[h264parse] [codecparsers] warning observed when parsing some H.264 SEI NALs when payload contains emulation_prevention_three_byte

Submitted by Ursula Maplehurst

Description

Created attachment 342549
Patch

I had been seeing the following warning from h264parse when parsing an H.264 stream with some application-specific SEI NALs:

W GStreamer+codecparsers_h264: 17:21:32.788894716 0xb9567db0 gsth264parser.c:1212:gst_h264_parser_parse_sei_message error parsing "Sei message"
W GStreamer+h264parse: 17:21:32.788945174 0xb9567db0 gsth264parse.c:524:gst_h264_parse_process_sei:<h264parse0> failed to parse one or more SEI message

Upon further investigation, it looks like certain SEI NALs were causing nal_reader_read to eat up some 0x03 bytes which are not actually emulation prevention bytes. Patch for the issue attached.

Cheers,
Ursula

Patch 342549, "Patch":
codecparsers-nalutils.patch

Version: 1.10.2