FFMPEG--使用Filter实现YUV图像翻转

工具：ffmpeg过滤器模块
相关过滤器，其创建过程如下：
创建一个过滤器节点，如overlay：avfilter_get_by_name(“overlay”);
创建一个过滤器上下文并将其添加到FilterGraph上，如：avfilter_graph_create_filter(&overlayFilter_ctx, overlayFilter, “overlay”,
“y=0:H/2”, NULL, filter_graph)；
    // overlay filter：视频合成
    AVFilter *overlayFilter = avfilter_get_by_name("overlay");
    AVFilterContext *overlayFilter_ctx;
    ret = avfilter_graph_create_filter(&overlayFilter_ctx, overlayFilter, "overlay",
                                       "y=0:H/2", NULL, filter_graph);

buffer（源过滤器）
buffersink（输出过滤器）
split（分流）
参数配置如：“outputs=2”
crop（裁剪）
参数配置裁剪区域：“out_w=iw:out_h=ih/2:x=0:y=0”
vfilpt（垂直翻转）
无需参数
overlay（视频合成）
将通过滤镜的图像叠加到某个位置：“y=0:H/2”
代码如下，整体流程均已注释：
#include <stdio.h>

#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
//#include <libavfilter/avfiltergraph.h>
#include <libavfilter/avfilter.h>
#include <libavfilter/buffersink.h>
#include <libavfilter/buffersrc.h>
#include <libavutil/opt.h>
#include <libavutil/imgutils.h>

int main(int argc, char* argv)
{
    int ret = 0;

    // input yuv
    FILE* inFile = NULL;
    const char* inFileName = "F:\\Avenger4_1_YUV420P_480x320.yuv";
    //errno_t Errno = fopen_s(&inFile, inFileName, "rb+");
    inFile = fopen(inFileName, "rb");
    if (!inFile) {
        printf("Fail to open file\n");
        return -1;
    }

    int in_width = 480;
    int in_height = 320;

    // output yuv
    FILE* outFile = NULL;
    const char* outFileName = "F:\\out_crop_vfilter_480x320.yuv";
    fopen_s(&outFile, outFileName, "wb");
    if (!outFile) {
        printf("Fail to create file for output\n");
        return -1;
    }

    //1.注册过滤器
    avfilter_register_all();

    //2.创建一个过滤器图层，管理所有过滤器
    AVFilterGraph* filter_graph = avfilter_graph_alloc();
    if (!filter_graph) {
        printf("Fail to create filter graph!\n");
        return -1;
    }

    //3.获取一个用于AVFilterGraph输入的过滤器
    // source filter，源头过滤器，过滤器参数 一般为图像格式信息
    char args[512];
    sprintf(args,
        "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
        in_width, in_height, AV_PIX_FMT_YUV420P, 1, 25, 1, 1);
    //bufferSrc->description = Buffer video frames, and make them accessible to the filterchain.
    AVFilter* bufferSrc = avfilter_get_by_name("buffer");   // AVFilterGraph的输入源

    AVFilterContext* bufferSrc_ctx;
    ret = avfilter_graph_create_filter(&bufferSrc_ctx, bufferSrc, "in", args, NULL, filter_graph);
    if (ret < 0) {
        printf("Fail to create filter bufferSrc\n");
        return -1;
    }

    //4.获取一个用于AVFilterGraph输出的过滤器
    // sink filter，
    AVBufferSinkParams *bufferSink_params;
    AVFilterContext* bufferSink_ctx;
    AVFilter* bufferSink = avfilter_get_by_name("buffersink");
    enum AVPixelFormat pix_fmts[] = { AV_PIX_FMT_YUV420P, AV_PIX_FMT_NONE };

    bufferSink_params = av_buffersink_params_alloc();
    bufferSink_params->pixel_fmts = pix_fmts;
    ret = avfilter_graph_create_filter(&bufferSink_ctx, bufferSink, "out", NULL,
                                       bufferSink_params, filter_graph);
    if (ret < 0) {
        printf("Fail to create filter sink filter\n");
        return -1;
    }

    //5. split filter：用于分流，outputs=2表示输出两股流
    AVFilter *splitFilter = avfilter_get_by_name("split");
    AVFilterContext *splitFilter_ctx;
    ret = avfilter_graph_create_filter(&splitFilter_ctx, splitFilter, "split", "outputs=2",
                                       NULL, filter_graph);
    if (ret < 0) {
        printf("Fail to create split filter\n");
        return -1;
    }

    //6. crop filter：裁剪，out_w=iw:out_h=ih/2:x=0:y=0表示裁剪得到的区域
    AVFilter *cropFilter = avfilter_get_by_name("crop");
    AVFilterContext *cropFilter_ctx;
    ret = avfilter_graph_create_filter(&cropFilter_ctx, cropFilter, "crop",
                                       "out_w=iw:out_h=ih/2:x=0:y=0", NULL, filter_graph);
    if (ret < 0) {
        printf("Fail to create crop filter\n");
        return -1;
    }

    //7. vflip filter：垂直翻转，从上到下？==》最终合成的位置由overlay过滤器设置，经确认是将裁剪的区域翻转后拼接到图像下半部分，
    //图像上半部分不变（不变是因为split分割出了两路流，过滤器是操作的辅助流）
    //配合使用crop：out_w=iw:out_h=ih/2:x=0:y=ih/2进行验证
    AVFilter *vflipFilter = avfilter_get_by_name("vflip");
    AVFilterContext *vflipFilter_ctx;
    ret = avfilter_graph_create_filter(&vflipFilter_ctx, vflipFilter, "vflip", NULL, NULL, filter_graph);
    if (ret < 0) {
        printf("Fail to create vflip filter\n");
        return -1;
    }

    //8. overlay filter：视频合成
    AVFilter *overlayFilter = avfilter_get_by_name("overlay");
    AVFilterContext *overlayFilter_ctx;
    ret = avfilter_graph_create_filter(&overlayFilter_ctx, overlayFilter, "overlay",
                                       "y=0:H/2", NULL, filter_graph);
    if (ret < 0) {
        printf("Fail to create overlay filter\n");
        return -1;
    }
    //  split用于分流
    //  crop确定裁剪位置
    //  vflip仅翻转图像
    //  overlay确定视频叠加位置

    //                          [main]
    //input ----> split ---------------------> overlay --> output
    //              |                             ^
    //              |[tmp]                  [flip]|
    //              |                             |
    //              v                             |
    //              +-----> crop --> vflip -------+

    //9.过滤器连接
    // src filter to split filter
    ret = avfilter_link(bufferSrc_ctx, 0, splitFilter_ctx, 0);
    if (ret != 0) {
        printf("Fail to link src filter and split filter\n");
        return -1;
    }
    // split filter's first pad to overlay filter's main pad
    ret = avfilter_link(splitFilter_ctx, 0, overlayFilter_ctx, 0);
    if (ret != 0) {
        printf("Fail to link split filter and overlay filter main pad\n");
        return -1;
    }
    // split filter's second pad to crop filter
    ret = avfilter_link(splitFilter_ctx, 1, cropFilter_ctx, 0);
    if (ret != 0) {
        printf("Fail to link split filter's second pad and crop filter\n");
        return -1;
    }
    // crop filter to vflip filter
    ret = avfilter_link(cropFilter_ctx, 0, vflipFilter_ctx, 0);
    if (ret != 0) {
        printf("Fail to link crop filter and vflip filter\n");
        return -1;
    }
    // vflip filter to overlay filter's second pad
    ret = avfilter_link(vflipFilter_ctx, 0, overlayFilter_ctx, 1);
    if (ret != 0) {
        printf("Fail to link vflip filter and overlay filter's second pad\n");
        return -1;
    }
    // overlay filter to sink filter
    ret = avfilter_link(overlayFilter_ctx, 0, bufferSink_ctx, 0);
    if (ret != 0) {
        printf("Fail to link overlay filter and sink filter\n");
        return -1;
    }

    //10. check filter graph
    ret = avfilter_graph_config(filter_graph, NULL);
    if (ret < 0) {
        printf("Fail in filter graph\n");
        return -1;
    }

    //11.打印filtergraph具体情况
    char *graph_str = avfilter_graph_dump(filter_graph, NULL);
    FILE* graphFile = NULL;
    fopen_s(&graphFile, "graphFile.txt", "w");  // 打印filtergraph的具体情况
    fprintf(graphFile, "%s", graph_str);
    av_free(graph_str);

    //数据处理，按帧处理
    AVFrame *frame_in = av_frame_alloc();
    unsigned char *frame_buffer_in = (unsigned char *)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_YUV420P, in_width, in_height, 1));
    av_image_fill_arrays(frame_in->data, frame_in->linesize, frame_buffer_in,
        AV_PIX_FMT_YUV420P, in_width, in_height, 1);

    AVFrame *frame_out = av_frame_alloc();
    unsigned char *frame_buffer_out = (unsigned char *)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_YUV420P, in_width, in_height, 1));
    av_image_fill_arrays(frame_out->data, frame_out->linesize, frame_buffer_out,
        AV_PIX_FMT_YUV420P, in_width, in_height, 1);

    frame_in->width = in_width;
    frame_in->height = in_height;
    frame_in->format = AV_PIX_FMT_YUV420P;
    uint32_t frame_count = 0;
    while (1) {
        // 读取yuv数据
        if (fread(frame_buffer_in, 1, in_width*in_height * 3 / 2, inFile) != in_width*in_height * 3 / 2) {
            break;
        }
        //input Y,U,V
        frame_in->data[0] = frame_buffer_in;
        frame_in->data[1] = frame_buffer_in + in_width*in_height;
        frame_in->data[2] = frame_buffer_in + in_width*in_height * 5 / 4;

        if (av_buffersrc_add_frame(bufferSrc_ctx, frame_in) < 0) {
            printf("Error while add frame.\n");
            break;
        }
        // filter内部自己处理
        /* pull filtered pictures from the filtergraph */
        ret = av_buffersink_get_frame(bufferSink_ctx, frame_out);
        if (ret < 0)
            break;

        //output Y,U,V,yuv分量的偏移要为行距的长度才行，实际写的长度为实际的宽，图像宽是4的倍数的话linesize和width是相等的
        if (frame_out->format == AV_PIX_FMT_YUV420P) {
            for (int i = 0; i < frame_out->height; i++) {
                fwrite(frame_out->data[0] + frame_out->linesize[0] * i, 1, frame_out->width, outFile);
            }
            for (int i = 0; i < frame_out->height / 2; i++) {
                fwrite(frame_out->data[1] + frame_out->linesize[1] * i, 1, frame_out->width / 2, outFile);
            }
            for (int i = 0; i < frame_out->height / 2; i++) {
                fwrite(frame_out->data[2] + frame_out->linesize[2] * i, 1, frame_out->width / 2, outFile);
            }
        }
        ++frame_count;
        if(frame_count % 25 == 0)
            printf("Process %d frame!\n",frame_count);
        av_frame_unref(frame_out);
    }

    fclose(inFile);
    fclose(outFile);

    av_frame_free(&frame_in);
    av_frame_free(&frame_out);
    avfilter_graph_free(&filter_graph); // 内部去释放AVFilterContext产生的内存

    printf("Exe Run Over\n");
    return 0;
}

效果图如下：