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9b81d4d3ab
Preparation to make decoder use less memory and API more type safe. Now each scalar type has it's own struct type so it can store different things and enables to have a scalar interface. Also own types will enable experimenting with decode DLS designs like using chained methods that are type aware.
72 lines
1.7 KiB
Go
72 lines
1.7 KiB
Go
package vpx
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// https://tools.ietf.org/html/rfc6386
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import (
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"github.com/wader/fq/format"
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"github.com/wader/fq/pkg/decode"
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"github.com/wader/fq/pkg/interp"
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"github.com/wader/fq/pkg/scalar"
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)
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// TODO: vpx frame?
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func init() {
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interp.RegisterFormat(decode.Format{
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Name: format.VP8_FRAME,
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Description: "VP8 frame",
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DecodeFn: vp8Decode,
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})
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}
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func vp8Decode(d *decode.D, _ any) any {
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var isKeyFrame bool
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versions := map[uint64]struct {
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reconstruction string
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loop string
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}{
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0: {"Bicubic", "Normal"},
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1: {"Bilinear", "Simple"},
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2: {"Bilinear", "None"},
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3: {"None", "None"},
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}
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d.FieldStruct("tag", func(d *decode.D) {
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// first_part_size is not contiguous bits
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firstPartSize0 := d.FieldU3("first_part_size0")
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d.FieldU1("show_frame")
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version := d.FieldU3("version")
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keyFrameV := d.FieldBool("frame_type", scalar.BoolMapSymStr{true: "non_key_frame", false: "key_frame"})
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firstPartSize1 := d.FieldU16LE("first_part_size1")
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firstPartSize := firstPartSize0 | firstPartSize1<<3
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d.FieldValueUint("first_part_size", firstPartSize)
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isKeyFrame = !keyFrameV
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if v, ok := versions[version]; ok {
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d.FieldValueStr("reconstruction", v.reconstruction)
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d.FieldValueStr("loop", v.loop)
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}
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})
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if isKeyFrame {
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d.FieldU24("start_code", d.UintValidate(0x9d012a), scalar.UintHex)
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// width and height are not contiguous bits
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width0 := d.FieldU8("width0")
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d.FieldU2("horizontal_scale")
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width1 := d.FieldU6("width1")
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d.FieldValueUint("width", width0|width1<<8)
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height0 := d.FieldU8("height0")
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d.FieldU2("vertical_scale")
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height1 := d.FieldU6("height1")
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d.FieldValueUint("height", height0|height1<<8)
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}
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d.FieldRawLen("data", d.BitsLeft())
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return nil
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}
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