libavfilter: example audio filtering program

Based on a patch by Andrew Kelley <superjoe30@gmail.com>
Signed-off-by: Diego Biurrun <diego@biurrun.de>

.gitignore

@@ -33,6 +33,7 @@
 /doc/avoptions_format.texi
 /doc/doxy/html/
 /doc/examples/avcodec
+/doc/examples/filter_audio
 /doc/examples/metadata
 /doc/examples/output
 /doc/examples/transcode_aac

configure

@@ -1098,6 +1098,7 @@ COMPONENT_LIST="
 
 EXAMPLE_LIST="
     avcodec_example
+    filter_audio_example
     metadata_example
     output_example
     transcode_aac_example
@@ -2030,6 +2031,7 @@ scale_filter_deps="swscale"
 
 # examples
 avcodec_example_deps="avcodec avutil"
+filter_audio_example_deps="avfilter avutil"
 metadata_example_deps="avformat avutil"
 output_example_deps="avcodec avformat avutil swscale"
 transcode_aac_example_deps="avcodec avformat avresample"

doc/Makefile

@@ -16,10 +16,11 @@ DOCS-$(CONFIG_TEXI2HTML)                        += $(HTMLPAGES)
 DOCS = $(DOCS-yes)
 
 DOC_EXAMPLES-$(CONFIG_AVCODEC_EXAMPLE)          += avcodec
+DOC_EXAMPLES-$(CONFIG_FILTER_AUDIO_EXAMPLE)     += filter_audio
 DOC_EXAMPLES-$(CONFIG_METADATA_EXAMPLE)         += metadata
 DOC_EXAMPLES-$(CONFIG_OUTPUT_EXAMPLE)           += output
 DOC_EXAMPLES-$(CONFIG_TRANSCODE_AAC_EXAMPLE)    += transcode_aac
-ALL_DOC_EXAMPLES = avcodec metadata output transcode_aac
+ALL_DOC_EXAMPLES = avcodec filter_audio metadata output transcode_aac
 
 DOC_EXAMPLES     := $(DOC_EXAMPLES-yes:%=doc/examples/%$(EXESUF))
 ALL_DOC_EXAMPLES := $(ALL_DOC_EXAMPLES:%=doc/examples/%$(EXESUF))