diff --git a/libavformat/rmdec.c b/libavformat/rmdec.c
index a19786b..b9eb55b 100644
--- a/libavformat/rmdec.c
+++ b/libavformat/rmdec.c
@@ -217,6 +217,14 @@ static int rm_read_audio_stream_info(AVFormatContext *s, AVIOContext *pb,
                     return -1;
                 }
                 st->codec->block_align = ff_sipr_subpk_size[flavor];
+                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;
+                    }
+                }
             } else {
                 if(sub_packet_size <= 0){
                     av_log(s, AV_LOG_ERROR, "sub_packet_size is invalid\n");