oc视频抽取

视频抽取

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+ (void)drawFramesFromVideoAtPath:(NSString *)videoPath toDirectory:(NSString *)outPath withTargetFrame:(NSUInteger)targetFrame {
    DLog(@"-------------------------视频抽帧-------------------------");

    NSFileManager *fileManager = [NSFileManager defaultManager];
    NSError *error = nil;
    if (![fileManager fileExistsAtPath:outPath]) {
        // 判断文件夹是否存在
        [fileManager createDirectoryAtPath:outPath withIntermediateDirectories:YES attributes:nil error:&error];
        if (error) {
            DLog(@"创建输出目录失败：%@", error);
            return;
        }
    }

    NSURL *videoURL = [NSURL fileURLWithPath:videoPath];
    AVAsset *asset = [AVAsset assetWithURL:videoURL];
    AVAssetTrack *videoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] firstObject];
    NSUInteger frames = CMTimeGetSeconds(asset.duration) * videoTrack.nominalFrameRate;
    DLog(@"视频共%lu帧，抽取%lu帧......", (unsigned long)frames, (unsigned long)(frames / targetFrame) + 1);

    AVAssetReader *assetReader = [AVAssetReader assetReaderWithAsset:asset error:&error];
    if (error) {
        DLog(@"创建AVAssetReader失败：%@", error);
        return;
    }

    AVAssetReaderTrackOutput *output = [AVAssetReaderTrackOutput assetReaderTrackOutputWithTrack:videoTrack outputSettings:@{
        (NSString *)kCVPixelBufferPixelFormatTypeKey : @(kCVPixelFormatType_32BGRA)
    }];
    [assetReader addOutput:output];
    [assetReader startReading];

    NSUInteger count = 0;
    NSUInteger imageIndex = 1000001;
    while (assetReader.status == AVAssetReaderStatusReading) {
        CMSampleBufferRef sampleBuffer = [output copyNextSampleBuffer];
        if (sampleBuffer == NULL) {
            break;
        }

        if (count % targetFrame == 0 || count == frames - 1) {
            DLog(@"已提取 %d", (imageIndex - 1000000));
            @autoreleasepool
            {
                UIImage *uiImage = [self convertSampleBufferRefToUIImage:sampleBuffer];
                NSString *savePath = [outPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%lu.png", (unsigned long)imageIndex]];
                @autoreleasepool {
                    NSData *imageData = UIImagePNGRepresentation(uiImage);
                    [imageData writeToFile:savePath atomically:YES];
                }
            }
            imageIndex++;
        }
        count++;
        CFRelease(sampleBuffer);
    }

    if (assetReader.status == AVAssetReaderStatusCompleted) {
        DLog(@"视频已全部抽帧完成......");
    } else if (assetReader.status == AVAssetReaderStatusFailed) {
        DLog(@"抽帧失败：%@", assetReader.error);
    } else if (assetReader.status == AVAssetReaderStatusCancelled) {
        DLog(@"抽帧被取消");
    }

    DLog(@"-------------------------抽帧完成-------------------------");
}


+ (UIImage *)convertSampleBufferRefToUIImage:(CMSampleBufferRef)sampleBufferRef
{
    @autoreleasepool
    {
        CGImageRef cgImage = [self convertSamepleBufferRefToCGImage:sampleBufferRef];
        UIImage *image;

        CGFloat height = CGImageGetHeight(cgImage);
        CGFloat width = CGImageGetWidth(cgImage);

//        height = height / 5;
//        width = width / 5;

        UIGraphicsBeginImageContextWithOptions(CGSizeMake(width, height), NO, 1);

#define UseUIImage 0
#if UseUIImage

        [image drawInRect:CGRectMake(0, 0, width, height)];
#else
        CGContextRef context = UIGraphicsGetCurrentContext();
        CGContextTranslateCTM(context, 0, height);
        CGContextScaleCTM(context, 1.0, -1.0);
        CGContextDrawImage(context, CGRectMake(0, 0, width, height), cgImage);
#endif
        image = UIGraphicsGetImageFromCurrentImageContext();

        UIGraphicsEndImageContext();

        CGImageRelease(cgImage);

//        UIGraphicsEndImageContext();
        return image;
    }
}


// Create a UIImage from sample buffer data
// 官方回答 https://developer.apple.com/library/ios/qa/qa1702/_index.html
+ (CGImageRef)convertSamepleBufferRefToCGImage:(CMSampleBufferRef)sampleBufferRef {
    @autoreleasepool {

        // Get a CMSampleBuffer's Core Video image buffer for the media data
        CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBufferRef);
        // Lock the base address of the pixel buffer
        CVPixelBufferLockBaseAddress(imageBuffer, 0);

        // Get the number of bytes per row for the pixel buffer
        void *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer);

        // Get the number of bytes per row for the pixel buffer
        size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
        // Get the pixel buffer width and height
        size_t width = CVPixelBufferGetWidth(imageBuffer);
        size_t height = CVPixelBufferGetHeight(imageBuffer);

        // Create a device-dependent RGB color space
        CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

        // Create a bitmap graphics context with the sample buffer data
        CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8,
                                                     bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
        // Create a Quartz image from the pixel data in the bitmap graphics context
        CGImageRef quartzImage = CGBitmapContextCreateImage(context);
        // Unlock the pixel buffer
        CVPixelBufferUnlockBaseAddress(imageBuffer,0);

        // Free up the context and color space
        CGContextRelease(context);
        CGColorSpaceRelease(colorSpace);

        return quartzImage;
    }
}