RFC 6386, "VP8 Data Format and Decoding Guide", November 2011

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.

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