RFC Errata
RFC 6386, "VP8 Data Format and Decoding Guide", November 2011
Source of RFC: INDEPENDENT
Errata ID: 5534
Status: Reported
Type: Technical
Publication Format(s) : TEXT
Reported By: Ard Oerlemans
Date Reported: 2018-10-18
Section 19.1 says:
unsigned char *c = pbi->source; unsigned int tmp; tmp = (c[2] << 16) | (c[1] << 8) | c[0]; key_frame = tmp & 0x1; version = (tmp >> 1) & 0x7; show_frame = (tmp >> 4) & 0x1; first_part_size = (tmp >> 5) & 0x7FFFF;
It should say:
unsigned char *c = pbi->source; unsigned int tmp; tmp = (c[2] << 16) | (c[1] << 8) | c[0]; key_frame = !(tmp & 0x1); version = (tmp >> 1) & 0x7; show_frame = (tmp >> 4) & 0x1; first_part_size = (tmp >> 5) & 0x7FFFF;
Notes:
In section 9.1, where the frame tag is described, the field for the key frame is defined as "A 1-bit frame type (0 for key frames, 1 for interframes)."
The code block in section 19.1 interprets the bit in the opposite way: 1 for key frames and 0 for interframes.