From 81bc7bc52e27d592c00fb4ed39a448d18d4d42db Mon Sep 17 00:00:00 2001
From: Wang Yaqiang <wangyaqiang03@kuaishou.com>
Date: Thu, 9 Mar 2023 17:29:12 +0800
Subject: [PATCH] avformat/img2dec: fix unable to find svg format when the svg
 resources start with "<svg" or "<!--"

svg is xml, but <?xml is not required,
it can start with <svg and can have multiple empty lines,
or start with <!-- include some comments,
but must first line if start with <?xml.

Signed-off-by: Wang Yaqiang <wangyaqiang03@kuaishou.com>
Signed-off-by: Marton Balint <cus@passwd.hu>
---
 libavformat/img2dec.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/libavformat/img2dec.c b/libavformat/img2dec.c
index 5a63d7c81d..c037b6aa88 100644
--- a/libavformat/img2dec.c
+++ b/libavformat/img2dec.c
@@ -964,8 +964,13 @@ static int svg_probe(const AVProbeData *p)
 {
     const uint8_t *b = p->buf;
     const uint8_t *end = p->buf + p->buf_size;
-
-    if (memcmp(p->buf, "<?xml", 5))
+    while (b < end && av_isspace(*b))
+        b++;
+    if (b >= end - 5)
+        return 0;
+    if (!memcmp(b, "<svg", 4))
+        return AVPROBE_SCORE_EXTENSION + 1;
+    if (memcmp(p->buf, "<?xml", 5) && memcmp(b, "<!--", 4))
         return 0;
     while (b < end) {
         int inc = ff_subtitles_next_line(b);