SRT: Upgrade libsrt from 1.4.1 to 1.5.1. v6.0.12 (#3362)

Co-authored-by: winlin <winlin@vip.126.com>

trunk/3rdparty/srt-1-fit/scripts/win-installer/README.md

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+# SRT Static Libraries Installer for Windows
+
+This directory contains scripts to build a binary installer for
+libsrt on Windows systems for Visual Studio applications using SRT.
+
+## SRT developer: Building the libsrt installer
+
+### Prerequisites
+
+These first two steps need to be executed once only.
+
+- Prerequisite 1: Install OpenSSL for Windows, both 64 and 32 bits.
+  This can be done automatically by running the PowerShell script `install-openssl.ps1`.
+
+- Prerequisite 2: Install NSIS, the NullSoft Installation Scripting system.
+  This can be done automatically by running the PowerShell script `install-nsis.ps1`.
+
+### Building the libsrt installer
+
+To build the libsrt installer, simply run the PowerShell script `build-win-installer.ps1`.
+Running it without parameters, for instance launching it from the Windows Explorer, is
+sufficient to build the installer.
+
+Optional parameters:
+
+- `-Version name` :
+  Use the specified string as version number for libsrt. By default, if the
+  current commit has a tag, use that tag (initial "v" removed, for instance
+  `1.4.3`). Otherwise, the defaut version is a detailed version number (most
+  recent version, number of commits since then, short commit SHA, for instance
+  `1.4.3-32-g22cc924`). Use that option if necessary to specify some other
+  non-standard form of version string.
+  
+- `-NoPause` :
+  Do not wait for the user to press `<enter>` at end of execution. By default,
+  execute a `pause` instruction at the end of execution, which is useful
+  when the script was launched from Windows Explorer. Use that option when the
+  script is invoked from another PowerShell script.
+
+The installer is then available in the directory `installers`.
+
+The name of the installer is `libsrt-VERS.exe` where `VERS` is the SRT version number
+(see the `-Version` option).
+
+The installer shall then be published as a release asset in the `srt` repository
+on GitHub, either as `libsrt-VERS.exe` or `libsrt-VERS-win-installer.zip`.
+In the latter case, the archive shall contain `libsrt-VERS.exe`.
+
+## SRT user: Using the libsrt installer
+
+### Installing the SRT libraries
+
+To install the SRT libraries, simply run the `libsrt-VERS.exe` installer which is
+available in the [SRT release area](https://github.com/Haivision/srt/releases).
+
+After installing the libsrt binaries, an environment variable named `LIBSRT` is
+defined with the installation root (typically `C:\Program Files (x86)\libsrt`).
+
+If there is a need for automation, in a CI/CD pipeline for instance, the download
+of the latest `libsrt-VERS.exe` and its installation can be automated using the
+sample PowerShell script `install-libsrt.ps1` which is available in this directory.
+This script may be freely copied in the user's build environment.
+
+When run without parameters (for instance from the Windows explorer), this
+script downloads and installs the latest version of libsrt.
+
+Optional parameters:
+
+- `-Destination path` :
+  Specify a local directory where the libsrt package will be downloaded.
+  By default, use the `tmp` subdirectory from this script's directory.
+
+- `-ForceDownload` :
+  Force a download even if the package is already downloaded in the
+  destination path. Note that the latest version is always checked.
+  If a older package is already present but a newer one is available
+  online, the newer one is always downloaded, even without this option.
+
+- `-GitHubActions` :
+  When used in a GitHub Actions workflow, make sure that the `LIBSRT`
+  environment variable is propagated to subsequent jobs. In your GitHub
+  workflow, in the initial setup phase, use 
+  `script-dir\install-libsrt.ps1 -GitHubActions -NoPause`.
+
+- `-NoInstall` :
+  Do not install the package, only download it. By default, libsrt is installed.
+
+- `-NoPause` :
+  Do not wait for the user to press `<enter>` at end of execution. By default,
+  execute a `pause` instruction at the end of execution, which is useful
+  when the script was launched from Windows Explorer. Use that option when the
+  script is invoked from another PowerShell script.
+
+### Building Windows applications with libsrt
+
+In the SRT installation root directory (specified in environment variable `LIBSRT`),
+there is a Visual Studio property file named `libsrt.props`. Simply reference this
+property file in your Visual Studio project to use libsrt.
+
+You can also do that manually by editing the application project file (the XML
+file named with a `.vcxproj` extension). Add the following line just before
+the end of the file:
+
+~~~
+<Import Project="$(LIBSRT)\libsrt.props"/>
+~~~
+
+With this setup, just compile your application normally, either using the
+Visual Studio IDE or the MSBuild command line tool.
+
+## Files reference
+
+This directory contains the following files:
+
+| File name               | Usage
+| ----------------------- | -----
+| build-win-installer.ps1 | PowerShell script to build the libsrt installer.
+| install-libsrt.ps1      | Sample PowerShell script to automatically install libsrt (for user's projects).
+| install-openssl.ps1     | PowerShell script to install OpenSSL (prerequisite to build the installer).
+| install-nsis.ps1        | PowerShell script to install NSIS (prerequisite to build the installer).
+| libsrt.nsi              | NSIS installation script (used to build the installer).
+| libsrt.props            | Visual Studio property files to use libsrt (embedded in the installer).
+| README.md               | This text file.