Comment 15 for bug 730159

Well, the warning is printed whenever you use a copy of the 'ffmpeg' binary with a copy of libavcodec (or any other library provided by the ffmpeg source package) that has been built with a different configuration. Which is the whole point of the 'libavcodec-extra*' packages: Enable additional functionality.

To avoid the warning, the following patch should do it:

diff --git a/cmdutils.c b/cmdutils.c
index 469c2d5..6fde13b 100644
--- a/cmdutils.c
+++ b/cmdutils.c
@@ -1053,8 +1053,6 @@ void print_error(const char *filename, int err)
     av_log(NULL, AV_LOG_ERROR, "%s: %s\n", filename, errbuf_ptr);
 }

-static int warned_cfg = 0;
-
 #define INDENT 1
 #define SHOW_VERSION 2
 #define SHOW_CONFIG 4
@@ -1074,19 +1072,6 @@ static int warned_cfg = 0;
                    AV_VERSION_MAJOR(version), AV_VERSION_MINOR(version),\
                    AV_VERSION_MICRO(version)); \
         } \
- if (flags & SHOW_CONFIG) { \
- const char *cfg = libname##_configuration(); \
- if (strcmp(FFMPEG_CONFIGURATION, cfg)) { \
- if (!warned_cfg) { \
- av_log(NULL, level, \
- "%sWARNING: library configuration mismatch\n", \
- indent); \
- warned_cfg = 1; \
- } \
- av_log(NULL, level, "%s%-11s configuration: %s\n", \
- indent, #libname, cfg); \
- } \
- } \
     } \

 static void print_all_libs_info(int flags, int level)

I'm not really comfortable with uploading this patch to ubuntu, because the check was put in for preventing surprises and assisting with bug triage.

> As if the average user understands such advice, much less ever visits launchpad.

I do not think that the 'ffmpeg' command-line tool is useful to the "average [ubuntu] user". Frontend applications are going to ignore it anyways. So with this in mind, I'm inclined to mark this bug as "wontfix".