Unused definitions

[podborski]

There are 5 definitions in the spec (section 2) that are never used in the spec text:

• Altref
• Block scan
• Golden frame
• Raster scan
• Switch Frame

[wantehchang]

"Switch frame" is referring to the SWITCH_FRAME value (3) of the frame_type syntax element in the uncompressed_header( ). "Altref" and "golden frame" are similarly referring to reference frame types, although AV1 has two types of "altref": ALTREF_FRAME and ALTREF2_FRAME.

Re: raster scan: it seems that "raster order" is used in the main body of the spec.