diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
index 5a19a09d9a63ccfcb4967c0eba85d1e47203b531..10f3012cdcb05ea2d57d8c4123fc6ec322083e45 100644
--- a/fftools/ffmpeg.c
+++ b/fftools/ffmpeg.c
@@ -1236,8 +1236,12 @@ static void do_video_out(OutputFile *of,
         in_picture->quality = enc->global_quality;
         in_picture->pict_type = 0;
 
+        if (ost->forced_kf_ref_pts == AV_NOPTS_VALUE &&
+            in_picture->pts != AV_NOPTS_VALUE)
+            ost->forced_kf_ref_pts = in_picture->pts;
+
         pts_time = in_picture->pts != AV_NOPTS_VALUE ?
-            in_picture->pts * av_q2d(enc->time_base) : NAN;
+            (in_picture->pts - ost->forced_kf_ref_pts) * av_q2d(enc->time_base) : NAN;
         if (ost->forced_kf_index < ost->forced_kf_count &&
             in_picture->pts >= ost->forced_kf_pts[ost->forced_kf_index]) {
             ost->forced_kf_index++;
diff --git a/fftools/ffmpeg.h b/fftools/ffmpeg.h
index d44b7a5c72a52e843fb84131c35d773b6d639b97..eb1eaf63633bcf284055bb647322d068d0a9e19b 100644
--- a/fftools/ffmpeg.h
+++ b/fftools/ffmpeg.h
@@ -484,6 +484,7 @@ typedef struct OutputStream {
     AVRational frame_aspect_ratio;
 
     /* forced key frames */
+    int64_t forced_kf_ref_pts;
     int64_t *forced_kf_pts;
     int forced_kf_count;
     int forced_kf_index;
diff --git a/fftools/ffmpeg_opt.c b/fftools/ffmpeg_opt.c
index 8ae68aec0e01947b2301b10df6572248ea819617..36bce4465ac2b7da293a2e51dadf7354203847fa 100644
--- a/fftools/ffmpeg_opt.c
+++ b/fftools/ffmpeg_opt.c
@@ -1324,6 +1324,7 @@ static OutputStream *new_output_stream(OptionsContext *o, AVFormatContext *oc, e
     ost->file_index = nb_output_files - 1;
     ost->index      = idx;
     ost->st         = st;
+    ost->forced_kf_ref_pts = AV_NOPTS_VALUE;
     st->codecpar->codec_type = type;
 
     ret = choose_encoder(o, oc, ost);