fix: make wvttlister worke with Unified Streaming wvtt ismt file

CHANGELOG.md

@@ -7,7 +7,22 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-- Nothing yet
+### Changed
+
+- TfraEntry Time and MoofOffset types changed to unsigned
+- TfraEntr attribute name SampleDelta corrected to SampleNumber
+
+### Added
+
+- MediaSegment and Fragment have new StartPos attribute
+- mp4.File now has Mfra pointer
+- MfraBox has new method FindEntry
+
+### Fixed
+
+- Fragment.GetFullSamples() allows tfdt to be absent
+- Fragment.GetFullSamples() defaults to offset being moof
+- mp4ff-wvttlister works for Unified Streaming wvtt asset
 
 ## [0.38.1] - 2023-09-22
 

cmd/mp4ff-wvttlister/main.go

@@ -5,6 +5,7 @@ import (
 	"bytes"
 	"flag"
 	"fmt"
+	"io"
 	"log"
 	"os"
 	"strings"
@@ -15,7 +16,7 @@ import (
 var usg = `Usage of mp4ff-wvttlister:
 
 mp4ff-wvttlister lists and displays content of wvtt (WebVTT in ISOBMFF) samples.
-Use track with given non-zero track ID or first wvtt track found in an asset.
+Uses track with given non-zero track ID or first wvtt track found in an asset.
 `
 
 var usage = func() {
@@ -49,26 +50,33 @@ func main() {
 		log.Fatalln(err)
 	}
 	defer ifd.Close()
-	parsedMp4, err := mp4.DecodeFile(ifd)
+
+	err = run(ifd, os.Stdout, *trackID, *maxNrSamples)
 	if err != nil {
 		log.Fatal(err)
 	}
+}
+
+func run(ifd io.ReadSeeker, w io.Writer, trackID, maxNrSamples int) error {
+	parsedMp4, err := mp4.DecodeFile(ifd, mp4.WithDecodeFlags(mp4.DecISMFlag))
+	if err != nil {
+		return err
+	}
 
 	if !parsedMp4.IsFragmented() { // Progressive file
-		err = parseProgressiveMp4(parsedMp4, uint32(*trackID), *maxNrSamples)
+		err = parseProgressiveMp4(parsedMp4, w, uint32(trackID), maxNrSamples)
 		if err != nil {
-			fmt.Printf("Error: %s\n", err)
-			os.Exit(1)
+			return err
 		}
-		return
+		return nil
 	}
 
 	// Fragmented file
-	err = parseFragmentedMp4(parsedMp4, uint32(*trackID), *maxNrSamples)
+	err = parseFragmentedMp4(parsedMp4, w, uint32(trackID), maxNrSamples)
 	if err != nil {
-		fmt.Printf("Error: %s\n", err)
-		os.Exit(1)
+		return err
 	}
+	return nil
 }
 
 func findTrack(moov *mp4.MoovBox, hdlrType string, trackID uint32) (*mp4.TrakBox, error) {
@@ -84,21 +92,21 @@ func findTrack(moov *mp4.MoovBox, hdlrType string, trackID uint32) (*mp4.TrakBox
 		}
 		return inTrak, nil
 	}
-	return nil, fmt.Errorf("No matching track found")
+	return nil, fmt.Errorf("no matching track found")
 }
 
-func parseProgressiveMp4(f *mp4.File, trackID uint32, maxNrSamples int) error {
+func parseProgressiveMp4(f *mp4.File, w io.Writer, trackID uint32, maxNrSamples int) error {
 	wvttTrak, err := findTrack(f.Moov, "text", trackID)
 	if err != nil {
 		return err
 	}
 
 	stbl := wvttTrak.Mdia.Minf.Stbl
 	if stbl.Stsd.Wvtt == nil {
-		return fmt.Errorf("No wvtt track found")
+		return fmt.Errorf("no wvtt track found")
 	}
 
-	fmt.Printf("Track %d, timescale = %d\n", wvttTrak.Tkhd.TrackID, wvttTrak.Mdia.Mdhd.Timescale)
+	fmt.Fprintf(w, "Track %d, timescale = %d\n", wvttTrak.Tkhd.TrackID, wvttTrak.Mdia.Mdhd.Timescale)
 	err = stbl.Stsd.Wvtt.VttC.Info(os.Stdout, "", "  ", "  ")
 	if err != nil {
 		return err
@@ -129,7 +137,7 @@ func parseProgressiveMp4(f *mp4.File, trackID uint32, maxNrSamples int) error {
 		// Next find sample bytes as slice in mdat
 		offsetInMdatData := uint64(offset) - mdatPayloadStart
 		sample := mdat.Data[offsetInMdatData : offsetInMdatData+uint64(size)]
-		err = printWvttSample(sample, sampleNr, decTime+uint64(cto), dur)
+		err = printWvttSample(w, sample, sampleNr, decTime+uint64(cto), dur)
 		if err != nil {
 			return err
 		}
@@ -140,7 +148,7 @@ func parseProgressiveMp4(f *mp4.File, trackID uint32, maxNrSamples int) error {
 	return nil
 }
 
-func parseFragmentedMp4(f *mp4.File, trackID uint32, maxNrSamples int) error {
+func parseFragmentedMp4(f *mp4.File, w io.Writer, trackID uint32, maxNrSamples int) error {
 	var wvttTrex *mp4.TrexBox
 	if f.Init != nil { // Print vttC header and timescale if moov-box is present
 		wvttTrak, err := findTrack(f.Init.Moov, "text", trackID)
@@ -150,11 +158,11 @@ func parseFragmentedMp4(f *mp4.File, trackID uint32, maxNrSamples int) error {
 
 		stbl := wvttTrak.Mdia.Minf.Stbl
 		if stbl.Stsd.Wvtt == nil {
-			return fmt.Errorf("No wvtt track found")
+			return fmt.Errorf("no wvtt track found")
 		}
 
-		fmt.Printf("Track %d, timescale = %d\n", wvttTrak.Tkhd.TrackID, wvttTrak.Mdia.Mdhd.Timescale)
-		err = stbl.Stsd.Wvtt.VttC.Info(os.Stdout, "", "  ", "  ")
+		fmt.Fprintf(w, "Track %d, timescale = %d\n", wvttTrak.Tkhd.TrackID, wvttTrak.Mdia.Mdhd.Timescale)
+		err = stbl.Stsd.Wvtt.VttC.Info(w, "  ", "", "  ")
 		if err != nil {
 			return err
 		}
@@ -167,16 +175,29 @@ func parseFragmentedMp4(f *mp4.File, trackID uint32, maxNrSamples int) error {
 	iSamples := make([]mp4.FullSample, 0)
 	for _, iSeg := range f.Segments {
 		for _, iFrag := range iSeg.Fragments {
+			var tfraTime uint64
+			if f.Mfra != nil {
+				moofOffset := iFrag.Moof.StartPos
+				entry := f.Mfra.FindEntry(moofOffset, iFrag.Moof.Traf.Tfhd.TrackID)
+				if entry != nil {
+					tfraTime = entry.Time
+				}
+			}
 			fSamples, err := iFrag.GetFullSamples(wvttTrex)
 			if err != nil {
 				return err
 			}
+			if tfraTime != 0 && fSamples[0].DecodeTime == 0 {
+				for i := range fSamples {
+					fSamples[i].DecodeTime += tfraTime
+				}
+			}
 			iSamples = append(iSamples, fSamples...)
 		}
 	}
 	var err error
 	for i, sample := range iSamples {
-		err = printWvttSample(sample.Data, i+1, sample.PresentationTime(), sample.Dur)
+		err = printWvttSample(w, sample.Data, i+1, sample.PresentationTime(), sample.Dur)
 
 		if err != nil {
 			return err
@@ -188,12 +209,12 @@ func parseFragmentedMp4(f *mp4.File, trackID uint32, maxNrSamples int) error {
 	return nil
 }
 
-func printWvttSample(sample []byte, nr int, pts uint64, dur uint32) error {
-	fmt.Printf("Sample %d, pts=%d, dur=%d\n", nr, pts, dur)
+func printWvttSample(w io.Writer, sample []byte, nr int, pts uint64, dur uint32) error {
+	fmt.Fprintf(w, "Sample %d, pts=%d, dur=%d\n", nr, pts, dur)
 	buf := bytes.NewBuffer(sample)
 	box, err := mp4.DecodeBox(0, buf)
 	if err != nil {
 		return err
 	}
-	return box.Info(os.Stdout, "", "  ", "  ")
+	return box.Info(w, "  ", "", "  ")
 }

cmd/mp4ff-wvttlister/main_test.go

@@ -0,0 +1,81 @@
+package main
+
+import (
+	"bytes"
+	"os"
+	"strings"
+	"testing"
+)
+
+var wanted = `Track 1, timescale = 1000
+[vttC] size=14
+ - config: "WEBVTT"
+Sample 1, pts=0, dur=6640
+[vttc] size=52
+  [sttg] size=18
+   - settings: align:left
+  [payl] size=26
+   - cueText: "<c.magenta>...</c>"
+Sample 2, pts=6640, dur=320
+[vtte] size=8
+Sample 3, pts=6960, dur=3040
+[vttc] size=129
+  [sttg] size=20
+   - settings: align:center
+  [payl] size=89
+   - cueText: "<c.magenta>-Tout, tout, tout pourri,</c>\n<c.magenta>tout, tout, tout plaplat,</c>"
+  [vsid] size=12
+   - sourceID: 4068696550
+Sample 4, pts=10000, dur=880
+[vttc] size=129
+  [sttg] size=20
+   - settings: align:center
+  [payl] size=89
+   - cueText: "<c.magenta>-Tout, tout, tout pourri,</c>\n<c.magenta>tout, tout, tout plaplat,</c>"
+  [vsid] size=12
+   - sourceID: 4068696550
+Sample 5, pts=10880, dur=320
+[vtte] size=8
+Sample 6, pts=11200, dur=3160
+[vttc] size=127
+  [sttg] size=20
+   - settings: align:center
+  [payl] size=99
+   - cueText: "<c.magenta>Chien Pourri et Chaplapla,</c>\n<c.magenta>c'est moi, le chien, toi, le chat.</c>"
+Sample 7, pts=14360, dur=320
+[vtte] size=8
+Sample 8, pts=14680, dur=5320
+[vttc] size=131
+  [sttg] size=20
+   - settings: align:center
+  [payl] size=91
+   - cueText: "<c.magenta>Un ami, une poubelle,</c>\n<c.magenta>et pour nous, la vie est belle.</c>"
+  [vsid] size=12
+   - sourceID: 1833399447
+`
+
+func TestWvttLister(t *testing.T) {
+	testFile := "testdata/sample_short.ismt"
+
+	ifh, err := os.Open(testFile)
+	if err != nil {
+		t.Error(err)
+	}
+	defer ifh.Close()
+	var w bytes.Buffer
+	err = run(ifh, &w, 0, -1)
+	if err != nil {
+		t.Error(err)
+	}
+	got := w.String()
+	gotLines := strings.Split(got, "\n")
+	wantedLines := strings.Split(wanted, "\n")
+	if len(gotLines) != len(wantedLines) {
+		t.Errorf("got %d lines, wanted %d", len(gotLines), len(wantedLines))
+	}
+	for i := range gotLines {
+		if gotLines[i] != wantedLines[i] {
+			t.Errorf("line %d: got: %q\n wanted %q", i, gotLines[i], wantedLines[i])
+		}
+	}
+}

mp4/file.go

@@ -31,7 +31,8 @@ type File struct {
 	Init         *InitSegment    // Init data (ftyp + moov for fragmented file)
 	Sidx         *SidxBox        // The first sidx box for a DASH OnDemand file
 	Sidxs        []*SidxBox      // All sidx boxes for a DASH OnDemand file
-	tfra         *TfraBox        // Single tfra box read at end for segmentation of ISM files
+	tfra         *TfraBox        // Single tfra box read first if DecISMFlag set
+	Mfra         *MfraBox        // MfraBox for ISM files
 	Segments     []*MediaSegment // Media segments
 	Children     []Box           // All top-level boxes in order
 	FragEncMode  EncFragFileMode // Determine how fragmented files are encoded
@@ -261,14 +262,14 @@ func (f *File) AddChild(child Box, boxStartPos uint64) {
 	case *StypBox:
 		// Starts a new segment
 		f.isFragmented = true
-		f.AddMediaSegment(NewMediaSegmentWithStyp(box))
+		f.AddMediaSegment(&MediaSegment{Styp: box, StartPos: boxStartPos})
 	case *EmsgBox:
 		// emsg box is only added at the start of a fragment (inside a segment).
 		// The case that a segment starts without an emsg is also handled.
 		f.startSegmentIfNeeded(box, boxStartPos)
 		lastSeg := f.LastSegment()
 		if len(lastSeg.Fragments) == 0 {
-			lastSeg.AddFragment(NewFragment())
+			lastSeg.AddFragment(&Fragment{StartPos: boxStartPos})
 		}
 		frag := lastSeg.LastFragment()
 		frag.AddChild(box)
@@ -280,7 +281,7 @@ func (f *File) AddChild(child Box, boxStartPos uint64) {
 		currSeg := f.LastSegment()
 		lastFrag := currSeg.LastFragment()
 		if lastFrag == nil || lastFrag.Moof != nil {
-			currSeg.AddFragment(NewFragment())
+			currSeg.AddFragment(&Fragment{StartPos: boxStartPos})
 		}
 		frag := currSeg.LastFragment()
 		frag.AddChild(moof)
@@ -291,11 +292,13 @@ func (f *File) AddChild(child Box, boxStartPos uint64) {
 			currentFragment := f.LastSegment().LastFragment()
 			currentFragment.AddChild(box)
 		}
+	case *MfraBox:
+		f.Mfra = box
 	}
 	f.Children = append(f.Children, child)
 }
 
-// startSegmentIfNeeded starts a new segment if there is none or if position match with sidx.
+// startSegmentIfNeeded starts a new segment if there is none or if position match with sidx of tfra.
 func (f *File) startSegmentIfNeeded(b Box, boxStartPos uint64) {
 	segStart := false
 	idx := len(f.Segments)
@@ -320,7 +323,13 @@ func (f *File) startSegmentIfNeeded(b Box, boxStartPos uint64) {
 	}
 	if segStart {
 		f.isFragmented = true
-		f.AddMediaSegment(NewMediaSegmentWithoutStyp())
+		ms := MediaSegment{
+			Styp:        nil,
+			Fragments:   nil,
+			EncOptimize: OptimizeNone,
+			StartPos:    boxStartPos,
+		}
+		f.AddMediaSegment(&ms)
 		return
 	}
 }
@@ -444,6 +453,12 @@ func (f *File) Encode(w io.Writer) error {
 					return err
 				}
 			}
+			if f.Mfra != nil {
+				err := f.Mfra.Encode(w)
+				if err != nil {
+					return err
+				}
+			}
 		case EncModeBoxTree:
 			for _, b := range f.Children {
 				err := b.Encode(w)

mp4/fragment.go

@@ -17,6 +17,7 @@ type Fragment struct {
 	Children    []Box       // All top-level boxes in order
 	nextTrunNr  uint32      // To handle multi-trun cases
 	EncOptimize EncOptimize // Bit field with optimizations being done at encoding
+	StartPos    uint64      // Start position in file added by parser
 }
 
 // NewFragment creates an empty MP4 Fragment.
@@ -127,12 +128,16 @@ func (f *Fragment) GetFullSamples(trex *TrexBox) ([]FullSample, error) {
 		traf = moof.Traf // The first one
 	}
 	tfhd := traf.Tfhd
-	baseTime := traf.Tfdt.BaseMediaDecodeTime()
+	var baseTime uint64
+	if traf.Tfdt != nil {
+		baseTime = traf.Tfdt.BaseMediaDecodeTime()
+	}
 	moofStartPos := moof.StartPos
 	var samples []FullSample
 	for _, trun := range traf.Truns {
 		totalDur := trun.AddSampleDefaultValues(tfhd, trex)
-		var baseOffset uint64
+		// The default is moofStartPos according to Section 8.8.7.1
+		baseOffset := moofStartPos
 		if tfhd.HasBaseDataOffset() {
 			baseOffset = tfhd.BaseDataOffset
 		} else if tfhd.DefaultBaseIfMoof() {

mp4/mediasegment.go

@@ -13,6 +13,7 @@ type MediaSegment struct {
 	Sidxs       []*SidxBox // All sidx boxes in a segment
 	Fragments   []*Fragment
 	EncOptimize EncOptimize
+	StartPos    uint64 // Start position in file
 }
 
 // NewMediaSegment - create empty MediaSegment with CMAF styp box

mp4/mfra.go

@@ -94,3 +94,13 @@ func (m *MfraBox) GetChildren() []Box {
 func (m *MfraBox) Info(w io.Writer, specificBoxLevels, indent, indentStep string) error {
 	return ContainerInfo(m, w, specificBoxLevels, indent, indentStep)
 }
+
+// FindEntry - find tfra entry for given moof start offset and trackID. Return nil if not found.
+func (m *MfraBox) FindEntry(moofStart uint64, trackID uint32) *TfraEntry {
+	for _, tfra := range m.Tfras {
+		if tfra.TrackID == trackID {
+			return tfra.FindEntry(moofStart)
+		}
+	}
+	return nil
+}