mirror of
https://github.com/superseriousbusiness/gotosocial
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1a3f26fb5c
* media: add webp support Signed-off-by: Sigrid Solveig Haflínudóttir <sigrid@ftrv.se> * bump exif-terminator to v0.5.0 Signed-off-by: Sigrid Solveig Haflínudóttir <sigrid@ftrv.se> Signed-off-by: Sigrid Solveig Haflínudóttir <sigrid@ftrv.se>
99 lines
3.0 KiB
Go
99 lines
3.0 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package vp8
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// This file implements parsing the quantization factors.
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// quant are DC/AC quantization factors.
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type quant struct {
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y1 [2]uint16
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y2 [2]uint16
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uv [2]uint16
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}
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// clip clips x to the range [min, max] inclusive.
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func clip(x, min, max int32) int32 {
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if x < min {
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return min
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}
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if x > max {
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return max
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}
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return x
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}
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// parseQuant parses the quantization factors, as specified in section 9.6.
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func (d *Decoder) parseQuant() {
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baseQ0 := d.fp.readUint(uniformProb, 7)
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dqy1DC := d.fp.readOptionalInt(uniformProb, 4)
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const dqy1AC = 0
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dqy2DC := d.fp.readOptionalInt(uniformProb, 4)
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dqy2AC := d.fp.readOptionalInt(uniformProb, 4)
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dquvDC := d.fp.readOptionalInt(uniformProb, 4)
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dquvAC := d.fp.readOptionalInt(uniformProb, 4)
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for i := 0; i < nSegment; i++ {
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q := int32(baseQ0)
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if d.segmentHeader.useSegment {
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if d.segmentHeader.relativeDelta {
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q += int32(d.segmentHeader.quantizer[i])
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} else {
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q = int32(d.segmentHeader.quantizer[i])
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}
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}
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d.quant[i].y1[0] = dequantTableDC[clip(q+dqy1DC, 0, 127)]
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d.quant[i].y1[1] = dequantTableAC[clip(q+dqy1AC, 0, 127)]
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d.quant[i].y2[0] = dequantTableDC[clip(q+dqy2DC, 0, 127)] * 2
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d.quant[i].y2[1] = dequantTableAC[clip(q+dqy2AC, 0, 127)] * 155 / 100
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if d.quant[i].y2[1] < 8 {
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d.quant[i].y2[1] = 8
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}
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// The 117 is not a typo. The dequant_init function in the spec's Reference
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// Decoder Source Code (http://tools.ietf.org/html/rfc6386#section-9.6 Page 145)
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// says to clamp the LHS value at 132, which is equal to dequantTableDC[117].
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d.quant[i].uv[0] = dequantTableDC[clip(q+dquvDC, 0, 117)]
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d.quant[i].uv[1] = dequantTableAC[clip(q+dquvAC, 0, 127)]
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}
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}
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// The dequantization tables are specified in section 14.1.
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var (
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dequantTableDC = [128]uint16{
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4, 5, 6, 7, 8, 9, 10, 10,
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11, 12, 13, 14, 15, 16, 17, 17,
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18, 19, 20, 20, 21, 21, 22, 22,
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23, 23, 24, 25, 25, 26, 27, 28,
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29, 30, 31, 32, 33, 34, 35, 36,
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37, 37, 38, 39, 40, 41, 42, 43,
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44, 45, 46, 46, 47, 48, 49, 50,
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51, 52, 53, 54, 55, 56, 57, 58,
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59, 60, 61, 62, 63, 64, 65, 66,
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67, 68, 69, 70, 71, 72, 73, 74,
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75, 76, 76, 77, 78, 79, 80, 81,
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82, 83, 84, 85, 86, 87, 88, 89,
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91, 93, 95, 96, 98, 100, 101, 102,
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104, 106, 108, 110, 112, 114, 116, 118,
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122, 124, 126, 128, 130, 132, 134, 136,
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138, 140, 143, 145, 148, 151, 154, 157,
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}
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dequantTableAC = [128]uint16{
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4, 5, 6, 7, 8, 9, 10, 11,
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12, 13, 14, 15, 16, 17, 18, 19,
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20, 21, 22, 23, 24, 25, 26, 27,
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28, 29, 30, 31, 32, 33, 34, 35,
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36, 37, 38, 39, 40, 41, 42, 43,
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44, 45, 46, 47, 48, 49, 50, 51,
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52, 53, 54, 55, 56, 57, 58, 60,
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62, 64, 66, 68, 70, 72, 74, 76,
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78, 80, 82, 84, 86, 88, 90, 92,
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94, 96, 98, 100, 102, 104, 106, 108,
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110, 112, 114, 116, 119, 122, 125, 128,
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131, 134, 137, 140, 143, 146, 149, 152,
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155, 158, 161, 164, 167, 170, 173, 177,
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181, 185, 189, 193, 197, 201, 205, 209,
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213, 217, 221, 225, 229, 234, 239, 245,
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249, 254, 259, 264, 269, 274, 279, 284,
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}
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)
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