QT+ffmpeg实现视频解析的示例详解 QT+ffmpeg实现视频解析的示例详

一、创建QT项目
二、引入ffmpeg

1、复制头文件和lib
2、复制bin文件
3、简单测试

三、视频解析

1、创建线程
2、创建自定义绘制控件
3、使用自定义控件
4、开启线程，进行视频解析

一、创建QT项目首先安装了最新的Community版本，Creator是8.0.1版本了。

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然后进行项目的创建。

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得到的项目没有pro文件，而是CMakeLists.txt。

二、引入ffmpeg 从下面下载的ffmpeg-5.0.1-full_build-shared.7z。
https://www.gyan.dev/ffmpeg/builds/

1、复制头文件和lib
在项目内创建一个文件夹，我这里起名叫lib，然后在lib文件夹下创建了ffmpeg文件夹，然后将上面下载的压缩包内的include和lib文件夹复制到ffmpeg文件夹下。
然后修改CMakeLists.txt，添加如下的内容。

include_directories(${CMAKE_SOURCE_DIR}/lib/ffmpeg/include) target_link_libraries(QtFFmpegApp1 PRIVATE ${CMAKE_SOURCE_DIR}/lib/ffmpeg/lib/avcodec.lib${CMAKE_SOURCE_DIR}/lib/ffmpeg/lib/avdevice.lib${CMAKE_SOURCE_DIR}/lib/ffmpeg/lib/avfilter.lib${CMAKE_SOURCE_DIR}/lib/ffmpeg/lib/avformat.lib${CMAKE_SOURCE_DIR}/lib/ffmpeg/lib/avutil.lib${CMAKE_SOURCE_DIR}/lib/ffmpeg/lib/postproc.lib${CMAKE_SOURCE_DIR}/lib/ffmpeg/lib/swresample.lib${CMAKE_SOURCE_DIR}/lib/ffmpeg/lib/swscale.lib)

2、复制bin文件
将下面的dll文件复制到build-QtFFmpegApp1-Desktop_Qt_6_3_1_MinGW_64_bit-Debug文件夹下。

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3、简单测试
在mainwindow.h文件内添加以下引用

extern "C"{#include "libavformat/avformat.h"#include "libavformat/avio.h"#include "libavcodec/avcodec.h"#include "libavutil/buffer.h"#include "libavutil/error.h"#include "libavutil/mem.h"#include "libavutil/imgutils.h"#include #include #include }

在mainwindow.cpp文件内的MainWindow::MainWindow方法内添加

std::string s = avcodec_configuration(); QString dlgTitle = "information消息框"; QString strInfo = QString::fromStdString(s); QMessageBox::information(this, dlgTitle, strInfo, QMessageBox::Ok, QMessageBox::NoButton);

运行，会看到如下消息窗口，其中显示的ffmpeg的编译参数，看到这个就表明ffmpeg引入成功。

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三、视频解析
1、创建线程
（1）MyThread.h文件

#ifndef MYTHREAD_H#define MYTHREAD_H #include #include #include #include #include extern "C"{#include "libavformat/avformat.h"#include "libavformat/avio.h"#include "libavcodec/avcodec.h"#include "libavutil/buffer.h"#include "libavutil/error.h"#include "libavutil/mem.h"#include "libavutil/imgutils.h"#include #include #include } class MyThread : public QThread{Q_OBJECTpublic:MyThread(); protected:void run() override; signals:void minNumToamin(int min); void getPicFromFrame(QImage image); }; #endif // MYTHREAD_H

（2）MyThread.cpp文件

#include #include #define INBUF_SIZE 4096 MyThread::MyThread(){ } void MyThread::run(){const char* filename, * outfilename; const AVCodec* codec; AVCodecParserContext* parser; AVCodecContext* c = NULL; FILE* f; AVFrame* frame; AVFrame* pFrameBGR; uint8_t inbuf[INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE]; uint8_t* data; size_tdata_size; int ret; AVPacket* pkt; AVFormatContext* inFmtCtx = NULL; int video_in_stream_index = -1, audio_in_stream_index = -1; AVCodecID src_video_id = AVCodecID::AV_CODEC_ID_NONE, src_audio_id = AVCodecID::AV_CODEC_ID_NONE; SwsContext* sws_ctx; uint8_t* buffer = nullptr; //文件路径filename = "C:\\Users\\zyh\\Desktop\\2.mp4"; outfilename = ""; pkt = av_packet_alloc(); if (!pkt)exit(1); // 打开输入文件if ((ret = avformat_open_input(&inFmtCtx, filename, NULL, NULL)) < 0) {//LOGD("avformat_open_input() fail"); //releaseSources(); return; }if ((ret = avformat_find_stream_info(inFmtCtx, NULL)) < 0) {//LOGD("avformat_find_stream_info fail %d", ret); //releaseSources(); return; }// 输出输入文件信息av_dump_format(inFmtCtx, 0, filename, 0); for (int i = 0; i < inFmtCtx->nb_streams; i++) {AVCodecParameters* codecpar = inFmtCtx->streams[i]->codecpar; if (codecpar->codec_type == AVMEDIA_TYPE_VIDEO && video_in_stream_index == -1) {src_video_id = codecpar->codec_id; video_in_stream_index = i; }if (codecpar->codec_type == AVMEDIA_TYPE_AUDIO && audio_in_stream_index == -1) {src_audio_id = codecpar->codec_id; audio_in_stream_index = i; }} /* set end of buffer to 0 (this ensures that no overreading happens for damaged MPEG streams) */memset(inbuf + INBUF_SIZE, 0, AV_INPUT_BUFFER_PADDING_SIZE); /* find the MPEG-1 video decoder */codec = avcodec_find_decoder(src_video_id); if (!codec) {fprintf(stderr, "Codec not found\n"); exit(1); } parser = av_parser_init(codec->id); if (!parser) {fprintf(stderr, "parser not found\n"); exit(1); } c = avcodec_alloc_context3(codec); if (!c) {fprintf(stderr, "Could not allocate video codec context\n"); exit(1); } AVCodecParameters* codecpar = inFmtCtx->streams[video_in_stream_index]->codecpar; if ((ret = avcodec_parameters_to_context(c, codecpar)) < 0) {//LOGD("avcodec_parameters_to_context fail %d", ret); //releaseSources(); return; } /* For some codecs, such as msmpeg4 and mpeg4, width and heightMUST be initialized there because this information is notavailable in the bitstream. *//* open it */if (avcodec_open2(c, codec, NULL) < 0) {fprintf(stderr, "Could not open codec\n"); exit(1); } f = fopen(filename, "rb"); if (!f) {fprintf(stderr, "Could not open %s\n", filename); exit(1); } frame = av_frame_alloc(); pFrameBGR = av_frame_alloc(); if (!frame) {fprintf(stderr, "Could not allocate video frame\n"); exit(1); } int index = 0; while (av_read_frame(inFmtCtx, pkt) >= 0) { // 迭代结束后释放 av_read_frame 分配的 packet 内存//std::shared_ptr packetDeleter(&pkt, av_packet_unref); if(index >0) break; // 说明读取的视频数据if (pkt->stream_index == video_in_stream_index) {if ((ret = avcodec_send_packet(c, pkt)) < 0) {//LOGD("video avcodec_send_packet fail %s", av_err2str(ret)); //releaseSources(); return; }while (true) {// 从解码缓冲区接收解码后的数据if ((ret = avcodec_receive_frame(c, frame)) < 0) {if (ret == AVERROR_EOF) {exit(1); // 解码缓冲区结束了，那么也要flush编码缓冲区//doEncodeVideo(NULL); }break; } int numBytes = av_image_get_buffer_size(AV_PIX_FMT_RGB24, c->width, c->height, 1); if(buffer == nullptr) buffer = (uint8_t*)av_malloc(numBytes * sizeof(uint8_t)); av_image_fill_arrays(pFrameBGR->data, pFrameBGR->linesize, buffer, AV_PIX_FMT_RGB24,c->width, c->height, 1); sws_ctx = sws_getContext(codecpar->width, codecpar->height, (enum AVPixelFormat)codecpar->format,frame->width, frame->height, AV_PIX_FMT_RGB24, SWS_BICUBIC, NULL, NULL, NULL); sws_scale(sws_ctx, frame->data, frame->linesize, 0, c->height, pFrameBGR->data, pFrameBGR->linesize); // 图像转换sws_scale(sws_ctx, frame->data, frame->linesize, 0, c->height, pFrameBGR->data, pFrameBGR->linesize); // 得到QImageQImage tempImage((uchar*)pFrameBGR->data[0], c->width, c->height, QImage::Format_RGB888); // 对于qt还是不是很熟悉，理解是传递给主线程getPicFromFrame(tempImage); }} // 因为每一次读取的AVpacket的数据大小不一样，所以用完之后要释放av_packet_unref(pkt); } fclose(f); av_parser_close(parser); avcodec_free_context(&c); av_frame_free(&frame); av_packet_free(&pkt); }

2、创建自定义绘制控件
（1）PlayImage.h

#ifndef PLAYIMAGE_H#define PLAYIMAGE_H #include class PlayImage : public QWidget{Q_OBJECTpublic:explicit PlayImage(QWidget *parent = nullptr); void updateImage(const QImage& image); void updatePixmap(const QPixmap& pixmap); signals: protected:void paintEvent(QPaintEvent *event) override; private:QPixmap m_pixmap; }; #endif // PLAYIMAGE_H

（2）PlayImage.cpp

#include "playimage.h" #include PlayImage::PlayImage(QWidget *parent) : QWidget(parent){ } /** * @brief传入Qimage图片显示 * @param image */void PlayImage::updateImage(const QImage& image){updatePixmap(QPixmap::fromImage(image)); } /** * @brief传入QPixmap图片 * @param pixmap */void PlayImage::updatePixmap(const QPixmap &pixmap){m_pixmap = pixmap; update(); } /** * @brief使用Qpainter显示图片 * @param event */void PlayImage::paintEvent(QPaintEvent *event){if(!m_pixmap.isNull()){QPainter painter(this); #if 0// 经过粗略测试，QImage先缩放后转为QPixmap的方式在图像比较小时耗时少，图片越大耗时远大QPixmap pixmap = QPixmap::fromImage(m_image.scaled(this->size(), Qt::KeepAspectRatio)); // 先将QImage转换为QPixmap再进行缩放则耗时比较少，并且稳定，不会因为缩放图片大小而产生太大影响QPixmap pixmap1 = QPixmap::fromImage(m_image).scaled(this->size(), Qt::KeepAspectRatio); #endifQPixmap pixmap = m_pixmap.scaled(this->size(), Qt::KeepAspectRatio); int x = (this->width() - pixmap.width()) / 2; int y = (this->height() - pixmap.height()) / 2; painter.drawPixmap(x, y, pixmap); }QWidget::paintEvent(event); }

3、使用自定义控件
在mainwindow.ui的设计界面，拖一个Widget到主界面，然后在Widget上点击右键，然后选择提升为，在提升的类名称处输入上面自定义控件的类名。
如果选择下面的全局包含，就不用再单独包含头文件了。