diff --git a/ffmpeg.c b/ffmpeg.c
index 4277baff75..629d202257 100644
--- a/ffmpeg.c
+++ b/ffmpeg.c
@@ -2603,11 +2603,33 @@ static int transcode(AVFormatContext **output_files,
                     do_pkt_dump = 1;
                 av_log_set_level(AV_LOG_DEBUG);
             }
+            if (key == 'd' || key == 'D'){
+                int debug=0;
+                if(key == 'D') {
+                    ist = ist_table[0];
+                    debug = ist->st->codec->debug<<1;
+                    if(!debug) debug = 1;
+                    while(debug & (FF_DEBUG_DCT_COEFF|FF_DEBUG_VIS_QP|FF_DEBUG_VIS_MB_TYPE)) //unsupported, would just crash
+                        debug += debug;
+                }else
+                    scanf("%d", &debug);
+                for(i=0;i<nb_istreams;i++) {
+                    ist = ist_table[i];
+                    ist->st->codec->debug = debug;
+                }
+                for(i=0;i<nb_ostreams;i++) {
+                    ost = ost_table[i];
+                    ost->st->codec->debug = debug;
+                }
+                if(debug) av_log_set_level(AV_LOG_DEBUG);
+                fprintf(stderr,"debug=%d\n", debug);
+            }
             if (key == '?'){
                 fprintf(stderr, "key    function\n"
                                 "?      show this help\n"
                                 "+      increase verbosity\n"
                                 "-      decrease verbosity\n"
+                                "D      cycle through available debug modes\n"
                                 "h      dump packets/hex press to cycle through the 3 states\n"
                                 "q      quit\n"
                                 "s      Show QP histogram\n"