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h265parse: Ensure parsing ends on start-code + full header

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The parser is used all over the place assuming that after calling
gst_h265_parser_identify_nalu(), the start-code found is can also be
identified. In H264 this works, because scan_for_start_code rely on
gst_byte_reader_masked_scan_uint32() that ensures that 1 byte passed the 3
bytes start code is found. But for HEVC, we need two bytes to identify the
following NAL.

This patch will return NO_NAL_END, even if a start code is found in the case
there was not enough bytes. This solution was chosen to maintain backward
compatibility, and reduce complexicity.

Fixes #1287

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/1251>
This commit is contained in:
Nicolas Dufresne 2020-05-07 13:59:33 -04:00
parent 26296646d7
commit 90ca8850de
1 changed files with 9 additions and 0 deletions
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9
gst-libs/gst/codecparsers/gsth265parser.c
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@ -1484,6 +1484,15 @@ gst_h265_parser_identify_nalu (GstH265Parser * parser,
return GST_H265_PARSER_NO_NAL_END;
}
/* Callers assumes that enough data will available to identify the next NAL,
* but scan_for_start_codes() only ensure 1 extra byte is available. Ensure
* we have the required two header bytes (3 bytes start code and 2 byte
* header). */
if (size - (nalu->offset + off2) < 5) {
GST_DEBUG ("Not enough bytes identify the next NAL.");
return GST_H265_PARSER_NO_NAL_END;
}
/* Mini performance improvement:
* We could have a way to store how many 0s were skipped to avoid
* parsing them again on the next NAL */