User:Joger/Building Qt Multimedia with FFmpeg: Difference between revisions

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This page shows one example of how to build Qt Multimedia with the FFmpeg backend on Windows. Note that there are many ways to achieve the same result with Qt, but this is how I do it.
Building Qt Multimedia and FFmpeg from source are described in the Qt Documentation:


==Build setup assumed in this description==
* [https://doc-snapshots.qt.io/qt6-dev/qtmultimedia-building-ffmpeg.html Building FFmpeg from source].  
The commands in this description assumes that the build setup is like in the below list. If your setup is different, adjust the commands accordingly.
* [https://doc-snapshots.qt.io/qt6-dev/qtmultimedia-building-from-source.html Building Qt Multimedia from sources]
* OS: Windows 11 with dev drive mounted on D: (Using a dev drive makes builds faster when using Windows Defender antivirus)
* Qt source tree: D:\qt\qt6\
* Build directory containing all builds: D:\qt\build\
* Main (host) build for dev branch: D:\qt\build\dev\
* Visual Studio 2022 (MSVC)
* Have cmake in path
 
==Developer setup for Qt Multimedia on Windows==
 
=== Building FFmpeg ===
 
==== Option 1: Building FFmpeg on Windows using Qt's provisioning scripts ====
For building FFmpeg, Qt's own provisioning scripts can be very useful. These scripts are used in our CI infrastructure when building FFmpeg, but can also be used by developers
#Install 7-zip from provisioning: Run qt6\coin\provisioning\common\windows\install-sevenzip.ps1 as admin
#*Needed by provisioning script for FFmpeg to unzip downloaded FFmpeg
#Install msys2 from provisioning: Run qt6\coin\provisioning\common\windows\install-msys2.ps1 as admin
#*Needed by provisioning script for FFmpeg because FFmpeg requires tools from msys to configure
#If you want to enable '''debugging''' of FFmpeg, edit  qt6\coin\provisioning\common\shared\ffmpeg_config_options.txt
#*Replace <code enclose="none">--disable-debug</code> with <code enclose="none">--enable-debug --disable-optimizations</code>
#*<code enclose="none">--disable-optimizations&lt</code> will use MSVC <code enclose="none">/O1</code>, which still inlines functions and makes debugging hard.
#*Adding <code enclose="none">--optflags=-Og</code> reduces optimizations further, making debugging easier. With VS2022, this produces lots of warnings about using deprecated feature, but it works. Note that FFmpeg does not support compiling without any optimizations set <code enclose="none">-Od</code>.
#Install FFmpeg from provisioning: Run qt6\coin\provisioning\common\windows\install-ffmpeg.ps1 as admin
#*Since I only need MSVC build, I edit the install-ffmpeg.ps1 first, to comment out unnecessary versions
#*This  builds FFmpeg and sets FFMPEG_DIR=C:\FFmpeg-n6.0\build\msvc\installed\
 
====Option 2: Building FFmpeg on Windows using vcpkg====
If you don't already have vcpkg, install vcpkg:<blockquote>git clone <nowiki>https://github.com/microsoft/vcpkg</nowiki></blockquote>From within the new vcpkg directory, run<blockquote>bootstrap-vcpkg.bat</blockquote>Now, building FFmpeg is done by executing<blockquote>vcpkg install ffmpeg[core,swresample,swscale,avdevice]:x64-windows</blockquote>This will download all necessary dependencies and build FFmpeg into C:\dev\vcpkg\installed\x64-windows if vcpkg was cloned into C:\dev
 
'''Option 3: Building manually with MSYS2 (on Windows)'''
 
#Install MSYS2
#Start VS ''x64 Native Tools Command Prompt''
#Set environment variable MSYS2_PATH_TYPE to make MSYS2 inherit environment variable <code>set MSYS2_PATH_TYPE=inherit</code>
#First time, download necessary MSYS2 packages <code>pacman-key --init;pacman-key --populate msys2;pacman-key --refresh;pacman -S --noconfirm perl make yasm diffutils</code>
#Configure: <code>FFmpeg_install_dir/configure --prefix=installed --toolchain=msvc --disable-doc --enable-debug --enable-network --disable-lzma --enable-pic --disable-vulkan --disable-v4l2-m2m --disable-decoder=truemotion1 --enable-shared --disable-static --disable-optimizations --optflags=-Ob0</code>
# Install: <code>make install -j</code>
 
===Configure Qt main build===
I build Qt as stand-alone module to make builds run faster when working in QtMultimedia. But first, we need to build the necessary dependencies. I do this from command line with D:\qt\build\dev as current directory. Note that if you did build FFmpeg with vcpkg, you need to update the -DFFMPEG_DIR argument to point to the C:\dev\vcpkg\installed\x64-windows directory (not the bin-directory inside).<blockquote>..\..\qt6\configure.bat -debug -developer-build -init-submodules -submodules qtmultimedia -nomake tests -nomake examples -codereview-username johanseg -- -DFFMPEG_DIR=C:\FFmpeg-n6.0\build\msvc\installed --fresh & ninja</blockquote>I work almost exclusively using debug builds. If you need a release build, configure the release build in a separate build directory. This is a developer build, and we can use D:\qt\build\dev\qtbase\ as CMAKE_PREFIX_PATH when developing other Qt modules. By configuring this way, QtMultimedia is built, which is not strictly necessary since I develop QtMultimedia in a separate build tree, but it is an easy way to make sure all QtMultimedia dependencies are built.
 
===Configure Qt multimedia===
I configure QtMultimedia using a CMakeUserPresets.json file that is located in D:\qt\qt6\qtmultimedia instead of using a configure script. This way, I can open the D:\qt\qt6\qtmultimedia as a folder in Visual Studio and configure it from there.
 
The benefit of using CMakeUserPresets.json is that Visual Studio knows how to debug the tests and examples. I have not found a way that allows Visual Studio to use an existing CMakeCache as a starting point.
 
To make sure FFmpeg is deployed from the provisioning or vcpkg build into the Qt bin directory, make sure to specify the QT_DEPLOY_FFMPEG=ON CMake variable.
 
<code>
{
    "version": 5,
    "configurePresets": [
        {
            "name": "msvc",
            "hidden": true,
            "condition": {
                "type": "equals",
                "lhs": "${hostSystemName}",
                "rhs": "Windows"
            },
            "generator": "Ninja",
            "cacheVariables": {
                "CMAKE_CXX_COMPILER": "cl.exe",
                "CMAKE_C_COMPILER": "cl.exe"
            },
            "toolset": {
                "value": "v143,host=x64",
                "strategy": "external"
            },
            "architecture": {
                "value": "x64",
                "strategy": "external"
            }
        },
        {
            "name": "qtmultimedia",
            "inherits": "msvc",
            "cacheVariables": {
                "FEATURE_developer_build": true,
                "QT_BUILD_EXAMPLES": true,
                "QT_BUILD_EXAMPLES_BY_DEFAULT": false,
                "QT_BUILD_EXAMPLES_AS_EXTERNAL": false,
                "QT_BUILD_TESTS": true,
                "QT_BUILD_TESTS_BY_DEFAULT": false,
                "CMAKE_BUILD_TYPE": "Debug",
                "CMAKE_PREFIX_PATH": "D:/qt/build/dev/qtbase/",
                "QT_DEPLOY_FFMPEG": true,
                "FFMPEG_DIR": "C:/ffmpeg-n6.1.1/build/msvc/installed"
            },
            "environment": {
                "PATH": "D:/qt/build/dev/qtbase/bin;$penv{PATH}"
            }
        }
    ],
    "buildPresets": [
        {
            "name": "Build Qt Multimedia",
            "configurePreset": "qtmultimedia"
        }
    ]
}
</code>

Latest revision as of 16:02, 13 November 2024

Building Qt Multimedia and FFmpeg from source are described in the Qt Documentation:

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