[FFmpeg-devel] [PATCH v2] avformat/jpegxl_probe: fix incorrect cw_mask and extensions probing

[Leo Izen <leo.izen@gmail.com>]

- Fix incorrectly skipping over the upX_weights
if the cw_mask is present and it is not a multiple of 4.

- Fix not skipping over the extensions payload if an extension
is present.
---
 libavformat/jpegxl_probe.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/libavformat/jpegxl_probe.c b/libavformat/jpegxl_probe.c
index 9cd00da194..b5aac4869b 100644
--- a/libavformat/jpegxl_probe.c
+++ b/libavformat/jpegxl_probe.c
@@ -359,24 +359,31 @@ int ff_jpegxl_verify_codestream_header(const uint8_t *buf, int buflen)
 
         extensions = jxl_u64();
         if (extensions) {
+            uint64_t extensions_len = 0;
             for (int i = 0; i < 64; i++) {
                 if (extensions & (UINT64_C(1) << i))
-                    jxl_u64();
+                    extensions_len += jxl_u64();
             }
+            if (extensions_len)
+                jxl_bits_skip(extensions_len);
         }
     }
 
     /* default transform */
     if (!jxl_bits(1)) {
+        uint32_t cw_mask;
+
         /* opsin inverse matrix */
         if (xyb_encoded && !jxl_bits(1))
             jxl_bits_skip(16 * 16);
+
         /* cw_mask and default weights */
-        if (jxl_bits(1))
+        cw_mask = jxl_bits(3);
+        if (cw_mask & 1)
             jxl_bits_skip(16 * 15);
-        if (jxl_bits(1))
+        if (cw_mask & 2)
             jxl_bits_skip(16 * 55);
-        if (jxl_bits(1))
+        if (cw_mask & 4)
             jxl_bits_skip(16 * 210);
     }
 
-- 
2.36.1

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