diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
index d143244e7c..84ace5d414 100644
--- a/fftools/ffmpeg.c
+++ b/fftools/ffmpeg.c
@@ -914,85 +914,6 @@ int ifilter_parameters_from_codecpar(InputFilter *ifilter, AVCodecParameters *pa
     return 0;
 }
 
-/**
- * @param dts predicted packet dts in AV_TIME_BASE_Q
- */
-static void do_streamcopy(InputStream *ist, OutputStream *ost,
-                          const AVPacket *pkt, int64_t dts)
-{
-    OutputFile *of = output_files[ost->file_index];
-    int64_t start_time = (of->start_time == AV_NOPTS_VALUE) ? 0 : of->start_time;
-    int64_t ost_tb_start_time = av_rescale_q(start_time, AV_TIME_BASE_Q, ost->mux_timebase);
-    AVPacket *opkt = ost->pkt;
-
-    av_packet_unref(opkt);
-    // EOF: flush output bitstream filters.
-    if (!pkt) {
-        of_output_packet(of, opkt, ost, 1);
-        return;
-    }
-
-    if (!ost->streamcopy_started && !(pkt->flags & AV_PKT_FLAG_KEY) &&
-        !ost->copy_initial_nonkeyframes)
-        return;
-
-    if (!ost->streamcopy_started) {
-        if (!ost->copy_prior_start &&
-            (pkt->pts == AV_NOPTS_VALUE ?
-             dts < ost->ts_copy_start :
-             pkt->pts < av_rescale_q(ost->ts_copy_start, AV_TIME_BASE_Q, pkt->time_base)))
-            return;
-
-        if (of->start_time != AV_NOPTS_VALUE && dts < of->start_time)
-            return;
-    }
-
-    if (of->recording_time != INT64_MAX &&
-        dts >= of->recording_time + start_time) {
-        close_output_stream(ost);
-        return;
-    }
-
-    if (av_packet_ref(opkt, pkt) < 0)
-        exit_program(1);
-
-    opkt->time_base = ost->mux_timebase;
-
-    if (pkt->pts != AV_NOPTS_VALUE)
-        opkt->pts = av_rescale_q(pkt->pts, pkt->time_base, opkt->time_base) - ost_tb_start_time;
-
-    if (pkt->dts == AV_NOPTS_VALUE) {
-        opkt->dts = av_rescale_q(dts, AV_TIME_BASE_Q, opkt->time_base);
-    } else if (ost->st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) {
-        int duration = av_get_audio_frame_duration2(ist->par, pkt->size);
-        if(!duration)
-            duration = ist->par->frame_size;
-        opkt->dts = av_rescale_delta(pkt->time_base, pkt->dts,
-                                    (AVRational){1, ist->par->sample_rate}, duration,
-                                    &ist->filter_in_rescale_delta_last, opkt->time_base);
-        /* dts will be set immediately afterwards to what pts is now */
-        opkt->pts = opkt->dts - ost_tb_start_time;
-    } else
-        opkt->dts = av_rescale_q(pkt->dts, pkt->time_base, opkt->time_base);
-    opkt->dts -= ost_tb_start_time;
-
-    opkt->duration = av_rescale_q(pkt->duration, pkt->time_base, opkt->time_base);
-
-    {
-        int ret = trigger_fix_sub_duration_heartbeat(ost, pkt);
-        if (ret < 0) {
-            av_log(NULL, AV_LOG_ERROR,
-                   "Subtitle heartbeat logic failed in %s! (%s)\n",
-                   __func__, av_err2str(ret));
-            exit_program(1);
-        }
-    }
-
-    of_output_packet(of, opkt, ost, 0);
-
-    ost->streamcopy_started = 1;
-}
-
 static void check_decode_result(InputStream *ist, int *got_output, int ret)
 {
     if (*got_output || ret<0)
@@ -1847,7 +1768,7 @@ static int process_input_packet(InputStream *ist, const AVPacket *pkt, int no_eo
             continue;
         }
 
-        do_streamcopy(ist, ost, pkt, ist->dts);
+        of_streamcopy(ist, ost, pkt, ist->dts);
     }
 
     return !eof_reached;
diff --git a/fftools/ffmpeg.h b/fftools/ffmpeg.h
index 8ec0f1b3f3..46b4614ec4 100644
--- a/fftools/ffmpeg.h
+++ b/fftools/ffmpeg.h
@@ -872,6 +872,13 @@ void of_enc_stats_close(void);
  * must be supplied in this case.
  */
 void of_output_packet(OutputFile *of, AVPacket *pkt, OutputStream *ost, int eof);
+
+/**
+ * @param dts predicted packet dts in AV_TIME_BASE_Q
+ */
+void of_streamcopy(InputStream *ist, OutputStream *ost,
+                   const AVPacket *pkt, int64_t dts);
+
 int64_t of_filesize(OutputFile *of);
 
 int ifile_open(const OptionsContext *o, const char *filename);
diff --git a/fftools/ffmpeg_mux.c b/fftools/ffmpeg_mux.c
index 40b439eea2..96ed50f73c 100644
--- a/fftools/ffmpeg_mux.c
+++ b/fftools/ffmpeg_mux.c
@@ -378,6 +378,82 @@ fail:
 
 }
 
+void of_streamcopy(InputStream *ist, OutputStream *ost,
+                   const AVPacket *pkt, int64_t dts)
+{
+    OutputFile *of = output_files[ost->file_index];
+    int64_t start_time = (of->start_time == AV_NOPTS_VALUE) ? 0 : of->start_time;
+    int64_t ost_tb_start_time = av_rescale_q(start_time, AV_TIME_BASE_Q, ost->mux_timebase);
+    AVPacket *opkt = ost->pkt;
+
+    av_packet_unref(opkt);
+    // EOF: flush output bitstream filters.
+    if (!pkt) {
+        of_output_packet(of, opkt, ost, 1);
+        return;
+    }
+
+    if (!ost->streamcopy_started && !(pkt->flags & AV_PKT_FLAG_KEY) &&
+        !ost->copy_initial_nonkeyframes)
+        return;
+
+    if (!ost->streamcopy_started) {
+        if (!ost->copy_prior_start &&
+            (pkt->pts == AV_NOPTS_VALUE ?
+             dts < ost->ts_copy_start :
+             pkt->pts < av_rescale_q(ost->ts_copy_start, AV_TIME_BASE_Q, pkt->time_base)))
+            return;
+
+        if (of->start_time != AV_NOPTS_VALUE && dts < of->start_time)
+            return;
+    }
+
+    if (of->recording_time != INT64_MAX &&
+        dts >= of->recording_time + start_time) {
+        close_output_stream(ost);
+        return;
+    }
+
+    if (av_packet_ref(opkt, pkt) < 0)
+        exit_program(1);
+
+    opkt->time_base = ost->mux_timebase;
+
+    if (pkt->pts != AV_NOPTS_VALUE)
+        opkt->pts = av_rescale_q(pkt->pts, pkt->time_base, opkt->time_base) - ost_tb_start_time;
+
+    if (pkt->dts == AV_NOPTS_VALUE) {
+        opkt->dts = av_rescale_q(dts, AV_TIME_BASE_Q, opkt->time_base);
+    } else if (ost->st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) {
+        int duration = av_get_audio_frame_duration2(ist->par, pkt->size);
+        if(!duration)
+            duration = ist->par->frame_size;
+        opkt->dts = av_rescale_delta(pkt->time_base, pkt->dts,
+                                    (AVRational){1, ist->par->sample_rate}, duration,
+                                    &ist->filter_in_rescale_delta_last, opkt->time_base);
+        /* dts will be set immediately afterwards to what pts is now */
+        opkt->pts = opkt->dts - ost_tb_start_time;
+    } else
+        opkt->dts = av_rescale_q(pkt->dts, pkt->time_base, opkt->time_base);
+    opkt->dts -= ost_tb_start_time;
+
+    opkt->duration = av_rescale_q(pkt->duration, pkt->time_base, opkt->time_base);
+
+    {
+        int ret = trigger_fix_sub_duration_heartbeat(ost, pkt);
+        if (ret < 0) {
+            av_log(NULL, AV_LOG_ERROR,
+                   "Subtitle heartbeat logic failed in %s! (%s)\n",
+                   __func__, av_err2str(ret));
+            exit_program(1);
+        }
+    }
+
+    of_output_packet(of, opkt, ost, 0);
+
+    ost->streamcopy_started = 1;
+}
+
 static int thread_stop(Muxer *mux)
 {
     void *ret;