diff --git a/doc/snow.txt b/doc/snow.txt index d2945f2292..f99133971c 100644 --- a/doc/snow.txt +++ b/doc/snow.txt @@ -1,18 +1,18 @@ ============================================= -SNOW Video Codec Specification Draft 20080110 +Snow Video Codec Specification Draft 20080110 ============================================= Introduction: ============= -This specification describes the SNOW bitstream syntax and semantics as -well as the formal SNOW decoding process. +This specification describes the Snow bitstream syntax and semantics as +well as the formal Snow decoding process. The decoding process is described precisely and any compliant decoder -MUST produce the exact same output for a spec-conformant SNOW stream. +MUST produce the exact same output for a spec-conformant Snow stream. For encoding, though, any process which generates a stream compliant to the syntactical and semantic requirements and which is decodable by the process described in this spec shall be considered a conformant -SNOW encoder. +Snow encoder. Definitions: ============ @@ -315,7 +315,7 @@ Binary Range Coder: The implemented range coder is an adapted version based upon "Range encoding: an algorithm for removing redundancy from a digitised message." by G. N. N. Martin. -The symbols encoded by the snow range coder are bits (0|1). The +The symbols encoded by the Snow range coder are bits (0|1). The associated probabilities are not fix but change depending on the symbol mix seen so far. @@ -486,7 +486,7 @@ the remaining points shall be bilinearly interpolated from the up to 4 surrounding halfpel and fullpel points, again rounding should be to nearest and halfway values rounded up -compliant snow decoders MUST support 1-1/8 pel luma and 1/2-1/16 pel chroma +compliant Snow decoders MUST support 1-1/8 pel luma and 1/2-1/16 pel chroma interpolation at least @@ -562,7 +562,7 @@ s[w ] shall be considered equivalent to s[w-2] | + | + | + | + +1/2 -snows 9/7 Integer filter: +Snow's 9/7 Integer filter: 1. s[i] -= (3*(s[i-1] + s[i+1]) + 4)>>3; for all even i < w 2. s[i] -= s[i-1] + s[i+1] ; for all odd i < w 3. s[i] += ( s[i-1] + s[i+1] + 4*s[i] + 8)>>4; for all even i < w