[FFmpeg-devel] [PATCH] movenc: ensure chapters track extradata is not null and populated (PR #20315)

[Damiano Galassi via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

PR #20315 opened by Damiano Galassi (galad)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20315
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20315.patch

Fix a regression introduced in 4eca8df, writing chapters failed if chapters where not available before mov_write_header() is called, so the chapter track is written in mov_write_trailer(), unfortunately the new track->extradata and track->extradata_size were NULL.

I don't know if this can be reproduced with the FFmpeg cli, but I noticed it when updating HandBrake to FFmpeg 8.


From 649faf2040623d077cbd7da08ff43cbd46f90efc Mon Sep 17 00:00:00 2001
From: Damiano Galassi <damiog@gmail.com>
Date: Fri, 22 Aug 2025 17:01:26 +0200
Subject: [PATCH] movenc: ensure chapters track extradata is not null and
 populated

fix a regression introduced in 4eca8df,
writing chapters failed if chapters where
not available before mov_write_header().
---
 libavformat/movenc.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index 585a018e35..f0890a9da8 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -7463,6 +7463,12 @@ static int mov_create_chapter_track(AVFormatContext *s, int tracknum)
         return ret;
     memcpy(track->par->extradata, stub_header, sizeof(stub_header));
 
+    if (track->extradata == NULL) {
+        track->stsd_count     = 1;
+        track->extradata      = av_calloc(1, sizeof(*track->extradata));
+        track->extradata_size = av_calloc(1, sizeof(*track->extradata_size));
+    }
+
     track->extradata[0] = av_memdup(stub_header, sizeof(stub_header));
     if (!track->extradata[0])
         return AVERROR(ENOMEM);
-- 
2.49.1

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