Qt +ffmpeg(vp8) 记录视频每一帧并生成webm文件格式

   WebM由Google提出，是一个开放、免费的媒体文件格式。其中Google将其拥有的VP8视频编码技术以类似BSD授权开源。WebM VP8实现了完全的免费开源与授权开放，并且，经过Google持续性的技术优化，其解码速度与开发工具显著增强，在压缩效率和性能方面的表现较发布初期显著提升。在Qt中的具体实现方法是继承QAbstractVideoSurface，然后在类Encoding中创建编码线程，最终通过信号与槽来进行数据传递。ffmpeg库自己网上搜索下载，内部包含有vp8编解码器。以下代码能实现vp8的初始化配置以及视频编码的具体过程。整个工程需要的私信我~

具体代码------cameravideosurface.h文件
#include <QAbstractVideoSurface>
#include <QTemporaryFile>
#include <QThread>
#include <QDebug>
#include <QTime>#define BIT_RATE 8000000
#define PTS_TIMES 40                     //Video of 25fps looks better in VLC, 25fps=40msextern "C"                               //FFmpeg libary
{
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>
#include <libavdevice/avdevice.h>
#include <libavutil/avutil.h>
#include "libavutil/imgutils.h"
#include "libavutil/opt.h"
}class Encoding : public QObject
{Q_OBJECTpublic :Encoding(AVFormatContext *p_AVFormatContext, AVCodecContext *p_AVCodecContext, AVFrame *p_AVFrame, AVPacket *p_AVPacket, struct SwsContext *p_image_convert_ctx);~Encoding();public slots:void slot_encodeImage(QImage m_image, bool m_isFileClosed);private:AVFormatContext *m_AVFormatContext =  nullptr;AVCodecContext *m_AVCodecContext = nullptr;AVFrame *m_AVFrame = nullptr;AVPacket *m_AVPacket = nullptr;struct SwsContext *image_convert_ctx = nullptr;int frame_index = 0;
};class CameraVideoSurface : public QAbstractVideoSurface
{Q_OBJECTpublic:CameraVideoSurface(int width = 1280, int heigth = 720, int frameRate = 30, bool image_reverse = false);~CameraVideoSurface();void fileFinished(QString correctFileName = "No_name");bool present(const QVideoFrame &frame);QList<QVideoFrame::PixelFormat> supportedPixelFormats(QAbstractVideoBuffer::HandleType type = QAbstractVideoBuffer::NoHandle) const;void TriggerSignalTrue();signals:void signal_showFrame(QImage image);void signal_encodeImage(QImage m_image, bool isFileClosed = false);private:QImage m_image;AVFormatContext *m_AVFormatContext;AVStream *m_AVStream;AVCodec *m_AVCodec;AVCodecContext *m_AVCodecContext;AVFrame *m_AVFrame;AVPacket *m_AVPacket;QTemporaryFile *pTempFile;struct SwsContext *image_convert_ctx = nullptr;bool m_triggerSignal = false;bool isFileClosed = false;int ret = 0;bool m_image_reverse = false;Encoding *m_encoding = nullptr;QThread workerThread;
};

具体代码------cameravideosurface.cpp文件
CameraVideoSurface::CameraVideoSurface(int width, int height, int frameRate, bool image_reverse) : QAbstractVideoSurface()
{av_register_all();                                                  //Register all codecs in FFmpegm_image_reverse = image_reverse;pTempFile = new QTemporaryFile;pTempFile->open();QString outputFile = pTempFile->fileName();ret =  avformat_alloc_output_context2(&m_AVFormatContext, nullptr, "webm", outputFile.toLocal8Bit().data());  //Allocate an AVFormatContext for Webm.if (ret != 0)return;m_AVCodec = avcodec_find_encoder(AV_CODEC_ID_VP8);                  //Find VP8 encoderif(m_AVCodec == nullptr)return;m_AVCodecContext = avcodec_alloc_context3(m_AVCodec);               //Allocate an AVCodecContext for VP8if(m_AVCodecContext == nullptr)return;m_AVCodecContext->bit_rate = BIT_RATE;                              //Encoding bitrate, affect the clarity of videom_AVCodecContext->width = width;                                    //frame width, height set by outsidem_AVCodecContext->height = height;m_AVCodecContext->frame_number = 1;                                 //do not changem_AVCodecContext->time_base.num = 1;                                //do not changem_AVCodecContext->time_base.den = frameRate;                        //set by outside(in seconds), internal timebasem_AVCodecContext->gop_size = 0;                                     //Group of picture, Interval between two I_frames, do not change otherwise you can not seek frame correctly.m_AVCodecContext->pix_fmt = AV_PIX_FMT_YUV420P;                     //do not changem_AVCodecContext->max_b_frames = 0;                                 //Set B_frame = 0, do not changeif (m_AVFormatContext->oformat->flags & AVFMT_GLOBALHEADER)         //Some formats want stream headers to be separated.m_AVCodecContext->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;av_opt_set(m_AVCodecContext->priv_data, "quality", "realtime", 0);  //VP8 must be setAVDictionary *param = nullptr;if(avcodec_open2(m_AVCodecContext, m_AVCodec, &param) < 0)          //Open encoderreturn;m_AVStream = avformat_new_stream(m_AVFormatContext, m_AVCodec);     //Create output streamif (m_AVStream == nullptr)return;m_AVStream->time_base = m_AVCodecContext->time_base;                // 1/frameRate  eg: 30frames per secondsm_AVStream->codec = m_AVCodecContext;if(avio_open(&m_AVFormatContext->pb, outputFile.toStdString().c_str(), AVIO_FLAG_READ_WRITE) < 0 )      //Open output filereturn;if(avformat_write_header(m_AVFormatContext, nullptr) < 0)           //Write header of package formatreturn;m_AVFrame = av_frame_alloc();m_AVFrame->width  = m_AVCodecContext->width;m_AVFrame->height = m_AVCodecContext->height;m_AVFrame->format = m_AVCodecContext->pix_fmt;m_AVFrame->pts = 0;m_AVFrame->format = AV_PIX_FMT_YUV420P;av_image_alloc(m_AVFrame->data, m_AVFrame->linesize, m_AVFrame->width, m_AVFrame->height, m_AVCodecContext->pix_fmt, 32);image_convert_ctx = sws_getContext(m_AVCodecContext->width, m_AVCodecContext->height, AV_PIX_FMT_RGB32,  //Data source of input imagem_AVCodecContext->width, m_AVCodecContext->height, AV_PIX_FMT_YUV420P, SWS_BICUBIC, nullptr, nullptr, nullptr);   //Data source of output imageif(image_convert_ctx == nullptr)return;m_AVPacket = av_packet_alloc();av_init_packet(m_AVPacket);if( m_encoding != nullptr ){delete m_encoding;m_encoding = nullptr;}m_encoding = new Encoding(m_AVFormatContext, m_AVCodecContext, m_AVFrame, m_AVPacket, image_convert_ctx);m_encoding->moveToThread(&workerThread);connect(this, SIGNAL(signal_encodeImage(QImage, bool)), m_encoding, SLOT(slot_encodeImage(QImage, bool)));workerThread.start();
}QList<QVideoFrame::PixelFormat>CameraVideoSurface::supportedPixelFormats(QAbstractVideoBuffer::HandleType type) const
{Q_UNUSED(type);QList<QVideoFrame::PixelFormat> pixelFormats;pixelFormats<<QVideoFrame::Format_RGB32;                //Add two pixel formats which I usepixelFormats<<QVideoFrame::Format_YUV420P;return pixelFormats;
}bool CameraVideoSurface::present(const QVideoFrame &frame)  //Execute when camera gets one frame. If you set cameraRate 30fps, present() will be executed every 33.33ms
{if(frame.isValid())                                     //Identifies whether a video frame is valid.{QVideoFrame cloneFrame(frame);cloneFrame.map(QAbstractVideoBuffer::ReadOnly);     //Map the frame to memoryQImage m_image(cloneFrame.bits(), cloneFrame.width(), cloneFrame.height(), QVideoFrame::imageFormatFromPixelFormat(frame.pixelFormat()));  //Form a picturem_image = m_image.mirrored(m_image_reverse, true);  //horizontal, verticalif( m_triggerSignal )          //Get the trigger signal from outside or timer{emit signal_encodeImage(m_image, isFileClosed);m_triggerSignal = false;}emit signal_showFrame(m_image);cloneFrame.unmap();return true;}elsereturn false;
}void CameraVideoSurface::fileFinished(QString correctFileName)  //QString correctFileName
{av_write_trailer(m_AVFormatContext);         //Write tail of package formatavio_closep(&m_AVFormatContext->pb);         //Close and free avio_open()if(pTempFile->open()){pTempFile->copy(correctFileName);        //Copy pTempFile's content to the file named correctFileNamedelete pTempFile;pTempFile = nullptr;}isFileClosed = true;                         //File state flag must be set
}CameraVideoSurface::~CameraVideoSurface()
{if(m_encoding != nullptr){workerThread.exit(0);delete m_encoding;m_encoding = nullptr;}avformat_close_input(&m_AVFormatContext);av_frame_free(&m_AVFrame);
}void CameraVideoSurface::TriggerSignalTrue()      //single trigger
{m_triggerSignal = true;
}Encoding::Encoding(AVFormatContext *p_AVFormatContext, AVCodecContext *p_AVCodecContext, AVFrame *p_AVFrame, AVPacket *p_AVPacket, struct SwsContext *p_image_convert_ctx)
{m_AVFormatContext = p_AVFormatContext;m_AVCodecContext = p_AVCodecContext;m_AVFrame = p_AVFrame;m_AVPacket = p_AVPacket;image_convert_ctx = p_image_convert_ctx;
}Encoding::~Encoding()
{m_AVFormatContext = nullptr;m_AVCodecContext = nullptr;m_AVFrame = nullptr;m_AVPacket = nullptr;image_convert_ctx = nullptr;
}void Encoding::slot_encodeImage(QImage m_image, bool isFileClosed)
{const uint8_t *data[AV_NUM_DATA_POINTERS] = {nullptr};data[0] = m_image.constBits();                  //Get image raw dataint linesize[AV_NUM_DATA_POINTERS] = {0};linesize[0] = m_AVCodecContext->width * 4;      //RGB32 occupies 4 bytes, do not changesws_scale(image_convert_ctx, data, linesize, 0, m_AVCodecContext->height, m_AVFrame->data, m_AVFrame->linesize);  //Do not changeframe_index++;m_AVFrame->pts = frame_index * PTS_TIMES;       //Set ptsm_AVPacket->data = nullptr;m_AVPacket->size = 0;QTime timer;timer.start();int ret = avcodec_send_frame(m_AVCodecContext, m_AVFrame);  //codec context, m_AVFrame contains the raw video frame. Supply a raw video frame to the encoder.qDebug() << "Time 1 duration: " << timer.elapsed();QTime m_timer;m_timer.start();while(ret == 0){ret = avcodec_receive_packet(m_AVCodecContext, m_AVPacket);  //codec context, m_AVPacket is the packet buffer of encoder. Read encoded data from the encoder.if( ret == AVERROR(EAGAIN) )break;else if( ret < 0 )break;if( !isFileClosed )        //If the output file has been closed, the last packet can not write into file and errorav_interleaved_write_frame(m_AVFormatContext, m_AVPacket);     //Write a packet to an output fileav_packet_unref(m_AVPacket);       //Wipe the packet}qDebug() << "Time 2 duration: " << m_timer.elapsed();
}

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