[FFmpeg-user] buffer underflow - processing VOB files

Bob DeCarlo bobs2002mail at yahoo.com
Wed Aug 8 23:34:11 EEST 2018

 Hi Carl Eugen and Paul,
I dug into the source code and found the line of code causing the problem, referring to commit:

I rolled back this one line of code and the issue went away:

diff --git a/libavcodec/ac3_parser.c b/libavcodec/ac3_parser.cindex f4618bf215..1015245a90 100644--- a/libavcodec/ac3_parser.c+++ b/libavcodec/ac3_parser.c@@ -218,8 +218,8 @@ static int ac3_sync(uint64_t state, AACAC3ParseContext *hdr_info,     else if (hdr_info->codec_id == AV_CODEC_ID_NONE)         hdr_info->codec_id = AV_CODEC_ID_AC3; +    *need_next_header = (hdr.frame_type != EAC3_FRAME_TYPE_AC3_CONVERT);     *new_frame_start  = (hdr.frame_type != EAC3_FRAME_TYPE_DEPENDENT);-    *need_next_header = *new_frame_start || (hdr.frame_type != EAC3_FRAME_TYPE_AC3_CONVERT);     return hdr.frame_size; }

I reviewed the change set of ae9297097696f3d06417a6e8a5368d5f38a6edb4and see support for 16 channel audio was added.  For the legacy case, it looks like functionality should be maintained with the exception of setting "need_next_header".  My rollback likely breaks the new EAC3 but I just want to show what I think is breaking my test case.

My hope is that you will review this change set, and specifically this one line of code, to see if you possibly agree. You may not need to try my sample, the problem may be visible to you in just reviewing the code.

Thanks and Regards,

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