diff --git a/doc/Section_start.txt b/doc/Section_start.txt
index f905bd2e2a..6dc10cf0d2 100644
--- a/doc/Section_start.txt
+++ b/doc/Section_start.txt
@@ -183,6 +183,7 @@ within the LAMMPS code.  The options that are currently recogized are:
 -DLAMMPS_GZIP
 -DLAMMPS_JPEG
 -DLAMMPS_PNG
+-DLAMMPS_FFMPEG
 -DLAMMPS_MEMALIGN
 -DLAMMPS_XDR
 -DLAMMPS_SMALLBIG
@@ -194,8 +195,9 @@ within the LAMMPS code.  The options that are currently recogized are:
 -DPACK_MEMCPY :ul
 
 The read_data and dump commands will read/write gzipped files if you
-compile with -DLAMMPS_GZIP.  It requires that your Unix support the
-"popen" command.
+compile with -DLAMMPS_GZIP.  It requires that your machine supports the
+"popen" function in the standard runtime library and that a gzip executable
+can be found by LAMMPS during a run.
 
 If you use -DLAMMPS_JPEG, the "dump image"_dump.html command will be
 able to write out JPEG image files. For JPEG files, you must also link
@@ -203,9 +205,15 @@ LAMMPS with a JPEG library, as described below. If you use
 -DLAMMPS_PNG, the "dump image"_dump.html command will be able to write
 out PNG image files.  For PNG files, you must also link LAMMPS with a
 PNG library, as described below.  If neither of those two defines are
-used, LAMMPS will only be able to write out text-based PPM image
+used, LAMMPS will only be able to write out uncompressed PPM image
 files.
 
+If you use -DLAMMPS_FFMPEG, the "dump movie"_dump.html command will
+be available to support on-the-fly generation of rendered movies
+the need to store intermediate image files. It requires that your 
+machines supports the "popen" function in the standard runtime library
+and that an FFmpeg executable can be found by LAMMPS during the run.
+
 Using -DLAMMPS_MEMALIGN=<bytes> enables the use of the
 posix_memalign() call instead of malloc() when large chunks or memory
 are allocated by LAMMPS.  This can help to make more efficient use of
diff --git a/doc/dump_image.txt b/doc/dump_image.txt
index 6e422427eb..6affa46f26 100644
--- a/doc/dump_image.txt
+++ b/doc/dump_image.txt
@@ -373,9 +373,10 @@ shading is performed.
 
 :line
 
-A series of JPG or PPM images can be converted into a movie file and
-then played as a movie using commonly available tools. Using the 
-movie dump style skips this intermediate step
+A series of JPG, PNG, or PPM images can be converted into a movie file
+and then played as a movie using commonly available tools. Using the 
+movie dump style skips this intermediate step, but requires LAMMPS to
+be compiled with -DLAMMPS_FFMPEG and an FFmpeg executable installed.
 
 Convert JPG or PPM files into an animated GIF or MPEG or other movie
 file:
@@ -427,10 +428,14 @@ per-atom quantities which could then be output into dump files.
 
 [Restrictions:]
 
-To write JPG images, you must use a -DLAMMPS_JPEG switch when building
-LAMMPS and link with a JPEG library.  See the "Making
-LAMMPS"_Section_start.html#start_2_4 section of the documentation for
-details.
+To write JPG images, you must use the -DLAMMPS_JPEG switch when building
+LAMMPS and link with a JPEG library. To write PNG images, you must 
+use the -DLAMMPS_PNG switch when building LAMMPS and link with a PNG library.
+To write {movie} dumps, you must use the -DLAMMPS_FFMPEG switch when
+building LAMMPS and have the FFmpeg executable available on the machine
+where LAMMPS is being run. See the 
+"Making LAMMPS"_Section_start.html#start_2_4 section of the documentation
+for details.
 
 [Related commands:]