Crash in decode_nal_units

[astrange]

Someone sent me a crash log that crashes here:

 http://trac.perian.org/browser/ffmpeg/libavcodec/h264.c#L3764

astrange@~> gdb
GNU gdb 6.3.50-20050815 (Apple version gdb-1708) (Thu Nov  3 21:59:02 UTC 2011)
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This GDB was configured as "x86_64-apple-darwin".
(gdb) set sharedlibrary preload-libraries off(gdb) file /Users/astrange/perian/Perian\ 1.2.3\ dSYM/Perian.component/Contents/MacOS/Perian
Reading symbols from /Users/astrange/perian/Perian 1.2.3 dSYM/Perian.component/Contents/MacOS/Perian...Reading symbols from /Users/astrange/perian/Perian 1.2.3 dSYM/Perian.component.dSYM/Contents/Resources/DWARF/Perian...done.
done.
(gdb) p/x 0x07bf943d - 0x7b32000$1 = 0xc743d
(gdb) info line *$1Line 2656 of "/Users/astrange/Projects/video/Perian/ffmpeg/libavcodec/h264.c" starts at address 0xc7438 <decode_nal_units+1192> and ends at 0xc7444 <decode_nal_units+1204>.
(gdb) x/i $1
0xc743d <decode_nal_units+1197>:	movzbl (%edx),%eax
(gdb) x/64i $1-32
0xc741d <decode_nal_units+1165>:	add    (%eax),%al
0xc741f <decode_nal_units+1167>:	test   %ebx,%ebx
0xc7421 <decode_nal_units+1169>:	jle    0xc7ac6 <decode_nal_units+2870>
0xc7427 <decode_nal_units+1175>:	mov    0x44(%esp),%eax
0xc742b <decode_nal_units+1179>:	lea    (%esi,%eax,1),%edx
0xc742e <decode_nal_units+1182>:	movl   $0x0,0x60(%esp)
0xc7436 <decode_nal_units+1190>:	xor    %ecx,%ecx
0xc7438 <decode_nal_units+1192>:	shll   $0x8,0x60(%esp)
0xc743d <decode_nal_units+1197>:	movzbl (%edx),%eax
0xc7440 <decode_nal_units+1200>:	or     %eax,0x60(%esp)
0xc7444 <decode_nal_units+1204>:	inc    %ecx
0xc7445 <decode_nal_units+1205>:	inc    %edx
0xc7446 <decode_nal_units+1206>:	cmp    %ebx,%ecx
0xc7448 <decode_nal_units+1208>:	jne    0xc7438 <decode_nal_units+1192>
…