Qt使用FFmpeg解码H.264视频流转成QImage

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使用简介：

在收到码流的时候调用H264::appendData方法将数据丢给H264实例去处理，处理完成后会触发信号imageData，在关联imageData信号的槽函数中将QImage刷新到界面上就可以了。

代码实现

头文件

#ifndef H264_H
#define H264_H

#include <QObject>
#include <QByteArray>
#include <QMutex>
#include <QByteArray>
#include <QThread>
#include <QImage>

extern "C"{
    #include <libavcodec/avcodec.h>
    #include <libavformat/avformat.h>
    #include <libswscale/swscale.h>
    #include <libavutil/imgutils.h>
}

class H264 : public QThread
{
    Q_OBJECT
public:
    explicit H264(QObject *parent = nullptr);
    bool init();
    bool genImageObj();
    void appendData(const QByteArray& data);
    void decode();
    void close() { m_isRun = false; wait(); }

private:
    AVPacket *m_avPacket;
    AVFrame *m_avFrameInput;
    AVFrame *m_avFramePicture;
    AVCodec *m_pCodec;
    AVCodecContext *m_avCodecCtx;
    AVCodecParserContext *m_pCodecParserCtx;
    SwsContext *m_pSwsContext;

    int m_nVideoWidth;
    int m_nVideoHeight;
    uint8_t *m_pPicBuffer;

    QByteArray m_buffer;
    QMutex m_mutex;
    bool m_isFirst;
    bool m_isRun;

signals:
    void imageData(QImage image);

protected:
    void run() override;


signals:

};

#endif // H264_H

源文件

#include "h264.h"
#include <QMutexLocker>
#include <QDebug>

H264::H264(QObject *parent)
    : QThread(parent)
    , m_isFirst(true)
{

}

bool H264::init()
{
    m_avPacket = av_packet_alloc();
    av_init_packet(m_avPacket);
    m_avFrameInput = av_frame_alloc();
    m_avFramePicture = av_frame_alloc();

    m_pCodec = (AVCodec*)avcodec_find_decoder(AVCodecID::AV_CODEC_ID_H264);
    if (!m_pCodec) return false;

    m_avCodecCtx = avcodec_alloc_context3(m_pCodec);
    if (!m_avCodecCtx) return false;

    m_pCodecParserCtx = av_parser_init(AVCodecID::AV_CODEC_ID_H264);
    if (!m_pCodecParserCtx) return false;

    if (avcodec_open2(m_avCodecCtx, m_pCodec, nullptr) < 0) {
        return false;
    }
    return true;
}

bool H264::genImageObj()
{
    AVPixelFormat srcFmt = AV_PIX_FMT_YUV420P;
    AVPixelFormat dstFmt = AV_PIX_FMT_RGB32;

    srcFmt = m_avCodecCtx->pix_fmt;

    int bytes = av_image_get_buffer_size(AV_PIX_FMT_RGB32, m_nVideoWidth, m_nVideoHeight, 1);
    m_pPicBuffer = (uint8_t*)av_malloc(bytes * sizeof(uint8_t));
    av_image_fill_arrays(m_avFramePicture->data, m_avFramePicture->linesize, m_pPicBuffer, dstFmt, m_nVideoWidth, m_nVideoHeight, 1);
    m_pSwsContext = sws_getContext(m_nVideoWidth, m_nVideoHeight, srcFmt, m_nVideoWidth, m_nVideoHeight, dstFmt, SWS_FAST_BILINEAR, nullptr, nullptr, nullptr);
    return true;
}

void H264::appendData(const QByteArray &data)
{
    QMutexLocker _(&m_mutex);
    m_buffer += data;
}

void H264::decode()
{
    QMutexLocker _(&m_mutex);

    while (m_buffer.size() > 0) {
        const int nBufferSize = m_buffer.size() + FF_BUG_NO_PADDING;
        QByteArray buf;
        buf.fill(0, nBufferSize);
        memcpy(buf.data(), m_buffer.constData(), m_buffer.size());

        int nLength = av_parser_parse2(
          m_pCodecParserCtx,
          m_avCodecCtx,
          &m_avPacket->data,
          &m_avPacket->size,
          (const uint8_t*)buf.constData(),
          m_buffer.size(),
          AV_NOPTS_VALUE, AV_NOPTS_VALUE, AV_NOPTS_VALUE);

        m_buffer.remove(0, nLength);

        if (m_avPacket->size == 0) {
            return;
        }

        switch (m_pCodecParserCtx->pict_type) {
        case AV_PICTURE_TYPE_I: break;
        case AV_PICTURE_TYPE_P: break;
        case AV_PICTURE_TYPE_B: break;
        default: break;
        }

        avcodec_send_packet(m_avCodecCtx, m_avPacket);
        int ret = avcodec_receive_frame(m_avCodecCtx, m_avFrameInput);
        if (ret < 0) return;
        if (m_isFirst) {
            m_nVideoWidth = m_avCodecCtx->width;
            m_nVideoHeight = m_avCodecCtx->height;
            genImageObj();
            m_isFirst = false;
        }
        sws_scale(m_pSwsContext, m_avFrameInput->data, m_avFrameInput->linesize, 0, m_nVideoHeight, m_avFramePicture->data, m_avFramePicture->linesize);
        QImage image(m_avFramePicture->data[0], m_nVideoWidth, m_nVideoHeight, QImage::Format_ARGB32);
        emit imageData(image);
    }
}

void H264::run()
{
    m_isRun = true;
    while (m_isRun) {
        decode();
    }
    av_packet_free(&m_avPacket);
    av_frame_free(&m_avFrameInput);
    av_frame_free(&m_avFramePicture);
    avcodec_free_context(&m_avCodecCtx);
}

使用

void Widget::onVideoFrame(QImage img){}

// 初始化h264解码
connect(&m_h264, &H264::imageData, this, &Widget::onVideoFrame);
m_h264.init();
m_h264.start();