diff --git a/libavformat/rmdec.c b/libavformat/rmdec.c
index a19786b..66915cf 100644
--- a/libavformat/rmdec.c
+++ b/libavformat/rmdec.c
@@ -223,6 +223,14 @@ static int rm_read_audio_stream_info(AVFormatContext *s, AVIOContext *pb,
                     return -1;
                 }
                 st->codec->block_align = ast->sub_packet_size;
+                if (version == 4) {
+                    switch (st->codec->block_align) {
+                    case 20: st->codec->bit_rate = 16000; break;
+                    case 19: st->codec->bit_rate =  8500; break;
+                    case 29: st->codec->bit_rate =  6500; break;
+                    case 37: st->codec->bit_rate =  5000; break;
+                    }
+                }
             }
             if ((ret = rm_read_extradata(pb, st->codec, codecdata_length)) < 0)
                 return ret;