Introduction

Secure Reliable Transport (SRT) is a proprietary transport technology that optimizes streaming performance across unpredictable networks, such as the Internet.

Secure	Encrypts video streams
Reliable	Recovers from severe packet loss
Transport	Dynamically adapts to changing network conditions

SRT is applied to contribution and distribution endpoints as part of a video stream workflow to deliver the best quality and lowest latency video at all times.

As audio/video packets are streamed from a source to a destination device, SRT detects and adapts to the real-time network conditions between the two endpoints. SRT helps compensate for jitter and bandwidth fluctuations due to congestion over noisy networks, such as the Internet. Its error recovery mechanism minimizes the packet loss typical of Internet connections. And SRT supports AES encryption for end-to-end security, keeping your streams safe from prying eyes.

Join the conversation in the #development channel on Slack.

Guides

• Why SRT Was Created
• Using the stransmit App
• SRT Encryption

Requirements

• cmake (as build system)
• OpenSSL
• Pthreads (for POSIX systems it's builtin, for Windows there's a library)

For Linux:

Install cmake and openssl-devel (or similar name) package. For pthreads there should be -lpthreads linker flag added.

Ubuntu 14

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install tclsh pkg-config cmake libssl-dev build-essential
./configure
make

CentOS 7

sudo yum update
sudo yum install tcl pkgconfig openssl-devel cmake gcc gcc-c++ make automake
./configure
make

CentOS 6

sudo yum update
sudo yum install tcl pkgconfig openssl-devel cmake gcc gcc-c++ make automake
sudo yum install centos-release-scl-rh devtoolset-3-gcc devtoolset-3-gcc-c++
scl enable devtoolset-3 bash
./configure --use-static-libstdc++ --with-compiler-prefix=/opt/rh/devtoolset-3/root/usr/bin/
make

For Mac (Darwin, iOS):

Install cmake and openssl with development files from "brew". Note that the system version of OpenSSL is inappropriate, although you should be able to use any newer version compiled from sources, if you prefer.

brew install cmake
brew install openssl
export OPENSSL_ROOT_DIR=$(brew --prefix openssl)
export OPENSSL_LIB_DIR=$(brew --prefix openssl)"/lib"
export OPENSSL_INCLUDE_DIR=$(brew --prefix openssl)"/include"
./configure
make

For Windows:

1. Please download and install OpenSSL for Windows.

The 64-bit devel package can be downloaded from here:

 http://slproweb.com/download/Win64OpenSSL-1_0_2a.exe

(Note that the last letter or version number may be changed and older versions no longer available. If this isn't found, check here: http://slproweb.com/products/Win32OpenSSL.html )

It's expected to be installed in C:\OpenSSL-Win64 (see the above variables).

Note that this version is compiled most likely for Visual Studio 2013. For other versions you better download and compile the sources by yourself, from: https://github.com/openssl/openssl

The instruction for Windows: http://developer.covenanteyes.com/building-openssl-for-visual-studio/

2. Compile and install Pthreads for Windows from this submodule:

   submodules/pthread-win32

Please follow the steps:

a. Using Visual Studio 2013, please open this file:

 pthread_lib.2013.vcxproj

b. Make sure to select configuration: Release and x64.

c. Make sure that the pthread_lib project will be built.

d. After building, find the pthread_lib.lib file (directory is probably: bin\x64_MSVC2013.Release). Copy this file to C:\pthread-win32\lib (or whatever other location you configured in variables).

e. Copy include files to C:\pthread-win32\include - the following ones:

 pthread.h
 sched.h
 semaphore.h

(They are in the toplevel directory, there are actually no meaningful subdirs here) (NOTE: the win32 is part of the project name. It will become 32 or 64 depending on selection)

3. Install cmake for Windows. The CMake GUI will help you configure the project.

It will try to find OpenSSL and pthreads. If you installed them in the default location, they will be found automatically. If not, you can define the following variables to help CMake find them:

OPENSSL_ROOT_DIR=<path to OpenSSL instalation>
OPENSSL_LIBRARIES=<path to all the openssl libraries to link>
OPENSSL_INCLUDE_DIR=<path to the OpenSSL include dir>

PTHREAD_INCLUDE_DIR=<path to where pthread.h lies>
PTHREAD_LIBRARY=<path to pthread.lib>

4. For the sake of cmake generation: When you want to have a 64-bit version, remember that cmake by some reason adds /machine:X86 to the linker options. There are about four variables ended with _LINKER_FLAGS in the CMakeCache.txt file (also available with Advanced checked in CMake GUI). Remove them, or change into /machine:X64.

Also, just after you generated the project for MSVC (if you fail or forget to do that before the first compiling, you'll have to delete and regenerate all project files) then open Configuration Manager exactly after generation from cmake and setup x86 platform with requesting to generate this for every subproject.

5. IMPORTANT FOR DEVELOPERS AND CONTRIBUTORS: If you make any changes that fix something in the Windows version, remember to keep the project working also for all other platforms. To simplify the verification if you just would like to do it on the Windows machine, please install Cygwin and make another build for Cygwin, for example (remember that 'configure' script requires tcl8.5 package):

    mkdir build-cygwin
    cd build-cygwin
    ../configure --prefix=install --cygwin-use-posix
    make
   

The Cygwin platform isn't any important target platform for this project, but it's very useful to check if the project wouldn't be build-broken on Linux.