Video Learning Notes (Day 2): Basic Environment Building (Mac version)

Install FFmpeg

1, install,

In a Mac environment, install FFmpeg directly using Homebrew.

brew install ffmpeg
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After the installation is complete, if you can view the FFmpeg version number on the command line, it indicates that the installation is successful.

ffmpeg -version
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2. Directory structure

You can viewFFmpegThe installation path

which ffmpeg
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Check the file

open /usr/local/bin
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Right click on theffmpeg, click on theAccording to the original body

You can jump toffmpegSpecific installation position

HomebrewThe installation of theFFmpegIt’s stored away/usr/local/Cellar/ffmpegThe installed version is4.3.2

bin: There are compiled executable programs: ffmpeg, ffplay, etc., which can be used directly on the command line, for example
- ffplay xx.mp4: You can play a video directly
- ffmpeg -version: You can view the FFmpeg version number
include: a header file that needs to be included during development
lib: library file to use when linking

Second, the QT

If you want to develop a player, must write interface, also in order to ensure cross-platform development, the GUI library used here isQt, the official developer tool QtCreator is cross-platform (Windows, Mac, Linux). Qt is developed using C++ programming language.
For this tutorial, select version 5.14.2 (paid versions starting with version 5.15),MacOS Big Sur version 11.1Above, you can install this packagehttps://d13lb3tujbc8s0.cloudfront.net/onlineinstallers/qt-unified-mac-x64-4.0.0-online.dmg, the choice of5.15Can be

1. Download from the official website

You can download the Mac installation package from the official website

Download and install step by step

2. Homebrew download

Qt is installed via Brew Install, and is finally installed on/usr/local/Cellar/qtDirectory.

brew install qt
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Install Qt Creator via Brew Install –cask, which is finally installed in the/usr/local/Caskroom/qt-creatorDirectory.

brew install --cask qt-creator
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3, configuration,

Qt installed via BREW is separate from Qt Creator. You need to set the Qt path in Qt Creator.
Open theQT Creator 的 preferences

findKits 的 Qt Versions, click on theadd

Qt’s path is in/usr/localIs hidden by default.
- You can use shortcut keysCommand + Shift + .Show hidden files and folders
- You can use shortcut keysCommand + Shift + GManually enter the Qt folder:/usr/local/Cellar/qt

You can seeqtThe folder

choosebinIn the directoryqmake

Then the configurationBuild a suite

Third, the development of

1. New projects

After you create the project, look as follows

Click on the building

Eliminate version warnings intest.proAdd to fileCONFIG+=sdk_no_version_check

2. Integrate FFmpeg into Qt project

Integration with FFmpeg requires modification of the. Pro file

INCLUDEPATH + # set header file path = / usr/local/Cellar/ffmpeg4.32./ include # Settings library file path LIBS + = L/usr/local/Cellar/ffmpeg4.32./lib \
        -lavcodec \
        -lavdevice \
        -lavfilter \
        -lavformat \
        -lavutil \
        -lpostproc \
        -lswscale \
        -lswresample \
        -lavresample
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Print FFmpeg version number in the program

#include "mainwindow.h"

#include <QDebug>

// Ffmpeg is a C library, so extern imports are required
extern "C" {
    #include <libavcodec/avcodec.h>
}

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    qDebug() < <av_version_info(a); }Copy the code

QTIt is cross-platform. If you need to import different paths on different platforms, you can also use the following methods

Paths can also be extracted and imported

Iv. Development basis

1. Basic use of controls

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    // Set the window title
    setWindowTitle("Main window");

    // Set the window size
    // Windows can be freely scaled by dragging edges
// resize(400, 400);

    // Set the window to a fixed size
    // Windows cannot freely shrink by dragging edges
    setFixedSize(400.400);

    // Set the window position
    // Use the upper-left corner of the parent control as the origin
    // If there is no parent control, use the upper-left corner of the screen as the origin
    move(100.100);
}
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2. Add child controls

#include <QPushButton>
 
// Create button
QPushButton *btn = new QPushButton;
// Set the text of the button
btn->setText("Login");
// Sets the parent control to the current window
btn->setParent(this);
// Set the position and size of the button
btn->move(50.50);
btn->resize(100.50);
 
// Create the second button
new QPushButton("Registered".this);
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C++ instance object

In many languages, instance objects created are stored inHeap memory areaIn the
C++, however, can be inThe stack areaStorage instance object

1) The heap stores instance objects

Use keywordsnewThe created instance object is stored in the heap

// Create a button in the heap
QPushButton *btn = new QPushButton;
// Set the text of the button
btn->setText("Login");
// Sets the parent control to the current window
btn->setParent(this);
// Set the position and size of the button
btn->move(50.50);
btn->resize(100.50);

// Create the second button
new QPushButton("Registered".this);
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2) Stack area stores instance objects

inmain.cppIn the file, the code is as follows

#include "mainwindow.h"

#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show(a);return a.exec(a); }Copy the code

One of theMainWindow w;This statement creates a stackMainWindowTypew
whenmainAt the end of the function,wBe released
QApplication a(argc, argv);This sentence is created in the stack areaQApplicationTypea
return a.exec();This sentence ismainThe return of the function,a.exec();Will callOperating cycleTo ensuremainThe function doesn’t end, sowWill never be released (will still be released after the program is closed)

3) Instance objects added to the main window cannot be created in the stack

There is no advanced memory management in C++ (such as reference counting in OC), which we created inThe stack areaCreate instance variables whenscopeWhen it’s over, they’ll be released

Instance variables created in the heap need to be released manually, but QT already does this for us. When the main window is released, it will automatically release all child controls added to the main window

Video Learning Notes (Day 2): Basic Environment Building (Mac version)

Install FFmpeg

1, install,

2. Directory structure

Second, the QT

1. Download from the official website

2. Homebrew download

3, configuration,

Third, the development of

1. New projects

2. Integrate FFmpeg into Qt project

Iv. Development basis

1. Basic use of controls

2. Add child controls

C++ instance object

1) The heap stores instance objects

2) Stack area stores instance objects

3) Instance objects added to the main window cannot be created in the stack

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