diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
index 4ce31d8440..6cd92a71c1 100644
--- a/fftools/ffmpeg.c
+++ b/fftools/ffmpeg.c
@@ -3628,85 +3628,6 @@ static void reset_eagain(void)
         output_streams[i]->unavailable = 0;
 }
 
-// set duration to max(tmp, duration) in a proper time base and return duration's time_base
-static AVRational duration_max(int64_t tmp, int64_t *duration, AVRational tmp_time_base,
-                               AVRational time_base)
-{
-    int ret;
-
-    if (!*duration) {
-        *duration = tmp;
-        return tmp_time_base;
-    }
-
-    ret = av_compare_ts(*duration, time_base, tmp, tmp_time_base);
-    if (ret < 0) {
-        *duration = tmp;
-        return tmp_time_base;
-    }
-
-    return time_base;
-}
-
-static int seek_to_start(InputFile *ifile, AVFormatContext *is)
-{
-    InputStream *ist;
-    AVCodecContext *avctx;
-    int i, ret, has_audio = 0;
-    int64_t duration = 0;
-
-    ret = avformat_seek_file(is, -1, INT64_MIN, is->start_time, is->start_time, 0);
-    if (ret < 0)
-        return ret;
-
-    for (i = 0; i < ifile->nb_streams; i++) {
-        ist   = input_streams[ifile->ist_index + i];
-        avctx = ist->dec_ctx;
-
-        /* duration is the length of the last frame in a stream
-         * when audio stream is present we don't care about
-         * last video frame length because it's not defined exactly */
-        if (avctx->codec_type == AVMEDIA_TYPE_AUDIO && ist->nb_samples)
-            has_audio = 1;
-    }
-
-    for (i = 0; i < ifile->nb_streams; i++) {
-        ist   = input_streams[ifile->ist_index + i];
-        avctx = ist->dec_ctx;
-
-        if (has_audio) {
-            if (avctx->codec_type == AVMEDIA_TYPE_AUDIO && ist->nb_samples) {
-                AVRational sample_rate = {1, avctx->sample_rate};
-
-                duration = av_rescale_q(ist->nb_samples, sample_rate, ist->st->time_base);
-            } else {
-                continue;
-            }
-        } else {
-            if (ist->framerate.num) {
-                duration = av_rescale_q(1, av_inv_q(ist->framerate), ist->st->time_base);
-            } else if (ist->st->avg_frame_rate.num) {
-                duration = av_rescale_q(1, av_inv_q(ist->st->avg_frame_rate), ist->st->time_base);
-            } else {
-                duration = 1;
-            }
-        }
-        if (!ifile->duration)
-            ifile->time_base = ist->st->time_base;
-        /* the total duration of the stream, max_pts - min_pts is
-         * the duration of the stream without the last frame */
-        if (ist->max_pts > ist->min_pts && ist->max_pts - (uint64_t)ist->min_pts < INT64_MAX - duration)
-            duration += ist->max_pts - ist->min_pts;
-        ifile->time_base = duration_max(duration, &ifile->duration, ist->st->time_base,
-                                        ifile->time_base);
-    }
-
-    if (ifile->loop > 0)
-        ifile->loop--;
-
-    return ret;
-}
-
 /*
  * Return
  * - 0 -- one packet was read and processed
diff --git a/fftools/ffmpeg.h b/fftools/ffmpeg.h
index f983d077d9..2a9c34eb93 100644
--- a/fftools/ffmpeg.h
+++ b/fftools/ffmpeg.h
@@ -715,5 +715,6 @@ int init_input_threads(void);
 int init_input_thread(int i);
 void free_input_threads(void);
 void free_input_thread(int i);
+int seek_to_start(InputFile *ifile, AVFormatContext *is);
 
 #endif /* FFTOOLS_FFMPEG_H */
diff --git a/fftools/ffmpeg_demux.c b/fftools/ffmpeg_demux.c
index 182364dae5..bfdb209f00 100644
--- a/fftools/ffmpeg_demux.c
+++ b/fftools/ffmpeg_demux.c
@@ -42,6 +42,85 @@ static void report_new_stream(InputFile *file, const AVPacket *pkt)
     file->nb_streams_warn = pkt->stream_index + 1;
 }
 
+// set duration to max(tmp, duration) in a proper time base and return duration's time_base
+static AVRational duration_max(int64_t tmp, int64_t *duration, AVRational tmp_time_base,
+                               AVRational time_base)
+{
+    int ret;
+
+    if (!*duration) {
+        *duration = tmp;
+        return tmp_time_base;
+    }
+
+    ret = av_compare_ts(*duration, time_base, tmp, tmp_time_base);
+    if (ret < 0) {
+        *duration = tmp;
+        return tmp_time_base;
+    }
+
+    return time_base;
+}
+
+int seek_to_start(InputFile *ifile, AVFormatContext *is)
+{
+    InputStream *ist;
+    AVCodecContext *avctx;
+    int i, ret, has_audio = 0;
+    int64_t duration = 0;
+
+    ret = avformat_seek_file(is, -1, INT64_MIN, is->start_time, is->start_time, 0);
+    if (ret < 0)
+        return ret;
+
+    for (i = 0; i < ifile->nb_streams; i++) {
+        ist   = input_streams[ifile->ist_index + i];
+        avctx = ist->dec_ctx;
+
+        /* duration is the length of the last frame in a stream
+         * when audio stream is present we don't care about
+         * last video frame length because it's not defined exactly */
+        if (avctx->codec_type == AVMEDIA_TYPE_AUDIO && ist->nb_samples)
+            has_audio = 1;
+    }
+
+    for (i = 0; i < ifile->nb_streams; i++) {
+        ist   = input_streams[ifile->ist_index + i];
+        avctx = ist->dec_ctx;
+
+        if (has_audio) {
+            if (avctx->codec_type == AVMEDIA_TYPE_AUDIO && ist->nb_samples) {
+                AVRational sample_rate = {1, avctx->sample_rate};
+
+                duration = av_rescale_q(ist->nb_samples, sample_rate, ist->st->time_base);
+            } else {
+                continue;
+            }
+        } else {
+            if (ist->framerate.num) {
+                duration = av_rescale_q(1, av_inv_q(ist->framerate), ist->st->time_base);
+            } else if (ist->st->avg_frame_rate.num) {
+                duration = av_rescale_q(1, av_inv_q(ist->st->avg_frame_rate), ist->st->time_base);
+            } else {
+                duration = 1;
+            }
+        }
+        if (!ifile->duration)
+            ifile->time_base = ist->st->time_base;
+        /* the total duration of the stream, max_pts - min_pts is
+         * the duration of the stream without the last frame */
+        if (ist->max_pts > ist->min_pts && ist->max_pts - (uint64_t)ist->min_pts < INT64_MAX - duration)
+            duration += ist->max_pts - ist->min_pts;
+        ifile->time_base = duration_max(duration, &ifile->duration, ist->st->time_base,
+                                        ifile->time_base);
+    }
+
+    if (ifile->loop > 0)
+        ifile->loop--;
+
+    return ret;
+}
+
 static void *input_thread(void *arg)
 {
     InputFile *f = arg;