realsense-hello.cpp:7:1: error: ‘p’ does not name a type
 p.start();
realsense-hello.cpp:23:6: error: ‘cout’ in namespace ‘std’ does not name a type
 std::cout << "The camera is facing an object " << dist_to_center << " meters away \r";
I would like to make it work before starting developping my own code.
This is the code I try to compile :
realsense-hello.cpp
#include <librealsense2/rs.hpp> // Include Intel RealSense Cross Platform API
// Create a Pipeline - this serves as a top-level API for streaming and processing frames
rs2::pipeline p;
// Configure and start the pipeline
p.start();
// Block program until frames arrive
rs2::frameset frames = p.wait_for_frames();
// Try to get a frame of a depth image
rs2::depth_frame depth = frames.get_depth_frame();
// Get the depth frame's dimensions
float width = depth.get_width();
float height = depth.get_height();
// Query the distance from the camera to the object in the center of the image
float dist_to_center = depth.get_distance(width / 2, height / 2);
// Print the distance
std::cout << "The camera is facing an object " << dist_to_center << " meters away \r";
How can I make it work ? Let me know if I should update something or add anything,
Thanks in advance for your help.
          
Hi @remilamoureuxlevesque  The SDK example programs use a different build method from the typical approach that would be used to create your own program, so they are not the best tutorial for learning how to set up an independent project and create the linkages to the librealsense library files.  The building of rs-hello-realsense is discussed at #6797
Basically, the SDK examples are built together in a bundle of programs when first installed instead of being built individually.  After one of the programs is modified by a RealSense user, running 'make' again will only rebuild the programs that have been modified and not all of the examples.
Intel provide a simple Getting Started project template at the link below.
https://github.com/zivsha/librealsense/tree/getting_started_example/examples/getting-started
rs-getting-started.cpp is essentially the same script as rs-hello-realsense.cpp.  The main difference seems to be in its CMakeLists.txt build file, which is more complex than the one that rs-hello-realsense uses and includes additional instructions for finding the librealsense library.
CMakeLists.txt - rs-hello-realsense

https://github.com/IntelRealSense/librealsense/blob/master/examples/hello-realsense/CMakeLists.txt
CmakeLists.txt - rs-getting-started

https://github.com/zivsha/librealsense/blob/getting_started_example/examples/getting-started/CMakeLists.txt#L20-L31
Intel also provide an introductory level CMake example project for Linux that demonstrates simple linking to the librealsense library.
https://github.com/IntelRealSense/librealsense/tree/master/examples/cmake
The concept explained in that project of using the target_link_libraries instruction to create linkages to librealsense is also discussed at #4277 (comment)
          
Thanks for your help, after doing the getting started procedure, it works.
I have one more question, after cloning the getting-started-examples branch I look for the /examples/getting-started folder and I can't find it. Is it normal ? I must copy every file by hand to make it work.
Thanks again for your help.
          
I suspect that the default 'git clone' command is cloning the master branch that does not have the getting-started-examples folder, and you need to configure the git clone command to clone a specific branch - getting-started-example - instead.
https://devconnected.com/how-to-clone-a-git-repository/#Git_clone_a_specific_branch
          
I got an other similar issue, after that I try to compile the capture exemple with the same method from the getting started example, but when I execute the make -j4 command nothing append and the executable file is not genrated.
This is what I did. I know that I also run the example with the rs-capture command in my terminal, but I want to be able to add some modification to it.
remi@remi-desktop:~/Desktop/Realsense/librealsense/examples/capture$ ls
build  CMakeLists.txt  readme.md  rs-capture.cpp
remi@remi-desktop:~/Desktop/Realsense/librealsense/examples/capture$ cd build/
remi@remi-desktop:~/Desktop/Realsense/librealsense/examples/capture/build$ ls
remi@remi-desktop:~/Desktop/Realsense/librealsense/examples/capture/build$ cmake ../
-- The C compiler identification is GNU 7.5.0
-- The CXX compiler identification is GNU 7.5.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Performing Test COMPILER_SUPPORTS_CXX11
-- Performing Test COMPILER_SUPPORTS_CXX11 - Success
-- Performing Test COMPILER_SUPPORTS_CXX0X
-- Performing Test COMPILER_SUPPORTS_CXX0X - Success
-- Configuring done
-- Generating done
-- Build files have been written to: /home/remi/Desktop/Realsense/librealsense/examples/capture/build
remi@remi-desktop:~/Desktop/Realsense/librealsense/examples/capture/build$ make -j4
remi@remi-desktop:~/Desktop/Realsense/librealsense/examples/capture/build$ ls
CMakeCache.txt  CMakeFiles  cmake_install.cmake  Makefile
remi@remi-desktop:~/Desktop/Realsense/librealsense/examples/capture/build$
          
rs-hello-realsense and the getting-started example that uses the same code are text-only programs.  rs-capture is a graphical program that requires OpenGL graphics support (GLFW3) to have been enabled when building the librealsense SDK.  When building the SDK from source code, support for graphics in examples and tools is included in the SDK build if the flag -DBUILD_GRAPHICAL_EXAMPLES=true is included in the CMake build instruction.  For example:
cmake ../ -DCMAKE_BUILD_TYPE=release -DBUILD_EXAMPLES=true -DBUILD_GRAPHICAL_EXAMPLES=true
The need for this graphics support is referenced in the CMakeLists.txt file for the rs-capture program.
https://github.com/IntelRealSense/librealsense/blob/master/examples/capture/CMakeLists.txt#L8
          
Oh ok I understand, but does the Debian package method already did that for me ? or I should rebuild from source with the needed flag ?
Edit: I try the rs-capture command on my terminal and it work, does this mean that the OpenGL is install and should work when I build the the rs-capture.cpp example ?