上一篇使用AVFilter把YUV数据转换成RGB数据然后显示，这一篇省去转换过程直接使用CoreImage显示YUV数据

解码代码

去掉之前的AVFilter相关代码

- (void)decodeVideo {
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{  //在全局队列中解码
        AVPacket * packet = av_packet_alloc();
        if (av_read_frame(self->pFormatCtx, packet) >= 0) {
            if (packet->stream_index == self->videoIndex) {  //解码视频流
                //FFmpeg 3.0之后avcodec_send_packet和avcodec_receive_frame成对出现用于解码，包括音频和视频的解码，avcodec_decode_video2和avcodec_decode_audio4被废弃
                NSInteger ret = avcodec_send_packet(self->pCodecCtx, packet);
                if (ret < 0) {
                    NSLog(@"send packet error");
                    av_packet_free(&packet);
                    return;
                }
                AVFrame * frame = av_frame_alloc();
                ret = avcodec_receive_frame(self->pCodecCtx, frame);
                if (ret < 0) {
                    NSLog(@"receive frame error");
                    av_frame_free(&frame);
                    return;
                }
                 //frame中data存放解码出的yuv数据，data[0]中是y数据，data[1]中是u数据，data[2]中是v数据，linesize对应的数据长度
                float time = packet->pts * av_q2d(self->pFormatCtx->streams[self->videoIndex]->time_base);  //计算当前帧时间
                av_packet_free(&packet);

                CVReturn theError;
                if (!self->pixelBufferPool){  //创建pixelBuffer缓存池，从缓存池中创建pixelBuffer以便复用
                    NSMutableDictionary* attributes = [NSMutableDictionary dictionary];
                    [attributes setObject:[NSNumber numberWithInt:kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange] forKey:(NSString*)kCVPixelBufferPixelFormatTypeKey];
                    [attributes setObject:[NSNumber numberWithInt:frame->width] forKey: (NSString*)kCVPixelBufferWidthKey];
                    [attributes setObject:[NSNumber numberWithInt:frame->height] forKey: (NSString*)kCVPixelBufferHeightKey];
                    [attributes setObject:@(frame->linesize[0]) forKey:(NSString*)kCVPixelBufferBytesPerRowAlignmentKey];
                    [attributes setObject:[NSDictionary dictionary] forKey:(NSString*)kCVPixelBufferIOSurfacePropertiesKey];
                    theError = CVPixelBufferPoolCreate(kCFAllocatorDefault, NULL, (__bridge CFDictionaryRef) attributes, &self->pixelBufferPool);
                    if (theError != kCVReturnSuccess){
                        NSLog(@"CVPixelBufferPoolCreate Failed");
                    }
                }

                CVPixelBufferRef pixelBuffer = nil;
                theError = CVPixelBufferPoolCreatePixelBuffer(NULL, self->pixelBufferPool, &pixelBuffer);
                if(theError != kCVReturnSuccess){
                    NSLog(@"CVPixelBufferPoolCreatePixelBuffer Failed");
                }

                theError = CVPixelBufferLockBaseAddress(pixelBuffer, 0);
                if (theError != kCVReturnSuccess) {
                    NSLog(@"lock error");
                }
                /*
                 PixelBuffer中Y数据存放在Plane0中，UV数据存放在Plane1中，数据格式如下
                 frame->data[0]  .........   YYYYYYYYY
                 frame->data[1]  .........   UUUUUUUU
                 frame->data[2]  .........   VVVVVVVVV
                 PixelBuffer->Plane0 .......  YYYYYYYY
                 PixelBuffer->Plane1 .......  UVUVUVUVUV
                 所以需要把Y数据拷贝到Plane0上，把U和V数据交叉拷贝到Plane1上
                 */
                size_t bytePerRowY = CVPixelBufferGetBytesPerRowOfPlane(pixelBuffer, 0);
                size_t bytesPerRowUV = CVPixelBufferGetBytesPerRowOfPlane(pixelBuffer, 1);
                //获取Plane0的起始地址
                void* base = CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 0);
                memcpy(base, frame->data[0], bytePerRowY * frame->height);
                //获取Plane1的起始地址
                base = CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 1);
                uint32_t size = frame->linesize[1] * frame->height / 2;
                //把UV数据交叉存储到dstData然后拷贝到Plane1上
                uint8_t* dstData = new uint8_t[2 * size];
                uint8_t * firstData = new uint8_t[size];
                memcpy(firstData, frame->data[1], size);
                uint8_t * secondData  = new uint8_t[size];
                memcpy(secondData, frame->data[2], size);
                for (int i = 0; i < 2 * size; i++){
                    if (i % 2 == 0){
                        dstData[i] = firstData[i/2];
                    }else {
                        dstData[i] = secondData[i/2];
                    }
                }
                memcpy(base, dstData, bytesPerRowUV * frame->height/2);
                CVPixelBufferUnlockBaseAddress(pixelBuffer, 0);
                av_frame_free(&frame);
                free(dstData);
                free(firstData);
                free(secondData);

                CIImage *coreImage = [CIImage imageWithCVPixelBuffer:pixelBuffer];
                //避免频繁的创建CIContext，所以把context设为全局变量并初始化self->context = [CIContext contextWithOptions:nil];
                CGImageRef videoImage = [self->context createCGImage:coreImage
                                                                   fromRect:CGRectMake(0, 0, self->pCodecCtx->width, self->pCodecCtx->height)];
                NSImage * image = [[NSImage alloc] initWithCGImage:videoImage size:NSSizeFromCGSize(CGSizeMake(self->pCodecCtx->width, self->pCodecCtx->height))];
                CVPixelBufferRelease(pixelBuffer);
                CGImageRelease(videoImage);
                dispatch_async(dispatch_get_main_queue(), ^{
                    self.label.stringValue = [NSString stringWithFormat:@"%.2d:%.2d", (int)time/60, (int)time%60];
                    self.imageView.image = image;
                    self.slider.floatValue = time / (float)self->videoDuration;
                });
            }
        } else {
            avcodec_free_context(&self->pCodecCtx);
            avformat_close_input(&self->pFormatCtx);
            avformat_free_context(self->pFormatCtx);
            [self->timer invalidate];
        }
    });
}