From 500caaeda74dd9c660279036293f4b2997cf0b03 Mon Sep 17 00:00:00 2001 From: Dimitri Sokolyuk Date: Sat, 9 Sep 2017 09:42:37 +0200 Subject: Add vendor --- vendor/golang.org/x/image/vp8/quant.go | 98 ++++++++++++++++++++++++++++++++++ 1 file changed, 98 insertions(+) create mode 100644 vendor/golang.org/x/image/vp8/quant.go (limited to 'vendor/golang.org/x/image/vp8/quant.go') diff --git a/vendor/golang.org/x/image/vp8/quant.go b/vendor/golang.org/x/image/vp8/quant.go new file mode 100644 index 0000000..da43616 --- /dev/null +++ b/vendor/golang.org/x/image/vp8/quant.go @@ -0,0 +1,98 @@ +// Copyright 2011 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package vp8 + +// This file implements parsing the quantization factors. + +// quant are DC/AC quantization factors. +type quant struct { + y1 [2]uint16 + y2 [2]uint16 + uv [2]uint16 +} + +// clip clips x to the range [min, max] inclusive. +func clip(x, min, max int32) int32 { + if x < min { + return min + } + if x > max { + return max + } + return x +} + +// parseQuant parses the quantization factors, as specified in section 9.6. +func (d *Decoder) parseQuant() { + baseQ0 := d.fp.readUint(uniformProb, 7) + dqy1DC := d.fp.readOptionalInt(uniformProb, 4) + const dqy1AC = 0 + dqy2DC := d.fp.readOptionalInt(uniformProb, 4) + dqy2AC := d.fp.readOptionalInt(uniformProb, 4) + dquvDC := d.fp.readOptionalInt(uniformProb, 4) + dquvAC := d.fp.readOptionalInt(uniformProb, 4) + for i := 0; i < nSegment; i++ { + q := int32(baseQ0) + if d.segmentHeader.useSegment { + if d.segmentHeader.relativeDelta { + q += int32(d.segmentHeader.quantizer[i]) + } else { + q = int32(d.segmentHeader.quantizer[i]) + } + } + d.quant[i].y1[0] = dequantTableDC[clip(q+dqy1DC, 0, 127)] + d.quant[i].y1[1] = dequantTableAC[clip(q+dqy1AC, 0, 127)] + d.quant[i].y2[0] = dequantTableDC[clip(q+dqy2DC, 0, 127)] * 2 + d.quant[i].y2[1] = dequantTableAC[clip(q+dqy2AC, 0, 127)] * 155 / 100 + if d.quant[i].y2[1] < 8 { + d.quant[i].y2[1] = 8 + } + // The 117 is not a typo. The dequant_init function in the spec's Reference + // Decoder Source Code (http://tools.ietf.org/html/rfc6386#section-9.6 Page 145) + // says to clamp the LHS value at 132, which is equal to dequantTableDC[117]. + d.quant[i].uv[0] = dequantTableDC[clip(q+dquvDC, 0, 117)] + d.quant[i].uv[1] = dequantTableAC[clip(q+dquvAC, 0, 127)] + } +} + +// The dequantization tables are specified in section 14.1. +var ( + dequantTableDC = [128]uint16{ + 4, 5, 6, 7, 8, 9, 10, 10, + 11, 12, 13, 14, 15, 16, 17, 17, + 18, 19, 20, 20, 21, 21, 22, 22, + 23, 23, 24, 25, 25, 26, 27, 28, + 29, 30, 31, 32, 33, 34, 35, 36, + 37, 37, 38, 39, 40, 41, 42, 43, + 44, 45, 46, 46, 47, 48, 49, 50, + 51, 52, 53, 54, 55, 56, 57, 58, + 59, 60, 61, 62, 63, 64, 65, 66, + 67, 68, 69, 70, 71, 72, 73, 74, + 75, 76, 76, 77, 78, 79, 80, 81, + 82, 83, 84, 85, 86, 87, 88, 89, + 91, 93, 95, 96, 98, 100, 101, 102, + 104, 106, 108, 110, 112, 114, 116, 118, + 122, 124, 126, 128, 130, 132, 134, 136, + 138, 140, 143, 145, 148, 151, 154, 157, + } + dequantTableAC = [128]uint16{ + 4, 5, 6, 7, 8, 9, 10, 11, + 12, 13, 14, 15, 16, 17, 18, 19, + 20, 21, 22, 23, 24, 25, 26, 27, + 28, 29, 30, 31, 32, 33, 34, 35, + 36, 37, 38, 39, 40, 41, 42, 43, + 44, 45, 46, 47, 48, 49, 50, 51, + 52, 53, 54, 55, 56, 57, 58, 60, + 62, 64, 66, 68, 70, 72, 74, 76, + 78, 80, 82, 84, 86, 88, 90, 92, + 94, 96, 98, 100, 102, 104, 106, 108, + 110, 112, 114, 116, 119, 122, 125, 128, + 131, 134, 137, 140, 143, 146, 149, 152, + 155, 158, 161, 164, 167, 170, 173, 177, + 181, 185, 189, 193, 197, 201, 205, 209, + 213, 217, 221, 225, 229, 234, 239, 245, + 249, 254, 259, 264, 269, 274, 279, 284, + } +) -- cgit v1.2.3