From 78812cd147fa2ab1f0aa3019886c0abe00b7c63a Mon Sep 17 00:00:00 2001 From: Mattias Wadman Date: Tue, 13 Feb 2024 11:17:46 +0100 Subject: [PATCH] avcodec/h2645_parse: Don't treat 0x000002 as a start code and truncate MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit According to ITU-T H.265 7.4.2.1 this byte sequence should not appear in a NAL unit but in practice in rare cases it seems it does, possibly due to buggy encoders. Other players like VLC and Quicktime seem to be fine with it. Currently when this sequence is found it is treated as if the next start code has been found and the NAL unit gets truncated. This change limits the code to only look for first start code 0x0000001 or first escape 0x000003. Sadly i can't share the original source file with the issue but the first 80 bytes of the NAL unit looks like this: │00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f│0123456789abcdef│ 0x00000│00 00 00 01 02 01 d0 bc 57 a1 b8 44 70 01 00 0b│........W..Dp...│ 0x00010│80 2e 00 c2 6c ec 3e b9 e3 03 fb 91 2e d2 43 cb│....l.>.......C.│ 0x00020│1d 2c 00 00 02 00 02 00 5c 93 72 6f 31 76 18 00│.,......\.ro1v..│ 0x00030│08 38 aa b1 4c 33 3f fd 08 cb 77 9b d4 3c db 02│.8..L3?...w..<..│ 0x00040│a2 04 73 15 75 de 3b c4 67 c0 8f ca ad 31 f1 99│..s.u.;.g....1..│ Signed-off-by: Anton Khirnov --- libavcodec/h2645_parse.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/libavcodec/h2645_parse.c b/libavcodec/h2645_parse.c index 28db465059..9f66f079c2 100644 --- a/libavcodec/h2645_parse.c +++ b/libavcodec/h2645_parse.c @@ -40,8 +40,9 @@ int ff_h2645_extract_rbsp(const uint8_t *src, int length, nal->skipped_bytes = 0; #define STARTCODE_TEST \ - if (i + 2 < length && src[i + 1] == 0 && src[i + 2] <= 3) { \ - if (src[i + 2] != 3 && src[i + 2] != 0) { \ + if (i + 2 < length && src[i + 1] == 0 && \ + (src[i + 2] == 3 || src[i + 2] == 1)) { \ + if (src[i + 2] == 1) { \ /* startcode, so we must be past the end */ \ length = i; \ } \