From acbafeaeb7926af495a9c375903b0c190af6af88 Mon Sep 17 00:00:00 2001
From: Gabriel Hege <g+ffmpeg@hege.cc>
Date: Wed, 16 Apr 2025 13:51:06 +0200
Subject: [PATCH] fix VVC encoding with leading pictures

The default behavior for VVenC (since v1.10.0) is to create an IDR with
leading pictures for the first picture in decoding order (POC 32). This
leads to FFmpeg generating an edit list with an empty entry, skipping
the leading pictures.

This patch fixes the calculation for the start_pts, while the DTS is
negative (as produced by vvenc).

Signed-off-by: Gabriel Hege <g+ffmpeg@hege.cc>
---
 libavformat/movenc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index 4bc8bd1b2a..305f920022 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -3966,7 +3966,7 @@ static int mov_write_edts_tag(AVIOContext *pb, MOVMuxContext *mov,
     int flags = 0;
 
     if (track->entry) {
-        if (start_dts != track->cluster[0].dts || start_ct != track->cluster[0].cts) {
+        if (start_dts != track->cluster[0].dts || (start_ct != track->cluster[0].cts && track->cluster[0].dts >= 0)) {
 
             av_log(mov->fc, AV_LOG_DEBUG,
                    "EDTS using dts:%"PRId64" cts:%d instead of dts:%"PRId64" cts:%"PRId64" tid:%d\n",
@@ -6928,7 +6928,7 @@ int ff_mov_write_packet(AVFormatContext *s, AVPacket *pkt)
         trk->flags |= MOV_TRACK_CTTS;
     trk->cluster[trk->entry].cts   = pkt->pts - pkt->dts;
     trk->cluster[trk->entry].flags = 0;
-    if (trk->start_cts == AV_NOPTS_VALUE)
+    if (trk->start_cts == AV_NOPTS_VALUE || (pkt->dts <= 0 && trk->start_cts > pkt->pts - pkt->dts))
         trk->start_cts = pkt->pts - pkt->dts;
     if (trk->end_pts == AV_NOPTS_VALUE)
         trk->end_pts = trk->cluster[trk->entry].dts +
-- 
2.43.0