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mirror of https://github.com/wader/fq.git synced 2024-12-23 13:22:58 +03:00
fq/format/vpx/vp8_frame.go
Mattias Wadman 9b81d4d3ab decode: More type safe API and split scalar into multiple types
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.
2022-12-14 16:23:58 +01:00

72 lines
1.7 KiB
Go

package vpx
// https://tools.ietf.org/html/rfc6386
import (
"github.com/wader/fq/format"
"github.com/wader/fq/pkg/decode"
"github.com/wader/fq/pkg/interp"
"github.com/wader/fq/pkg/scalar"
)
// TODO: vpx frame?
func init() {
interp.RegisterFormat(decode.Format{
Name: format.VP8_FRAME,
Description: "VP8 frame",
DecodeFn: vp8Decode,
})
}
func vp8Decode(d *decode.D, _ any) any {
var isKeyFrame bool
versions := map[uint64]struct {
reconstruction string
loop string
}{
0: {"Bicubic", "Normal"},
1: {"Bilinear", "Simple"},
2: {"Bilinear", "None"},
3: {"None", "None"},
}
d.FieldStruct("tag", func(d *decode.D) {
// first_part_size is not contiguous bits
firstPartSize0 := d.FieldU3("first_part_size0")
d.FieldU1("show_frame")
version := d.FieldU3("version")
keyFrameV := d.FieldBool("frame_type", scalar.BoolMapSymStr{true: "non_key_frame", false: "key_frame"})
firstPartSize1 := d.FieldU16LE("first_part_size1")
firstPartSize := firstPartSize0 | firstPartSize1<<3
d.FieldValueUint("first_part_size", firstPartSize)
isKeyFrame = !keyFrameV
if v, ok := versions[version]; ok {
d.FieldValueStr("reconstruction", v.reconstruction)
d.FieldValueStr("loop", v.loop)
}
})
if isKeyFrame {
d.FieldU24("start_code", d.UintValidate(0x9d012a), scalar.UintHex)
// width and height are not contiguous bits
width0 := d.FieldU8("width0")
d.FieldU2("horizontal_scale")
width1 := d.FieldU6("width1")
d.FieldValueUint("width", width0|width1<<8)
height0 := d.FieldU8("height0")
d.FieldU2("vertical_scale")
height1 := d.FieldU6("height1")
d.FieldValueUint("height", height0|height1<<8)
}
d.FieldRawLen("data", d.BitsLeft())
return nil
}