Caption support (#2462)

Co-authored-by: WithoutPants <53250216+WithoutPants@users.noreply.github.com>

vendor/github.com/asticode/go-astits/data_eit.go

@@ -0,0 +1,124 @@
+package astits
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/asticode/go-astikit"
+)
+
+// EITData represents an EIT data
+// Page: 36 | Chapter: 5.2.4 | Link: https://www.dvb.org/resources/public/standards/a38_dvb-si_specification.pdf
+// (barbashov) the link above can be broken, alternative: https://dvb.org/wp-content/uploads/2019/12/a038_tm1217r37_en300468v1_17_1_-_rev-134_-_si_specification.pdf
+type EITData struct {
+	Events                   []*EITDataEvent
+	LastTableID              uint8
+	OriginalNetworkID        uint16
+	SegmentLastSectionNumber uint8
+	ServiceID                uint16
+	TransportStreamID        uint16
+}
+
+// EITDataEvent represents an EIT data event
+type EITDataEvent struct {
+	Descriptors    []*Descriptor
+	Duration       time.Duration
+	EventID        uint16
+	HasFreeCSAMode bool // When true indicates that access to one or more streams may be controlled by a CA system.
+	RunningStatus  uint8
+	StartTime      time.Time
+}
+
+// parseEITSection parses an EIT section
+func parseEITSection(i *astikit.BytesIterator, offsetSectionsEnd int, tableIDExtension uint16) (d *EITData, err error) {
+	// Create data
+	d = &EITData{ServiceID: tableIDExtension}
+
+	// Get next 2 bytes
+	var bs []byte
+	if bs, err = i.NextBytesNoCopy(2); err != nil {
+		err = fmt.Errorf("astits: fetching next bytes failed: %w", err)
+		return
+	}
+
+	// Transport stream ID
+	d.TransportStreamID = uint16(bs[0])<<8 | uint16(bs[1])
+
+	// Get next 2 bytes
+	if bs, err = i.NextBytesNoCopy(2); err != nil {
+		err = fmt.Errorf("astits: fetching next bytes failed: %w", err)
+		return
+	}
+
+	// Original network ID
+	d.OriginalNetworkID = uint16(bs[0])<<8 | uint16(bs[1])
+
+	// Get next byte
+	var b byte
+	if b, err = i.NextByte(); err != nil {
+		err = fmt.Errorf("astits: fetching next byte failed: %w", err)
+		return
+	}
+
+	// Segment last section number
+	d.SegmentLastSectionNumber = uint8(b)
+
+	// Get next byte
+	if b, err = i.NextByte(); err != nil {
+		err = fmt.Errorf("astits: fetching next byte failed: %w", err)
+		return
+	}
+
+	// Last table ID
+	d.LastTableID = uint8(b)
+
+	// Loop until end of section data is reached
+	for i.Offset() < offsetSectionsEnd {
+		// Get next 2 bytes
+		if bs, err = i.NextBytesNoCopy(2); err != nil {
+			err = fmt.Errorf("astits: fetching next bytes failed: %w", err)
+			return
+		}
+
+		// Event ID
+		var e = &EITDataEvent{}
+		e.EventID = uint16(bs[0])<<8 | uint16(bs[1])
+
+		// Start time
+		if e.StartTime, err = parseDVBTime(i); err != nil {
+			err = fmt.Errorf("astits: parsing DVB time")
+			return
+		}
+
+		// Duration
+		if e.Duration, err = parseDVBDurationSeconds(i); err != nil {
+			err = fmt.Errorf("astits: parsing DVB duration seconds failed: %w", err)
+			return
+		}
+
+		// Get next byte
+		if b, err = i.NextByte(); err != nil {
+			err = fmt.Errorf("astits: fetching next byte failed: %w", err)
+			return
+		}
+
+		// Running status
+		e.RunningStatus = uint8(b) >> 5
+
+		// Free CA mode
+		e.HasFreeCSAMode = uint8(b&0x10) > 0
+
+		// We need to rewind since the current byte is used by the descriptor as well
+		i.Skip(-1)
+
+		// Descriptors
+		if e.Descriptors, err = parseDescriptors(i); err != nil {
+			err = fmt.Errorf("astits: parsing descriptors failed: %w", err)
+			return
+		}
+
+		// Add event
+		d.Events = append(d.Events, e)
+	}
+	return
+}