lavfi: add an audio buffer source.

doc/filters.texi

@@ -151,6 +151,33 @@ anullsrc=48000:4
 anullsrc=48000:mono
 @end example
 
+@section abuffer
+Buffer audio frames, and make them available to the filter chain.
+
+This source is not intended to be part of user-supplied graph descriptions but
+for insertion by calling programs through the interface defined in
+@file{libavfilter/buffersrc.h}.
+
+It accepts the following named parameters:
+@table @option
+
+@item time_base
+Timebase which will be used for timestamps of submitted frames. It must be
+either a floating-point number or in @var{numerator}/@var{denominator} form.
+
+@item sample_rate
+Audio sample rate.
+
+@item sample_fmt
+Name of the sample format, as returned by @code{av_get_sample_fmt_name()}.
+
+@item channel_layout
+Channel layout of the audio data, in the form that can be accepted by
+@code{av_get_channel_layout()}.
+@end table
+
+All the parameters need to be explicitly defined.
+
 @c man end AUDIO SOURCES
 
 @chapter Audio Sinks

libavfilter/allfilters.c

@@ -95,6 +95,10 @@ void avfilter_register_all(void)
         extern AVFilter avfilter_vsrc_buffer;
         avfilter_register(&avfilter_vsrc_buffer);
     }
+    {
+        extern AVFilter avfilter_asrc_abuffer;
+        avfilter_register(&avfilter_asrc_abuffer);
+    }
     {
         extern AVFilter avfilter_vsink_buffer;
         avfilter_register(&avfilter_vsink_buffer);