diff --git a/doc/src/Developer_comm_ops.rst b/doc/src/Developer_comm_ops.rst index f8444d2993..116b4d6ad8 100644 --- a/doc/src/Developer_comm_ops.rst +++ b/doc/src/Developer_comm_ops.rst @@ -77,7 +77,7 @@ buffer, and they will be communicated together to minimize communication overhead. The communication buffers are defined vectors containing ``double`` values. To correctly store integers that may be 64-bit (bigint, tagint, imageint) in the buffer, you need to use the -`ubuf union `_ construct. +:ref:`ubuf union ` construct. The *Fix*, *Compute*, and *Dump* classes can also invoke the same kind of forward and reverse communication operations using the same *Comm* diff --git a/doc/src/Developer_utils.rst b/doc/src/Developer_utils.rst index 53ec0ad343..625ce15202 100644 --- a/doc/src/Developer_utils.rst +++ b/doc/src/Developer_utils.rst @@ -643,6 +643,8 @@ Tohoku University (under MIT license) --------------------------- +.. _communication_buffer_coding_with_ubuf: + Communication buffer coding with *ubuf* --------------------------------------- diff --git a/doc/src/Howto_wsl.rst b/doc/src/Howto_wsl.rst index df5644451f..fbb75d9cfd 100644 --- a/doc/src/Howto_wsl.rst +++ b/doc/src/Howto_wsl.rst @@ -11,12 +11,14 @@ LAMMPS in workshop settings, we had to redirect Windows users to Linux Virtual Machines such as VirtualBox or Unix-like compilation with Cygwin. -With the latest updates in Windows 10 (Version 2004, Build 19041 or higher), -Microsoft has added a new way to work on Linux-based code. The Windows -Subsystem for Linux (WSL). With WSL Version 2, you now get a Linux Virtual -Machine that transparently integrates into Windows. All you need is to ensure -you have the latest Windows updates installed and enable this new feature. -Linux VMs are then easily installed using the Microsoft Store. +With the latest updates in Windows 10 (Version 2004, Build 19041 or +higher), Microsoft has added a new way to work on Linux-based code. The +`Windows Subsystem for Linux (WSL) +`_. With WSL Version 2, +you now get a Linux Virtual Machine that transparently integrates into +Windows. All you need is to ensure you have the latest Windows updates +installed and enable this new feature. Linux VMs are then easily +installed using the Microsoft Store. In this tutorial, I'll show you how to set up and compile LAMMPS for both serial and MPI usage in WSL2. diff --git a/doc/src/Packages_details.rst b/doc/src/Packages_details.rst index 74b4eacf8f..c9f19f4988 100644 --- a/doc/src/Packages_details.rst +++ b/doc/src/Packages_details.rst @@ -228,8 +228,9 @@ conversion of atomic information to continuum fields. **Install:** -This package has :ref:`specific installation instructions ` on the :doc:`Build extras ` page. -The ATC package requires that also the `MANYBODY `_ package is installed. +This package has :ref:`specific installation instructions ` on the +:doc:`Build extras ` page. The ATC package requires that +also the :ref:`MANYBODY ` package is installed. **Supporting info:** @@ -391,8 +392,8 @@ rigid-body integrators with improved stability. **Install:** -The CG-DNA package requires that also the `MOLECULE `_ and -`ASPHERE `_ packages are installed. +The CG-DNA package requires that also the :ref:`MOLECULE ` +and :ref:`ASPHERE ` packages are installed. **Supporting info:** @@ -1114,15 +1115,15 @@ INTEL package **Contents:** -Dozens of pair, fix, bond, angle, dihedral, improper, and kspace -styles which are optimized for Intel CPUs and KNLs (Knights Landing). -All of them have an "intel" in their style name. The -:doc:`INTEL package ` page gives details of what hardware and -compilers are required on your system, and how to build and use this -package. Its styles can be invoked at run time via the "-sf intel" or -"-suffix intel" :doc:`command-line switches `. Also see -the :ref:`KOKKOS `, :ref:`OPT `, and :ref:`OPENMP ` packages, -which have styles optimized for CPUs and KNLs. +Dozens of pair, fix, bond, angle, dihedral, improper, and kspace styles +which are optimized for Intel CPUs and KNLs (Knights Landing). All of +them have an "intel" in their style name. The :doc:`INTEL package +` page gives details of what hardware and compilers are +required on your system, and how to build and use this package. Its +styles can be invoked at run time via the "-sf intel" or "-suffix intel" +:doc:`command-line switches `. Also see the :ref:`KOKKOS +`, :ref:`OPT `, and :ref:`OPENMP ` +packages, which have styles optimized for CPUs and KNLs. You need to have an Intel compiler, version 14 or higher to take full advantage of this package. While compilation with GNU compilers is @@ -1249,12 +1250,13 @@ Dozens of atom, pair, bond, angle, dihedral, improper, fix, compute styles adapted to compile using the Kokkos library which can convert them to OpenMP or CUDA code so that they run efficiently on multicore CPUs, KNLs, or GPUs. All the styles have a "kk" as a suffix in their -style name. The :doc:`KOKKOS package ` page gives -details of what hardware and software is required on your system, and -how to build and use this package. Its styles can be invoked at run -time via the "-sf kk" or "-suffix kk" :doc:`command-line switches `. Also see the :ref:`GPU `, :ref:`OPT `, -:ref:`INTEL `, and :ref:`OPENMP ` packages, which -have styles optimized for CPUs, KNLs, and GPUs. +style name. The :doc:`KOKKOS package ` page gives details +of what hardware and software is required on your system, and how to +build and use this package. Its styles can be invoked at run time via +the "-sf kk" or "-suffix kk" :doc:`command-line switches `. +Also see the :ref:`GPU `, :ref:`OPT `, :ref:`INTEL +`, and :ref:`OPENMP ` packages, which have styles +optimized for CPUs, KNLs, and GPUs. You must have a C++14 compatible compiler to use this package. KOKKOS makes extensive use of advanced C++ features, which can @@ -2328,7 +2330,7 @@ and third order tensor from finite differences. **Install:** -The PHONON package requires that also the `KSPACE `_ +The PHONON package requires that also the :ref:`KSPACE ` package is installed. @@ -2929,11 +2931,9 @@ VORONOI package **Contents:** A compute command which calculates the Voronoi tesselation of a -collection of atoms by wrapping the `Voro++ library `_. This -can be used to calculate the local volume or each atoms or its near -neighbors. - -.. _voro-home: https://math.lbl.gov/voro++ +collection of atoms by wrapping the `Voro++ library +`_. This can be used to calculate the +local volume or each atoms or its near neighbors. To use this package you must have the Voro++ library available on your system. diff --git a/doc/src/compute_smd_contact_radius.rst b/doc/src/compute_smd_contact_radius.rst index 25f346625c..4911ac4e27 100644 --- a/doc/src/compute_smd_contact_radius.rst +++ b/doc/src/compute_smd_contact_radius.rst @@ -29,7 +29,7 @@ contact radius is used only to prevent particles belonging to different physical bodies from penetrating each other. It is used by the contact pair styles, e.g., smd/hertz and smd/tri_surface. -See `this PDF guide `_ to using Smooth +See `this PDF guide `_ to using Smooth Mach Dynamics in LAMMPS. The value of the contact radius will be 0.0 for particles not in the diff --git a/doc/src/compute_smd_damage.rst b/doc/src/compute_smd_damage.rst index 10070eaf0e..fe5d94fa83 100644 --- a/doc/src/compute_smd_damage.rst +++ b/doc/src/compute_smd_damage.rst @@ -26,7 +26,7 @@ Description Define a computation that calculates the damage status of SPH particles according to the damage model which is defined via the SMD SPH pair styles, e.g., the maximum plastic strain failure criterion. -See `this PDF guide `_ to use Smooth Mach Dynamics in LAMMPS. +See `this PDF guide `_ to use Smooth Mach Dynamics in LAMMPS. **Output Info:** diff --git a/doc/src/compute_smd_hourglass_error.rst b/doc/src/compute_smd_hourglass_error.rst index aee87592aa..7e0aadd6d2 100644 --- a/doc/src/compute_smd_hourglass_error.rst +++ b/doc/src/compute_smd_hourglass_error.rst @@ -34,7 +34,7 @@ configuration. This compute is only really useful for debugging the hourglass control mechanism which is part of the Total-Lagrangian SPH pair style. -See `this PDF guide `_ to use Smooth +See `this PDF guide `_ to use Smooth Mach Dynamics in LAMMPS. **Output Info:** diff --git a/doc/src/compute_smd_internal_energy.rst b/doc/src/compute_smd_internal_energy.rst index 535384e38b..36bd816e8f 100644 --- a/doc/src/compute_smd_internal_energy.rst +++ b/doc/src/compute_smd_internal_energy.rst @@ -26,7 +26,7 @@ Description Define a computation which outputs the per-particle enthalpy, i.e., the sum of potential energy and heat. -See `this PDF guide `_ to use Smooth +See `this PDF guide `_ to use Smooth Mach Dynamics in LAMMPS. Output Info diff --git a/doc/src/compute_smd_plastic_strain.rst b/doc/src/compute_smd_plastic_strain.rst index 17614df548..00c6cb9a4a 100644 --- a/doc/src/compute_smd_plastic_strain.rst +++ b/doc/src/compute_smd_plastic_strain.rst @@ -27,7 +27,7 @@ Define a computation that outputs the equivalent plastic strain per particle. This command is only meaningful if a material model with plasticity is defined. -See `this PDF guide `_ to use Smooth +See `this PDF guide `_ to use Smooth Mach Dynamics in LAMMPS. **Output Info:** diff --git a/doc/src/compute_smd_plastic_strain_rate.rst b/doc/src/compute_smd_plastic_strain_rate.rst index dc78b627ef..681573be9b 100644 --- a/doc/src/compute_smd_plastic_strain_rate.rst +++ b/doc/src/compute_smd_plastic_strain_rate.rst @@ -27,7 +27,7 @@ Define a computation that outputs the time rate of the equivalent plastic strain. This command is only meaningful if a material model with plasticity is defined. -See `this PDF guide `_ to use Smooth +See `this PDF guide `_ to use Smooth Mach Dynamics in LAMMPS. **Output Info:** diff --git a/doc/src/compute_smd_rho.rst b/doc/src/compute_smd_rho.rst index 0adbc9db34..605dd5b79c 100644 --- a/doc/src/compute_smd_rho.rst +++ b/doc/src/compute_smd_rho.rst @@ -28,7 +28,7 @@ The mass density is the mass of a particle which is constant during the course of a simulation, divided by its volume, which can change due to mechanical deformation. -See `this PDF guide `_ to use Smooth +See `this PDF guide `_ to use Smooth Mach Dynamics in LAMMPS. Output info diff --git a/doc/src/compute_smd_tlsph_defgrad.rst b/doc/src/compute_smd_tlsph_defgrad.rst index 813bd32507..399e54d055 100644 --- a/doc/src/compute_smd_tlsph_defgrad.rst +++ b/doc/src/compute_smd_tlsph_defgrad.rst @@ -27,7 +27,7 @@ Define a computation that calculates the deformation gradient. It is only meaningful for particles which interact according to the Total-Lagrangian SPH pair style. -See `this PDF guide `_ to use Smooth +See `this PDF guide `_ to use Smooth Mach Dynamics in LAMMPS. Output info diff --git a/doc/src/compute_smd_tlsph_dt.rst b/doc/src/compute_smd_tlsph_dt.rst index 44b2311898..9490f7da14 100644 --- a/doc/src/compute_smd_tlsph_dt.rst +++ b/doc/src/compute_smd_tlsph_dt.rst @@ -32,7 +32,7 @@ time step. This calculation is performed automatically in the relevant SPH pair styles and this compute only serves to make the stable time increment accessible for output purposes. -See `this PDF guide `_ to using Smooth +See `this PDF guide `_ to using Smooth Mach Dynamics in LAMMPS. Output info diff --git a/doc/src/compute_smd_tlsph_num_neighs.rst b/doc/src/compute_smd_tlsph_num_neighs.rst index bc76ec260f..ef8c19d49c 100644 --- a/doc/src/compute_smd_tlsph_num_neighs.rst +++ b/doc/src/compute_smd_tlsph_num_neighs.rst @@ -27,7 +27,7 @@ Define a computation that calculates the number of particles inside of the smoothing kernel radius for particles interacting via the Total-Lagrangian SPH pair style. -See `this PDF guide `_ to using Smooth +See `this PDF guide `_ to using Smooth Mach Dynamics in LAMMPS. Output info diff --git a/doc/src/compute_smd_tlsph_shape.rst b/doc/src/compute_smd_tlsph_shape.rst index aefedb64eb..4a5abd868b 100644 --- a/doc/src/compute_smd_tlsph_shape.rst +++ b/doc/src/compute_smd_tlsph_shape.rst @@ -28,7 +28,7 @@ associated with a particle as a rotated ellipsoid. It is only meaningful for particles which interact according to the Total-Lagrangian SPH pair style. -See `this PDF guide `_ to use Smooth +See `this PDF guide `_ to use Smooth Mach Dynamics in LAMMPS. Output info diff --git a/doc/src/compute_smd_tlsph_strain.rst b/doc/src/compute_smd_tlsph_strain.rst index 3ecb509e9f..053488886b 100644 --- a/doc/src/compute_smd_tlsph_strain.rst +++ b/doc/src/compute_smd_tlsph_strain.rst @@ -26,7 +26,7 @@ Description Define a computation that calculates the Green-Lagrange strain tensor for particles interacting via the Total-Lagrangian SPH pair style. -See `this PDF guide `_ to using Smooth +See `this PDF guide `_ to using Smooth Mach Dynamics in LAMMPS. Output info diff --git a/doc/src/compute_smd_tlsph_strain_rate.rst b/doc/src/compute_smd_tlsph_strain_rate.rst index 41251d7095..2f3d561cee 100644 --- a/doc/src/compute_smd_tlsph_strain_rate.rst +++ b/doc/src/compute_smd_tlsph_strain_rate.rst @@ -26,7 +26,7 @@ Description Define a computation that calculates the rate of the strain tensor for particles interacting via the Total-Lagrangian SPH pair style. -See `this PDF guide `_ to using Smooth +See `this PDF guide `_ to using Smooth Mach Dynamics in LAMMPS. Output info diff --git a/doc/src/compute_smd_tlsph_stress.rst b/doc/src/compute_smd_tlsph_stress.rst index 11cec3bda8..4f0473f30a 100644 --- a/doc/src/compute_smd_tlsph_stress.rst +++ b/doc/src/compute_smd_tlsph_stress.rst @@ -26,7 +26,7 @@ Description Define a computation that outputs the Cauchy stress tensor for particles interacting via the Total-Lagrangian SPH pair style. -See `this PDF guide `_ to using Smooth +See `this PDF guide `_ to using Smooth Mach Dynamics in LAMMPS. Output info diff --git a/doc/src/compute_smd_triangle_vertices.rst b/doc/src/compute_smd_triangle_vertices.rst index d1aebfb29e..309c4260e9 100644 --- a/doc/src/compute_smd_triangle_vertices.rst +++ b/doc/src/compute_smd_triangle_vertices.rst @@ -26,7 +26,7 @@ Description Define a computation that returns the coordinates of the vertices corresponding to the triangle-elements of a mesh created by the :doc:`fix smd/wall_surface `. -See `this PDF guide `_ to using Smooth +See `this PDF guide `_ to using Smooth Mach Dynamics in LAMMPS. Output info diff --git a/doc/src/compute_smd_ulsph_effm.rst b/doc/src/compute_smd_ulsph_effm.rst index 4b4959fbe1..2d2b85ca21 100644 --- a/doc/src/compute_smd_ulsph_effm.rst +++ b/doc/src/compute_smd_ulsph_effm.rst @@ -26,7 +26,7 @@ Description Define a computation that outputs the effective shear modulus for particles interacting via the updated Lagrangian SPH pair style. -See `this PDF guide `_ to using Smooth +See `this PDF guide `_ to using Smooth Mach Dynamics in LAMMPS. Output info diff --git a/doc/src/compute_smd_ulsph_num_neighs.rst b/doc/src/compute_smd_ulsph_num_neighs.rst index c446c477c0..b7592fee9f 100644 --- a/doc/src/compute_smd_ulsph_num_neighs.rst +++ b/doc/src/compute_smd_ulsph_num_neighs.rst @@ -27,7 +27,7 @@ Define a computation that returns the number of neighbor particles inside of the smoothing kernel radius for particles interacting via the updated Lagrangian SPH pair style. -See `this PDF guide `_ to using Smooth +See `this PDF guide `_ to using Smooth Mach Dynamics in LAMMPS. Output info diff --git a/doc/src/compute_smd_ulsph_strain.rst b/doc/src/compute_smd_ulsph_strain.rst index 31defe4b32..9ece72c35c 100644 --- a/doc/src/compute_smd_ulsph_strain.rst +++ b/doc/src/compute_smd_ulsph_strain.rst @@ -26,7 +26,7 @@ Description Define a computation that outputs the logarithmic strain tensor. for particles interacting via the updated Lagrangian SPH pair style. -See `this PDF guide `_ to using Smooth +See `this PDF guide `_ to using Smooth Mach Dynamics in LAMMPS. Output info diff --git a/doc/src/compute_smd_ulsph_strain_rate.rst b/doc/src/compute_smd_ulsph_strain_rate.rst index 0a2ca91081..69e1040065 100644 --- a/doc/src/compute_smd_ulsph_strain_rate.rst +++ b/doc/src/compute_smd_ulsph_strain_rate.rst @@ -27,7 +27,7 @@ Define a computation that outputs the rate of the logarithmic strain tensor for particles interacting via the updated Lagrangian SPH pair style. -See `this PDF guide `_ to using Smooth +See `this PDF guide `_ to using Smooth Mach Dynamics in LAMMPS. Output info diff --git a/doc/src/compute_smd_ulsph_stress.rst b/doc/src/compute_smd_ulsph_stress.rst index a993a08c06..55f411158c 100644 --- a/doc/src/compute_smd_ulsph_stress.rst +++ b/doc/src/compute_smd_ulsph_stress.rst @@ -25,7 +25,7 @@ Description Define a computation that outputs the Cauchy stress tensor. -See `this PDF guide `_ to using Smooth +See `this PDF guide `_ to using Smooth Mach Dynamics in LAMMPS. Output info diff --git a/doc/src/compute_smd_vol.rst b/doc/src/compute_smd_vol.rst index f09c48e0ed..d31eb53785 100644 --- a/doc/src/compute_smd_vol.rst +++ b/doc/src/compute_smd_vol.rst @@ -26,7 +26,7 @@ Description Define a computation that provides the per-particle volume and the sum of the per-particle volumes of the group for which the fix is defined. -See `this PDF guide `_ to using Smooth +See `this PDF guide `_ to using Smooth Mach Dynamics in LAMMPS. Output info diff --git a/doc/src/fix_ave_spatial.rst b/doc/src/fix_ave_spatial.rst index 96d87bd8db..14c1518fd9 100644 --- a/doc/src/fix_ave_spatial.rst +++ b/doc/src/fix_ave_spatial.rst @@ -2,7 +2,7 @@ Fix ave/spatial command ======================= .. meta:: - :http-equiv=Refresh: 5; url='https://docs.lammps.org/Commands_removed.html#fix-ave-spatial-and-fix-ave-spatial-sphere' + :http-equiv=Refresh: 5; url=Commands_removed.html#fix-ave-spatial-and-fix-ave-spatial-sphere .. deprecated:: 11Dec2015 diff --git a/doc/src/fix_ave_spatial_sphere.rst b/doc/src/fix_ave_spatial_sphere.rst index a3cacc4115..c83b7c7f27 100644 --- a/doc/src/fix_ave_spatial_sphere.rst +++ b/doc/src/fix_ave_spatial_sphere.rst @@ -2,7 +2,7 @@ Fix ave/spatial command ======================= .. meta:: - :http-equiv=Refresh: 5; url='https://docs.lammps.org/Commands_removed.html#fix-ave-spatial-and-fix-ave-spatial-sphere' + :http-equiv=Refresh: 5; url=https://docs.lammps.org/Commands_removed.html#fix-ave-spatial-and-fix-ave-spatial-sphere .. deprecated:: 11Dec2015 diff --git a/doc/src/fix_smd_adjust_dt.rst b/doc/src/fix_smd_adjust_dt.rst index 0f1be7ed24..c0487cb1f7 100644 --- a/doc/src/fix_smd_adjust_dt.rst +++ b/doc/src/fix_smd_adjust_dt.rst @@ -43,7 +43,7 @@ This fix inquires the minimum stable time increment across all particles contained in the group for which this fix is defined. An additional safety factor *s_fact* is applied to the time increment. -See `this PDF guide `_ to use Smooth Mach +See `this PDF guide `_ to use Smooth Mach Dynamics in LAMMPS. Restart, fix_modify, output, run start/stop, minimize info diff --git a/doc/src/fix_smd_integrate_tlsph.rst b/doc/src/fix_smd_integrate_tlsph.rst index c4f5e61c7e..515b30d4ff 100644 --- a/doc/src/fix_smd_integrate_tlsph.rst +++ b/doc/src/fix_smd_integrate_tlsph.rst @@ -34,7 +34,7 @@ Description The fix performs explicit time integration for particles which interact according with the Total-Lagrangian SPH pair style. -See `this PDF guide `_ to using Smooth Mach +See `this PDF guide `_ to using Smooth Mach Dynamics in LAMMPS. The *limit_velocity* keyword will control the velocity, scaling the diff --git a/doc/src/fix_smd_integrate_ulsph.rst b/doc/src/fix_smd_integrate_ulsph.rst index 8f2e0b2b88..17dfdb7b17 100644 --- a/doc/src/fix_smd_integrate_ulsph.rst +++ b/doc/src/fix_smd_integrate_ulsph.rst @@ -36,7 +36,7 @@ Description The fix performs explicit time integration for particles which interact with the updated Lagrangian SPH pair style. -See `this PDF guide `_ to using Smooth Mach +See `this PDF guide `_ to using Smooth Mach Dynamics in LAMMPS. The *adjust_radius* keyword activates dynamic adjustment of the diff --git a/doc/src/fix_smd_move_triangulated_surface.rst b/doc/src/fix_smd_move_triangulated_surface.rst index 76f7240007..2eeb5a4d56 100644 --- a/doc/src/fix_smd_move_triangulated_surface.rst +++ b/doc/src/fix_smd_move_triangulated_surface.rst @@ -60,7 +60,7 @@ particle to (omega cross Rperp) where omega is its angular velocity around the rotation axis and Rperp is a perpendicular vector from the rotation axis to the particle. -See `this PDF guide `_ to using Smooth Mach +See `this PDF guide `_ to using Smooth Mach Dynamics in LAMMPS. Restart, fix_modify, output, run start/stop, minimize info diff --git a/doc/src/fix_smd_wall_surface.rst b/doc/src/fix_smd_wall_surface.rst index 192ab7a518..203bdb0ca5 100644 --- a/doc/src/fix_smd_wall_surface.rst +++ b/doc/src/fix_smd_wall_surface.rst @@ -47,7 +47,7 @@ be run for 0 timesteps in order to properly register the new particles in the system. See the "funnel_flow" example in the MACHDYN examples directory. -See `this PDF guide `_ to use Smooth Mach +See `this PDF guide `_ to use Smooth Mach Dynamics in LAMMPS. Restart, fix_modify, output, run start/stop, minimize info diff --git a/doc/src/pair_smd_tlsph.rst b/doc/src/pair_smd_tlsph.rst index 3884b0fec3..eb6dbcf07f 100644 --- a/doc/src/pair_smd_tlsph.rst +++ b/doc/src/pair_smd_tlsph.rst @@ -48,7 +48,7 @@ and a material model to compute shear stresses (the off-diagonal components of the stress tensor). Damage and failure models can also be added. -Please see the `SMD user guide `_ for a +Please see the `SMD user guide `_ for a complete listing of the possible keywords and material models. ---------- diff --git a/doc/src/pair_smd_ulsph.rst b/doc/src/pair_smd_ulsph.rst index fd63908e3d..b6c7df0530 100644 --- a/doc/src/pair_smd_ulsph.rst +++ b/doc/src/pair_smd_ulsph.rst @@ -59,7 +59,7 @@ Note that the use of \*GRADIENT_CORRECTION can lead to severe numerical instabilities. For a general fluid simulation, \*NO_GRADIENT_CORRECTION is recommended. -Please see the `SMD user guide `_ for a +Please see the `SMD user guide `_ for a complete listing of the possible keywords and material models. ---------- diff --git a/src/library.cpp b/src/library.cpp index 1214885cd3..7fcc22ef17 100644 --- a/src/library.cpp +++ b/src/library.cpp @@ -5302,7 +5302,7 @@ int lammps_config_has_jpeg_support() { \verbatim embed:rst The LAMMPS :doc:`dump style movie ` supports generating movies from images on-the-fly via creating a pipe to the -`ffmpeg `_ program. +`ffmpeg `_ program. This function checks whether this feature was :ref:`enabled at compile time `. It does **not** check whether the ``ffmpeg`` itself is installed and usable. \endverbatim