset error:&error];
        if (error) {
            NSLog(@"assetReader 創(chuàng)建失敗!! %@", error);
        }
    }
    
    return _assetReader;
}

- (AVAssetWriter *)assetWriter {
    if (!_assetWriter) {
        NSError *writerError;
        _assetWriter = [AVAssetWriter assetWriterWithURL:self.outputURL fileType:AVFileTypeQuickTimeMovie error:&writerError];
        _assetWriter.shouldOptimizeForNetworkUse = YES;
        if (writerError) {
            NSLog(@"assetWriter 創(chuàng)建失敗 %@", writerError);
        }
    }
    
    return _assetWriter;
}

- (AVAssetReaderTrackOutput *)videoTrackOutput {
    if (!_videoTrackOutput) {
        _videoTrackOutput = [AVAssetReaderTrackOutput assetReaderTrackOutputWithTrack:self.origAsset.videoTrack outputSettings:self.readerOutputSettings];
        //設(shè)置支持不按順序讀取數(shù)據(jù) 設(shè)置為YES后 resetForReadingTimeRanges方法才可用
        _videoTrackOutput.supportsRandomAccess = YES;
        //不需要修改sample中的CVPixelBuffer內(nèi)容 所以不需要copy
        _videoTrackOutput.alwaysCopiesSampleData = NO;
    }
    
    return _videoTrackOutput;
}

- (AVAssetWriterInput *)videoWriterInput {
    if (!_videoWriterInput) {
        _videoWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:self.videoSettings];
        _videoWriterInput.expectsMediaDataInRealTime = NO;
        [_videoWriterInput setTransform:self.origAsset.videoTrack.preferredTransform];
    }
    
    return _videoWriterInput;
}

- (AVAssetWriterInputPixelBufferAdaptor *)videoPixelBufferAdaptor {
    if (!_videoPixelBufferAdaptor) {
        NSDictionary *pixelBufferAttributes = @{
                                                (id)kCVPixelBufferPixelFormatTypeKey: @(kCVPixelFormatType_32BGRA),
                                                (id)kCVPixelBufferWidthKey: @(self.targetSize.width),
                                                (id)kCVPixelBufferHeightKey: @(self.targetSize.height),
                                                @"IOSurfaceOpenGLESTextureCompatibility": @YES,
                                                @"IOSurfaceOpenGLESFBOCompatibility": @YES,
                                                };
        _videoPixelBufferAdaptor = [AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:self.videoWriterInput sourcePixelBufferAttributes:pixelBufferAttributes];
    }
    
    return _videoPixelBufferAdaptor;
}

- (NSDictionary *)readerOutputSettings {
    if (!_readerOutputSettings) {
        _readerOutputSettings = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInt:kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange], kCVPixelBufferPixelFormatTypeKey, nil];
    }
    
    return _readerOutputSettings;
}

- (dispatch_queue_t)inputQueue {
    if (!_inputQueue) {
        _inputQueue = dispatch_queue_create("com.ahvideo.reverseInputQueue", DISPATCH_QUEUE_SERIAL);
    }
    
    return _inputQueue;
}

- (NSDictionary *)videoSettings {
    if (!_videoSettings) {
        _videoSettings = @{AVVideoCodecKey: AVVideoCodecH264,
                           AVVideoWidthKey: @(self.targetSize.width),
                           AVVideoHeightKey: @(self.targetSize.height),
                           AVVideoCompressionPropertiesKey: @{
                                   AVVideoAverageBitRateKey: @(kDefaultVideoBitRate * 1000),
                                   AVVideoExpectedSourceFrameRateKey : @(kDefaultVideoFrameRate),
                                   AVVideoMaxKeyFrameIntervalKey : @(kDefaultVideoKeyFrameInterval),
                                   AVVideoProfileLevelKey: kDefaultVideoProfileLevel
                                   },
                           };
    }
    
    return _videoSettings;
}

- (NSMutableArray *)sampleTimeArray {
    if (!_sampleTimeArray) {
        _sampleTimeArray = [[NSMutableArray alloc] initWithCapacity:100];
    }
    
    return _sampleTimeArray;
}

- (NSMutableArray *)clipTimeRangeArray {
    if (!_clipTimeRangeArray) {
        _clipTimeRangeArray = [[NSMutableArray alloc] initWithCapacity:20];
    }
    
    return _clipTimeRangeArray;
}

#pragma mark -
#pragma mark Set Method
@end