diff --git a/libavformat/internal.h b/libavformat/internal.h
index da64c641a7..9d614fb12c 100644
--- a/libavformat/internal.h
+++ b/libavformat/internal.h
@@ -657,14 +657,13 @@ int ff_bprint_to_codecpar_extradata(AVCodecParameters *par, struct AVBPrint *buf
 
 /**
  * Find the next packet in the interleaving queue for the given stream.
- * The packet is not removed from the interleaving queue, but only
- * a pointer to it is returned.
+ * The pkt parameter is filled in with the queued packet, including
+ * references to the data (which the caller is not allowed to keep or
+ * modify).
  *
- * @param ts_offset the ts difference between packet in the queue and the muxer.
- *
- * @return a pointer to the next packet, or NULL if no packet is queued
- *         for this stream.
+ * @return 0 if a packet was found, a negative value if no packet was found
  */
-const AVPacket *ff_interleaved_peek(AVFormatContext *s, int stream, int64_t *ts_offset);
+int ff_interleaved_peek(AVFormatContext *s, int stream,
+                        AVPacket *pkt, int add_offset);
 
 #endif /* AVFORMAT_INTERNAL_H */
diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index efa050ee44..7a726c6bfd 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -4484,15 +4484,13 @@ static int mov_flush_fragment(AVFormatContext *s, int force)
     for (i = 0; i < s->nb_streams; i++) {
         MOVTrack *track = &mov->tracks[i];
         if (!track->end_reliable) {
-            int64_t ts_offset;
-            const AVPacket *next = ff_interleaved_peek(s, i, &ts_offset);
-            if (next) {
-                track->track_duration = next->dts - track->start_dts + ts_offset;
-                if (next->pts != AV_NOPTS_VALUE)
-                    track->end_pts = next->pts;
+            AVPacket pkt;
+            if (!ff_interleaved_peek(s, i, &pkt, 1)) {
+                track->track_duration = pkt.dts - track->start_dts;
+                if (pkt.pts != AV_NOPTS_VALUE)
+                    track->end_pts = pkt.pts;
                 else
-                    track->end_pts = next->dts;
-                track->end_pts += ts_offset;
+                    track->end_pts = pkt.dts;
             }
         }
     }
diff --git a/libavformat/mux.c b/libavformat/mux.c
index 77823a4e75..4d47ddcbde 100644
--- a/libavformat/mux.c
+++ b/libavformat/mux.c
@@ -692,6 +692,8 @@ static int write_packet(AVFormatContext *s, AVPacket *pkt)
     pts_backup = pkt->pts;
     dts_backup = pkt->dts;
 
+    // If the timestamp offsetting below is adjusted, adjust
+    // ff_interleaved_peek similarly.
     if (s->output_ts_offset) {
         AVStream *st = s->streams[pkt->stream_index];
         int64_t offset = av_rescale_q(s->output_ts_offset, AV_TIME_BASE_Q, st->time_base);
@@ -1180,23 +1182,30 @@ int ff_interleave_packet_per_dts(AVFormatContext *s, AVPacket *out,
     }
 }
 
-const AVPacket *ff_interleaved_peek(AVFormatContext *s, int stream, int64_t *ts_offset)
+int ff_interleaved_peek(AVFormatContext *s, int stream,
+                        AVPacket *pkt, int add_offset)
 {
     AVPacketList *pktl = s->internal->packet_buffer;
     while (pktl) {
         if (pktl->pkt.stream_index == stream) {
-            AVPacket *pkt = &pktl->pkt;
-            AVStream *st = s->streams[pkt->stream_index];
-            *ts_offset = st->mux_ts_offset;
-
-            if (s->output_ts_offset)
-                *ts_offset += av_rescale_q(s->output_ts_offset, AV_TIME_BASE_Q, st->time_base);
-
-            return pkt;
+            *pkt = pktl->pkt;
+            if (add_offset) {
+                AVStream *st = s->streams[pkt->stream_index];
+                int64_t offset = st->mux_ts_offset;
+
+                if (s->output_ts_offset)
+                    offset += av_rescale_q(s->output_ts_offset, AV_TIME_BASE_Q, st->time_base);
+
+                if (pkt->dts != AV_NOPTS_VALUE)
+                    pkt->dts += offset;
+                if (pkt->pts != AV_NOPTS_VALUE)
+                    pkt->pts += offset;
+            }
+            return 0;
         }
         pktl = pktl->next;
     }
-    return NULL;
+    return AVERROR(ENOENT);
 }
 
 /**