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Add support for open stl subtitles (#33)
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* Add support for open stl subtitles

* Adding STL OPN test and some more metadata

* Updated based on comments

* Moved functions from open_subtitle.go to stl.go

* Updated based on comments
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@arnestorksen
arnestorksen committed Dec 8, 2020
1 parent 058ee0f commit 21f9730
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Showing 6 changed files with 252 additions and 15 deletions.
179 changes: 170 additions & 9 deletions stl.go
View file
Expand Up @@ -3,6 +3,7 @@ package astisub
import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"io"
"math"
Expand Down Expand Up @@ -161,6 +162,14 @@ const (
// TTI Special Extension Block Number
const extensionBlockNumberReservedUserData = 0xfe

const stlLineSeparator = 0x8a

type STLPosition struct {
VerticalPosition int
MaxRows int
Rows int
}

// ReadFromSTL parses an .stl content
func ReadFromSTL(i io.Reader) (o *Subtitles, err error) {
// Init
Expand Down Expand Up @@ -189,10 +198,15 @@ func ReadFromSTL(i io.Reader) (o *Subtitles, err error) {
// Update metadata
// TODO Add more STL fields to metadata
o.Metadata = &Metadata{
Framerate: g.framerate,
Framerate: g.framerate,
STLCountryOfOrigin: g.countryOfOrigin,
STLCreationDate: &g.creationDate,
STLDisplayStandardCode: g.displayStandardCode,
STLMaximumNumberOfDisplayableCharactersInAnyTextRow: astikit.IntPtr(g.maximumNumberOfDisplayableCharactersInAnyTextRow),
STLMaximumNumberOfDisplayableRows: astikit.IntPtr(g.maximumNumberOfDisplayableRows),
STLPublisher: g.publisher,
STLRevisionDate: &g.revisionDate,
STLSubtitleListReferenceCode: g.subtitleListReferenceCode,
Title: g.originalProgramTitle,
}
if v, ok := stlLanguageMapping.Get(g.languageCode); ok {
Expand All @@ -218,15 +232,38 @@ func ReadFromSTL(i io.Reader) (o *Subtitles, err error) {
continue
}

justification := parseSTLJustificationCode(t.justificationCode)
rows := bytes.Split(t.text, []byte{stlLineSeparator})

position := STLPosition{
MaxRows: g.maximumNumberOfDisplayableRows,
Rows: len(rows),
VerticalPosition: t.verticalPosition,
}

styleAttributes := StyleAttributes{
STLJustification: &justification,
STLPosition: &position,
}
styleAttributes.propagateSTLAttributes()

// Create item
var i = &Item{
EndAt: t.timecodeOut - g.timecodeStartOfProgramme,
StartAt: t.timecodeIn - g.timecodeStartOfProgramme,
EndAt: t.timecodeOut - g.timecodeStartOfProgramme,
InlineStyle: &styleAttributes,
StartAt: t.timecodeIn - g.timecodeStartOfProgramme,
}

// Loop through rows
for _, text := range bytes.Split(t.text, []byte{0x8a}) {
parseTeletextRow(i, ch, func() styler { return newSTLStyler() }, text)
for _, text := range bytes.Split(t.text, []byte{stlLineSeparator}) {
if g.displayStandardCode == stlDisplayStandardCodeOpenSubtitling {
err = parseOpenSubtitleRow(i, ch, func() styler { return newSTLStyler() }, text)
if err != nil {
return nil, err
}
} else {
parseTeletextRow(i, ch, func() styler { return newSTLStyler() }, text)
}
}

// Append item
Expand Down Expand Up @@ -302,7 +339,8 @@ func newGSIBlock(s Subtitles) (g *gsiBlock) {
languageCode: stlLanguageCodeFrench,
maximumNumberOfDisplayableCharactersInAnyTextRow: 40,
maximumNumberOfDisplayableRows: 23,
subtitleListReferenceCode: "12345678",
revisionDate: Now(),
subtitleListReferenceCode: "",
timecodeStatus: stlTimecodeStatusIntendedForUse,
totalNumberOfDisks: 1,
totalNumberOfSubtitleGroups: 1,
Expand All @@ -312,6 +350,11 @@ func newGSIBlock(s Subtitles) (g *gsiBlock) {

// Add metadata
if s.Metadata != nil {
if s.Metadata.STLCreationDate != nil {
g.creationDate = *s.Metadata.STLCreationDate
}
g.countryOfOrigin = s.Metadata.STLCountryOfOrigin
g.displayStandardCode = s.Metadata.STLDisplayStandardCode
g.framerate = s.Metadata.Framerate
if v, ok := stlLanguageMapping.GetInverse(s.Metadata.Language); ok {
g.languageCode = v.(string)
Expand All @@ -324,6 +367,10 @@ func newGSIBlock(s Subtitles) (g *gsiBlock) {
g.maximumNumberOfDisplayableRows = *s.Metadata.STLMaximumNumberOfDisplayableRows
}
g.publisher = s.Metadata.STLPublisher
if s.Metadata.STLRevisionDate != nil {
g.revisionDate = *s.Metadata.STLRevisionDate
}
g.subtitleListReferenceCode = s.Metadata.STLSubtitleListReferenceCode
}

// Timecode first in cue
Expand Down Expand Up @@ -598,18 +645,46 @@ func newTTIBlock(i *Item, idx int) (t *ttiBlock) {
subtitleNumber: idx,
timecodeIn: i.StartAt,
timecodeOut: i.EndAt,
verticalPosition: 20,
verticalPosition: stlVerticalPositionFromStyle(i.InlineStyle),
}

// Add text
var lines []string
for _, l := range i.Lines {
lines = append(lines, l.String())
var lineItems []string
for _, li := range l.Items {
lineItems = append(lineItems, li.STLString())
}
lines = append(lines, strings.Join(lineItems, " "))
}
t.text = []byte(strings.Join(lines, "\n"))
t.text = []byte(strings.Join(lines, string(rune(stlLineSeparator))))
return
}

func stlVerticalPositionFromStyle(sa *StyleAttributes) int {
if sa != nil && sa.STLPosition != nil {
return sa.STLPosition.VerticalPosition
} else {
return 20
}
}

func (li LineItem) STLString() string {
rs := li.Text
if li.InlineStyle != nil {
if li.InlineStyle.STLItalics != nil && *li.InlineStyle.STLItalics {
rs = string(rune(0x80)) + rs + string(rune(0x81))
}
if li.InlineStyle.STLUnderline != nil && *li.InlineStyle.STLUnderline {
rs = string(rune(0x82)) + rs + string(rune(0x83))
}
if li.InlineStyle.STLBoxing != nil && *li.InlineStyle.STLBoxing {
rs = string(rune(0x84)) + rs + string(rune(0x85))
}
}
return rs
}

// parseTTIBlock parses a TTI block
func parseTTIBlock(p []byte, framerate int) *ttiBlock {
return &ttiBlock{
Expand Down Expand Up @@ -883,3 +958,89 @@ func encodeTextSTL(i string) (o []byte) {
}
return
}

func parseSTLJustificationCode(i byte) Justification {
switch i {
case 0x00:
return JustificationUnchanged
case 0x01:
return JustificationLeft
case 0x02:
return JustificationCentered
case 0x03:
return JustificationRight
default:
return JustificationUnchanged
}
}

func isTeletextControlCode(i byte) (b bool) {
return i <= 0x1f
}

func parseOpenSubtitleRow(i *Item, d decoder, fs func() styler, row []byte) error {
// Loop through columns
var l = Line{}
var li = LineItem{InlineStyle: &StyleAttributes{}}
var s styler
for _, v := range row {
// Create specific styler
if fs != nil {
s = fs()
}

if isTeletextControlCode(v) {
return errors.New("teletext control code in open text")
}
if s != nil {
s.parseSpacingAttribute(v)
}

// Style has been set
if s != nil && s.hasBeenSet() {
// Style has changed
if s.hasChanged(li.InlineStyle) {
if len(li.Text) > 0 {
// Append line item
appendOpenSubtitleLineItem(&l, li, s)

// Create new line item
sa := &StyleAttributes{}
*sa = *li.InlineStyle
li = LineItem{InlineStyle: sa}
}
s.update(li.InlineStyle)
}
} else {
// Append text
li.Text += string(d.decode(v))
}
}

appendOpenSubtitleLineItem(&l, li, s)

// Append line
if len(l.Items) > 0 {
i.Lines = append(i.Lines, l)
}
return nil
}

func appendOpenSubtitleLineItem(l *Line, li LineItem, s styler) {
// There's some text
if len(strings.TrimSpace(li.Text)) > 0 {
// Make sure inline style exists
if li.InlineStyle == nil {
li.InlineStyle = &StyleAttributes{}
}

// Propagate style attributes
if s != nil {
s.propagateStyleAttributes(li.InlineStyle)
}

// Append line item
li.Text = strings.TrimSpace(li.Text)
l.Items = append(l.Items, li)
}
}
55 changes: 50 additions & 5 deletions stl_test.go
View file
Expand Up @@ -13,17 +13,27 @@ import (

func TestSTL(t *testing.T) {
// Init
astisub.Now = func() (t time.Time) {
t, _ = time.Parse("060102", "170702")
return
}
creationDate, _ := time.Parse("060102", "170702")
revisionDate, _ := time.Parse("060102", "010101")

// Open
s, err := astisub.OpenFile("./testdata/example-in.stl")
assert.NoError(t, err)
assertSubtitleItems(t, s)
// Metadata
assert.Equal(t, &astisub.Metadata{Framerate: 25, Language: astisub.LanguageFrench, STLMaximumNumberOfDisplayableCharactersInAnyTextRow: astikit.IntPtr(40), STLMaximumNumberOfDisplayableRows: astikit.IntPtr(23), STLPublisher: "Copyright test", Title: "Title test"}, s.Metadata)
assert.Equal(t, &astisub.Metadata{
Framerate: 25,
Language: astisub.LanguageFrench,
STLCreationDate: &creationDate,
STLMaximumNumberOfDisplayableCharactersInAnyTextRow: astikit.IntPtr(40),
STLMaximumNumberOfDisplayableRows: astikit.IntPtr(23),
STLPublisher: "Copyright test",
STLDisplayStandardCode: "1",
STLRevisionDate: &revisionDate,
STLSubtitleListReferenceCode: "12345678",
STLCountryOfOrigin: "FRA",
Title: "Title test"},
s.Metadata)

// No subtitles to write
w := &bytes.Buffer{}
Expand All @@ -37,3 +47,38 @@ func TestSTL(t *testing.T) {
assert.NoError(t, err)
assert.Equal(t, string(c), w.String())
}

func TestOPNSTL(t *testing.T) {
// Init
creationDate, _ := time.Parse("060102", "200110")
revisionDate, _ := time.Parse("060102", "200110")

// Open
s, err := astisub.OpenFile("./testdata/example-opn-in.stl")
assert.NoError(t, err)
// Metadata
assert.Equal(t, &astisub.Metadata{
Framerate: 25,
Language: astisub.LanguageEnglish,
STLCountryOfOrigin: "NOR",
STLCreationDate: &creationDate,
STLDisplayStandardCode: "0",
STLMaximumNumberOfDisplayableCharactersInAnyTextRow: astikit.IntPtr(38),
STLMaximumNumberOfDisplayableRows: astikit.IntPtr(11),
STLPublisher: "",
STLRevisionDate: &revisionDate,
Title: ""},
s.Metadata)

// No subtitles to write
w := &bytes.Buffer{}
err = astisub.Subtitles{}.WriteToSTL(w)
assert.EqualError(t, err, astisub.ErrNoSubtitlesToWrite.Error())

// Write
c, err := ioutil.ReadFile("./testdata/example-opn-out.stl")
assert.NoError(t, err)
err = s.WriteToSTL(w)
assert.NoError(t, err)
assert.Equal(t, string(c), w.String())
}
17 changes: 17 additions & 0 deletions subtitles.go
View file
Expand Up @@ -158,6 +158,15 @@ func (c *Color) TTMLString() string {
return fmt.Sprintf("%.6x", uint32(c.Red)<<16|uint32(c.Green)<<8|uint32(c.Blue))
}

type Justification int

var (
JustificationUnchanged = Justification(1)
JustificationLeft = Justification(2)
JustificationCentered = Justification(3)
JustificationRight = Justification(4)
)

// StyleAttributes represents style attributes
type StyleAttributes struct {
SSAAlignment *int
Expand Down Expand Up @@ -188,6 +197,8 @@ type StyleAttributes struct {
SSAUnderline *bool
STLBoxing *bool
STLItalics *bool
STLJustification *Justification
STLPosition *STLPosition
STLUnderline *bool
TeletextColor *Color
TeletextDoubleHeight *bool
Expand Down Expand Up @@ -221,6 +232,7 @@ type StyleAttributes struct {
TTMLWritingMode string
TTMLZIndex int
WebVTTAlign string
WebVTTItalics bool
WebVTTLine string
WebVTTLines int
WebVTTPosition string
Expand Down Expand Up @@ -265,9 +277,14 @@ type Metadata struct {
SSATimer *float64
SSAUpdateDetails string
SSAWrapStyle string
STLCountryOfOrigin string
STLCreationDate *time.Time
STLDisplayStandardCode string
STLMaximumNumberOfDisplayableCharactersInAnyTextRow *int
STLMaximumNumberOfDisplayableRows *int
STLPublisher string
STLRevisionDate *time.Time
STLSubtitleListReferenceCode string
Title string
TTMLCopyright string
}
Expand Down
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Binary file added testdata/example-opn-out.stl
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