如何在Qt4中播放YUV视频？

Question

我想使用Qt播放YUV视频序列。 现在我通过在QPixmap上逐像素使用DrawPixel来使用QPixmap。 但是，它不能实时播放视频。 如何提高速度？

Answer 1

您是否尝试过使用VideoPlayer之类的Phonon类？

看看这个：

http://doc.qt.io/archives/4.6/phonon-videoplayer.html

Answer 2

逐像素是创建图片的最慢方法。 这将提高性能很多 ，如果你之前处理的图像数据和使用的QPixmap的loadFromData（）方法。

Answer 3

好吧，DrawPixel绝对是性能最差的解决方案。

如今， QOpenGLWiget（Qt 5）可用于将视频帧渲染为纹理。 实际上，取决于视频像素格式，它可以是简单的纹理渲染，也可以是通过着色器并进一步绘制纹理的像素格式转换。

这个问题很老，所以我留下一个粗略的解决方案，只是因为我自己花了一些时间才能解决这个问题。 因此，最简单的方法（不是最佳方法，因为可以进行很多优化）是：

OpenGLDisplayRGB.h

#pragma once


#include <QOpenGLWidget>
#include <QOpenGLFunctions>
#include <QScopedPointer>
#include <QException>


/*!
 * \brief The OpenGLDisplay class
 * Simple OpenGL display, that renders RGBA to texture
 */
class OpenGLDisplayRGB : public QOpenGLWidget, public QOpenGLFunctions
{
    Q_OBJECT


public:
    explicit OpenGLDisplayRGB(QWidget* parent = nullptr);
    ~OpenGLDisplayRGB() override;


protected:
    void initializeGL() override;
    void resizeGL(int w, int h) override;
    void paintGL() override;

    void closeEvent(QCloseEvent* e) override;


public:
    void DisplayVideoFrame(unsigned char* data, int frameWidth, int frameHeight);


    Q_SIGNAL void closed();



private:
    struct OpenGLDisplayRGBImpl;
    QScopedPointer<OpenGLDisplayRGBImpl> impl;
};

OpenGLDisplayRGB.cpp

#include "OpenGLDisplayRGB.h"

#include <QOpenGLShader>
#include <QOpenGLTexture>
#include <QCoreApplication>
#include <QResizeEvent>
#include <QTimer>
#include <QDebug>


#define ATTRIB_VERTEX 0
#define ATTRIB_TEXTURE 1

namespace
{
    //Vertex matrix
    static const GLfloat vertexVertices[] = {
        -1.0f, -1.0f,
         1.0f, -1.0f,
         -1.0f, 1.0f,
         1.0f, 1.0f,
    };

    //Texture matrix
    static const GLfloat textureVertices[] = {
        0.0f,  1.0f,
        1.0f,  1.0f,
        0.0f,  0.0f,
        1.0f,  0.0f,
    };
}

struct OpenGLDisplayRGB::OpenGLDisplayRGBImpl
{
    OpenGLDisplayRGBImpl(QObject* ownerPtr)
        : mBufRGB(nullptr)
        //, mRepaintTimer(new QTimer(ownerPtr))
        , mEnabled(true)
        , mShaderProgram(new QOpenGLShaderProgram(ownerPtr))
        , mTexture(new QOpenGLTexture(QOpenGLTexture::Target2D))
    { }

    unsigned char*                      mBufRGB;
    //QTimer*                             mRepaintTimer;
    bool                                mEnabled;

    QOpenGLShader*                      mVShader;
    QOpenGLShader*                      mFShader;
    QOpenGLShaderProgram*               mShaderProgram;

    QScopedPointer<QOpenGLTexture>      mTexture;

    int                                 mTextureUniform;
    GLsizei                             mVideoW, mVideoH;

};

/*************************************************************************/

OpenGLDisplayRGB::OpenGLDisplayRGB(QWidget* parent)
    : QOpenGLWidget(parent)
    , impl(new OpenGLDisplayRGBImpl(this))
{
    setAttribute(Qt::WA_OpaquePaintEvent);
//    setAttribute(Qt::WA_PaintOnScreen);
    setAttribute(Qt::WA_NoSystemBackground);

    /*
    impl->mRepaintTimer->setInterval(50);
    connect(impl->mRepaintTimer, SIGNAL(timeout()), this, SLOT(update()));
    impl->mRepaintTimer->start();*/
}


OpenGLDisplayRGB::~OpenGLDisplayRGB()
{
    makeCurrent();
}


void OpenGLDisplayRGB::DisplayVideoFrame(unsigned char *data, int frameWidth, int frameHeight)
{
    impl->mVideoW = frameWidth;
    impl->mVideoH = frameHeight;
    impl->mBufRGB = data;
    update();
}


void OpenGLDisplayRGB::initializeGL()
{
    initializeOpenGLFunctions();

    glEnable(GL_DEPTH_TEST);

    /* Modern opengl rendering pipeline relies on shaders to handle incoming data.
     *  Shader: is a small function written in OpenGL Shading Language (GLSL).
     * GLSL is the language that makes up all OpenGL shaders.
     * The syntax of the specific GLSL language requires the reader to find relevant information. */

    impl->mEnabled = impl->mShaderProgram->addShaderFromSourceFile(QOpenGLShader::Vertex, ":/OpenGL/simple_vertex_shader.v.glsl");
    if(!impl->mEnabled)
        qDebug() << QString("[Error] Vertex shader failed: %1").arg(impl->mShaderProgram->log());

    impl->mShaderProgram->addShaderFromSourceFile(QOpenGLShader::Fragment, ":/OpenGL/simple_texture_shader.f.glsl");
    if(!impl->mEnabled)
        qDebug() << QString("[Error] Fragment shader failed: %1").arg(impl->mShaderProgram->log());

    // Bind the property vertexIn to the specified location ATTRIB_VERTEX, this property
    // has a declaration in the vertex shader source
    impl->mShaderProgram->bindAttributeLocation("vertexIn", ATTRIB_VERTEX);
    // Bind the attribute textureIn to the specified location ATTRIB_TEXTURE, the attribute
    // has a declaration in the vertex shader source
    impl->mShaderProgram->bindAttributeLocation("textureIn", ATTRIB_TEXTURE);
    //Link all the shader programs added to
    impl->mShaderProgram->link();
    //activate all links
    impl->mShaderProgram->bind();
    // Read the position of the data variable tex_rgb in the shader, the declaration
    // of these variables can be seen in
    // fragment shader source
    impl->mTextureUniform = impl->mShaderProgram->uniformLocation("uSampler");

    // Set the value of the vertex matrix of the attribute ATTRIB_VERTEX and format
    glVertexAttribPointer(ATTRIB_VERTEX, 2, GL_FLOAT, 0, 0, vertexVertices);
    // Set the texture matrix value and format of the attribute ATTRIB_TEXTURE
    glVertexAttribPointer(ATTRIB_TEXTURE, 2, GL_FLOAT, 0, 0, textureVertices);
    // Enable the ATTRIB_VERTEX attribute data, the default is off
    glEnableVertexAttribArray(ATTRIB_VERTEX);
    // Enable the ATTRIB_TEXTURE attribute data, the default is off
    glEnableVertexAttribArray(ATTRIB_TEXTURE);

    impl->mTexture->create();

    impl->mTexture->setMinMagFilters(QOpenGLTexture::Linear, QOpenGLTexture::Linear);
    impl->mTexture->setWrapMode(QOpenGLTexture::ClampToEdge);

    glClearColor (1.0f, 0.0f, 1.0f, 1.0f); // set the background color
}

void OpenGLDisplayRGB::resizeGL(int w, int h)
{
    if(h == 0)// prevents being divided by zero
        h = 1;// set the height to 1

    // Set the viewport
    glViewport(0, 0, w, h);
}

void OpenGLDisplayRGB::paintGL()
{
    if (!impl->mEnabled || !impl->mBufRGB)
        return; //RET

    // Load y data texture
    // Activate the texture unit GL_TEXTURE0
    glActiveTexture(GL_TEXTURE0);
    // Use the texture generated from y to generate texture
    glBindTexture(GL_TEXTURE_2D, impl->mTexture->textureId());

    // Use the memory mBufYuv data to create a real y data texture
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, impl->mVideoW, impl->mVideoH, 0, GL_RGBA, GL_UNSIGNED_BYTE, impl->mBufRGB);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

    // Specify y texture to use the new value can only use 0, 1, 2, etc. to represent
    // the index of the texture unit, this is the place where opengl is not humanized
    //0 corresponds to the texture unit GL_TEXTURE0 1 corresponds to the
    // texture unit GL_TEXTURE1 2 corresponds to the texture unit GL_TEXTURE2
    glUniform1i(impl->mTextureUniform, 0);
    // Use the vertex array way to draw graphics
    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
}


void OpenGLDisplayRGB::closeEvent(QCloseEvent *e)
{
    emit closed();
    e->accept();
}

simple_texture_shader.f.glsl

varying vec2 vTextureCoord;
uniform sampler2D uSampler;

void main(void)
{
    gl_FragColor = texture2D(uSampler, vTextureCoord);
}

simple_vertex_shader.v.glsl

attribute vec4 vertexIn;
attribute vec2 textureIn;
varying vec2 vTextureCoord;

void main(void)
{
    gl_Position = vertexIn;
    vTextureCoord = textureIn;
}