the output buffer size may be less than FF_MIN_BUFFER_SIZE.
Patch by John Fletcher john.surname AT rd . bbc . co . uk.
Originally committed as revision 18449 to svn://svn.ffmpeg.org/ffmpeg/trunk
* stored in output buffer \p buf.
*
* @note The output buffer should be at least \c FF_MIN_BUFFER_SIZE bytes large.
+ * However, for PCM audio the user will know how much space is needed
+ * because it depends on the value passed in \p buf_size as described
+ * below. In that case a lower value can be used.
*
* @param avctx the codec context
* @param[out] buf the output buffer