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package mpeg
// http://www.mpucoder.com/DVD/spu.html
// http://sam.zoy.org/writings/dvd/subtitles/
// TODO: still some unknown data before and after pixel data
import (
"fmt"
"strings"
"github.com/wader/fq/format"
"github.com/wader/fq/pkg/decode"
"github.com/wader/fq/pkg/interp"
"github.com/wader/fq/pkg/scalar"
)
func init() {
interp.RegisterFormat(
format.MPEG_SPU,
&decode.Format{
Description: "Sub Picture Unit (DVD subtitle)",
DecodeFn: spuDecode,
})
}
const (
CMD_END = 0xff
FSTA_DSP = 0x00
STA_DSP = 0x01
STP_DSP = 0x02
SET_COLOR = 0x03
SET_CONTR = 0x04
SET_DAREA = 0x05
SET_DSPXA = 0x06
CHG_COLCON = 0x07
)
var commandNames = scalar.UintMapSymStr{
CMD_END: "CMD_END",
FSTA_DSP: "FSTA_DSP",
STA_DSP: "STA_DSP",
STP_DSP: "STP_DSP",
SET_COLOR: "SET_COLOR",
SET_CONTR: "SET_CONTR",
SET_DAREA: "SET_DAREA",
SET_DSPXA: "SET_DSPXA",
CHG_COLCON: "CHG_COLCON",
}
func rleValue(d *decode.D) (uint64, uint64, int) {
p := uint(d.PeekUintBits(8))
// match zero prefix
switch {
case p&0b1111_1100 == 0:
// 000000nnnnnnnncc
d.U6()
return d.U8(), d.U2(), 16
case p&0b1111_0000 == 0:
// 0000nnnnnncc
d.U4()
return d.U6(), d.U2(), 12
case p&0b1100_0000 == 0:
// 00nnnncc
d.U2()
return d.U4(), d.U2(), 8
default:
// nncc
return d.U2(), d.U2(), 4
}
}
//nolint:unparam
func decodeLines(d *decode.D, lines int, width int) []string {
var ls []string
for i := 0; i < lines; i++ {
l := ""
for x := 0; x < width; {
n, c, b := rleValue(d)
pixel := " "
if c != 0 {
pixel = fmt.Sprintf("%d", c)
}
if n == 0 && b == 16 {
l += strings.Repeat(pixel, width-len(l))
break
}
x += int(n)
}
if d.ByteAlignBits() > 0 {
d.U(d.ByteAlignBits())
}
ls = append(ls, l)
}
return ls
}
func spuDecode(d *decode.D) any {
d.FieldU16("size")
dcsqtOffset := d.FieldU16("dcsqt_offset")
// to catch infinite loops
offsetSeen := map[uint64]struct{}{}
d.SeekAbs(int64(dcsqtOffset) * 8)
d.FieldArray("dcsqt", func(d *decode.D) {
lastDCSQ := false
for !lastDCSQ {
d.FieldStruct("dcsq", func(d *decode.D) {
dcsqStart := uint64(d.Pos() / 8)
d.FieldU16("delay")
offset := d.FieldU16("offset")
if offset == dcsqStart {
lastDCSQ = true
return
}
if _, ok := offsetSeen[offset]; ok {
d.Fatalf("dcsqt loop detected for %d", offset)
}
offsetSeen[offset] = struct{}{}
var pxdTFOffset int64
var pxdBFOffset int64
var width uint64
var height uint64
d.FieldArray("commands", func(d *decode.D) {
seenEnd := false
for !seenEnd {
d.FieldStruct("command", func(d *decode.D) {
cmd := d.FieldU8("type", commandNames)
switch cmd {
case CMD_END:
seenEnd = true
case FSTA_DSP:
// no args
case STA_DSP:
// no args
case STP_DSP:
// no args
case SET_COLOR:
d.FieldU4("a0")
d.FieldU4("a1")
d.FieldU4("a2")
d.FieldU4("a3")
case SET_CONTR:
d.FieldU4("a0")
d.FieldU4("a1")
d.FieldU4("a2")
d.FieldU4("a3")
case SET_DAREA:
startX := d.FieldU12("start_x")
endX := d.FieldU12("end_x")
startY := d.FieldU12("start_y")
endY := d.FieldU12("end_y")
width = endX - startX + 1
height = endY - startY + 1
case SET_DSPXA:
pxdTFOffset = int64(d.FieldU16("offset_top_field")) * 8
pxdBFOffset = int64(d.FieldU16("offset_bottom_field")) * 8
case CHG_COLCON:
size := d.FieldU16("size")
// TODO
d.FieldRawLen("data", int64(size)*8)
default:
d.Fatalf("unknown command %d", cmd)
}
})
}
})
halfHeight := int(height) / 2
// var tLines []string
// var bLines []string
if pxdTFOffset != 0 {
d.SeekAbs(pxdTFOffset)
/*tLines*/ _ = decodeLines(d, halfHeight, int(width))
d.RangeFn(pxdTFOffset, d.Pos()-pxdTFOffset, func(d *decode.D) {
d.FieldRawLen("top_pixels", d.BitsLeft())
})
}
if pxdBFOffset != 0 {
d.SeekAbs(pxdBFOffset)
/*bLines*/ _ = decodeLines(d, halfHeight, int(width))
d.RangeFn(pxdBFOffset, d.Pos()-pxdBFOffset, func(d *decode.D) {
d.FieldRawLen("bottom_pixels", d.BitsLeft())
})
}
// var lines []string
// for i := 0; i < halfHeight; i++ {
// lines = append(lines, tLines[i])
// lines = append(lines, bLines[i])
// }
// for _, l := range lines {
// log.Printf("l: '%s'\n", l)
// }
d.SeekAbs(int64(offset) * 8)
})
}
})
return nil
}
|
