diff --git a/webif/html/browse/audio/audio.jim b/webif/html/browse/audio/audio.jim
index 8ff01dc..f38a322 100755
--- a/webif/html/browse/audio/audio.jim
+++ b/webif/html/browse/audio/audio.jim
@@ -10,12 +10,24 @@ jscss audio.js
 header
 
 set s [settings]
-set type [$s audiomp3descr [$s audiomp3]]
+set slow [$s audiomp3]
+set type [$s audiomp3descr $slow]
 
 set rfile [cgi_get file]
 set ts [ts fetch $rfile]
 set dir [file dirname $rfile]
-set len [$ts duration 1]
+# guess output size based on video file size
+set asize [$ts size]
+# using slight overestimates of typical audio:video size ratio
+if {[$ts get mpeglevel] eq 4} {
+   	if {$slow} { # aac-> mp3
+   		set asize [expr $asize*0.12]
+    } else { # aac-> loas
+        set asize [expr $asize*0.09]
+    }
+} else { # mp2 -> mp[23] (similar)
+    set asize [expr $asize*0.07]
+}
 
 puts "
 
@@ -30,6 +42,7 @@ puts "
 <span class=hidden id=params
     dir=\"[cgi_quote_url $dir]\"
     rfile=\"[cgi_quote_url $rfile]\"
+    asize=\"[cgi_quote_url $asize]\"
 ></span>
 
 <div id=audiodiv style=\"padding: 1em\">