[vlc-commits] [Git][videolan/vlc][master] demux: mkv: fix ProRes header size

[Steve Lhomme (@robUx4)]

Steve Lhomme pushed to branch master at VideoLAN / VLC


Commits:
f0c952e5 by Steve Lhomme at 2026-10-03T11:47:50+00:00
demux: mkv: fix ProRes header size

Since 618a236d93702381f10ca1b0481c3048bdf9a515 we write a size
in the buffer.

But SMPTE RDD 36:2022 [^1] defines the size in the header, before the
frame_identifier "icpf" as:

> The total size of the compressed frame in bytes (including the frame_size
> element itself and, if present, stuffing).

In our case that size size of the Block data + 8.

It also matches matroskadec.c in FFmpeg [^2].

[^1]: https://pub.smpte.org/doc/rdd36/20220909-pub/
[^2]: https://code.ffmpeg.org/FFmpeg/FFmpeg/src/commit/49fb9b44d5eadca5bef123801ddd27407220c074/libavformat/matroskadec.c#L3890

- - - - -


1 changed file:

- modules/demux/mkv/mkv.cpp


Changes:

=====================================
modules/demux/mkv/mkv.cpp
=====================================
@@ -638,7 +638,7 @@ static void BlockDecode( demux_t *p_demux, KaxBlock *block, KaxSimpleBlock *simp
         }
         if ( track.fmt.i_codec == VLC_CODEC_PRORES )
         {
-            SetDWBE( p_block->p_buffer, p_block->i_buffer - 8);
+            SetDWBE( p_block->p_buffer, p_block->i_buffer + 8);
             memcpy( p_block->p_buffer + 4, "icpf", 4 );
         }
 



View it on GitLab: https://code.videolan.org/videolan/vlc/-/commit/f0c952e5709512ff1354f7d1ab511b57f0cf9d28

-- 
View it on GitLab: https://code.videolan.org/videolan/vlc/-/commit/f0c952e5709512ff1354f7d1ab511b57f0cf9d28
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