Merge pull request #52 from edgeware/fix-number-offset

Bug fix version 0.16.2

README.md

@@ -113,6 +113,11 @@ This value is the address of the first media sample relative to the start of the
 It therefore depends on the size of `MoofBox` and is unknown until all values are in place so that
 it can be calculated. It is set to `MoofBox.Size()+8`.
 
+## Sample Number Offset
+Following the ISOBMFF standard, sample numbers and other numbers start at 1 (one-based).
+This applies to arguments of functions. The actual storage in slices are zero-based, so
+sample nr 1 has index 0 in the corresponding slice.
+
 ## Command Line Tools
 
 Some simple command line tools are available in `cmd`.
@@ -136,6 +141,11 @@ These are
 ## Stability
 The APIs should be fairly stable, but minor non-backwards-compatible tweaks may happen until version 1.
 
+## Specifications
+The main specification for the MP4 file format is the ISO Base Media File Format (ISOBMFF) standard
+ISO/IEC 14496-12 6'th ed 2020. Some boxes are specified in other standards, as should be commented
+in the code.
+
 ## LICENSE
 
 MIT, see [LICENSE.md](LICENSE.md).

Versions.md

@@ -2,6 +2,7 @@
 
 | Version | Highlight |
 | ------  | --------- |
+| 0.16.2 | fix: Minor fixes to sampleNumber and tfhd Info |
 | 0.16.1 | fix: isNonSync flag declaration and use sdtp values in segmenter example |
 | 0.16.0 | New mp4ff-info tool. Many new boxes incl. encryption boxes and sdtp. ADTS support. Test improvements with golden files |
 | 0.15.0 | Support for multiple SPS and more explicit NALU types for AVC |

examples/segmenter/segment.go

@@ -96,14 +96,14 @@ func (s *Segmenter) GetSamplesUntilTime(mp4f *mp4.File, tr *Track, startSampleNr
 		}
 		var sampleFlags mp4.SampleFlags
 		if stbl.Stss != nil {
-			isSync := stbl.Stss.IsSyncSample(uint32(sampleNr - 1))
+			isSync := stbl.Stss.IsSyncSample(uint32(sampleNr))
 			sampleFlags.SampleIsNonSync = !isSync
 			if isSync {
 				sampleFlags.SampleDependsOn = 2 //2 = does not depend on others (I-picture). May be overridden by sdtp entry
 			}
 		}
 		if stbl.Sdtp != nil {
-			entry := stbl.Sdtp.Entries[uint32(sampleNr)-1]
+			entry := stbl.Sdtp.Entries[uint32(sampleNr)-1] // table starts at 0, but sampleNr is one-based
 			sampleFlags.IsLeading = entry.IsLeading()
 			sampleFlags.SampleDependsOn = entry.SampleDependsOn()
 			sampleFlags.SampleHasRedundancy = entry.SampleHasRedundancy()

mp4/ctts.go

@@ -4,6 +4,7 @@ import (
 	"encoding/binary"
 	"io"
 	"io/ioutil"
+	"log"
 )
 
 // CttsBox - Composition Time to Sample Box (ctts - optional)
@@ -69,9 +70,14 @@ func (b *CttsBox) Encode(w io.Writer) error {
 	return err
 }
 
-// GetCompositionTimeOffset - composition time offset for sampleNr in track timescale
+// GetCompositionTimeOffset - composition time offset for (one-based) sampleNr in track timescale
 func (b *CttsBox) GetCompositionTimeOffset(sampleNr uint32) int32 {
-	sampleNr-- // 1-based
+	if sampleNr == 0 {
+		// This is bad index input. Should not happen
+		log.Print("ERROR: CttsBox.GetCompositionTimeOffset called with sampleNr == 0, although one-based")
+		return 0
+	}
+	sampleNr-- // one-based
 	for i := range b.SampleCount {
 		if sampleNr >= b.SampleCount[i] {
 			sampleNr -= b.SampleCount[i]

mp4/stsc.go

@@ -92,7 +92,7 @@ func (b *StscBox) Info(w io.Writer, specificBoxLevels, indent, indentStep string
 	return bd.err
 }
 
-// ChunkNrFromSampleNr - get chunk number from sampleNr (1-based)
+// ChunkNrFromSampleNr - get chunk number from sampleNr (one-based)
 func (b *StscBox) ChunkNrFromSampleNr(sampleNr int) (chunkNr, firstSampleInChunk int, err error) {
 	nrEntries := len(b.FirstChunk) // Nr entries in stsc box
 	firstSampleInChunk = 1

mp4/stss.go

@@ -48,7 +48,7 @@ func (b *StssBox) Size() uint64 {
 	return uint64(boxHeaderSize + 8 + len(b.SampleNumber)*4)
 }
 
-// IsSyncSample - check if a sample is a sync sample
+// IsSyncSample - check if sample (one-based) sampleNr is a sync sample
 func (b *StssBox) IsSyncSample(sampleNr uint32) (isSync bool) {
 	if b.lookUp == nil {
 		b.lookUp = make(map[uint32]bool)

mp4/stts.go

@@ -4,6 +4,7 @@ import (
 	"encoding/binary"
 	"io"
 	"io/ioutil"
+	"log"
 	"time"
 )
 
@@ -72,9 +73,14 @@ func (b *SttsBox) GetTimeCode(sample, timescale uint32) time.Duration {
 	return time.Second * time.Duration(units) / time.Duration(timescale)
 }
 
-// GetDecodeTime - decode time and duration for sampleNr in track timescale
+// GetDecodeTime - decode time and duration for (one-based) sampleNr in track timescale
 func (b *SttsBox) GetDecodeTime(sampleNr uint32) (decTime uint64, dur uint32) {
-	sampleNr-- // 1-based
+	if sampleNr == 0 {
+		// This is bad index input. Should not happen
+		log.Print("ERROR: SttsBox.GetDecodeTime called with sampleNr == 0, although one-based")
+		return 0, 1
+	}
+	sampleNr-- // one-based
 	decTime = 0
 	i := 0
 	for sampleNr > 0 && i < len(b.SampleCount) {
@@ -89,7 +95,7 @@ func (b *SttsBox) GetDecodeTime(sampleNr uint32) (decTime uint64, dur uint32) {
 		}
 		i++
 	}
-	return
+	return decTime, dur
 }
 
 // Encode - write box to w

mp4/testdata/golden_1_frag_m4s_dump.txt

@@ -12,7 +12,7 @@
      - trackID: 2
      - defaultBaseIsMoof: true
      - defaultSampleDuration: 3000
-     - defaultSampleFlags: 01010000
+     - defaultSampleFlags: 01010000 (isLeading=0 dependsOn=1 isDependedOn=0 hasRedundancy=0 padding=0 isNonSync=true degradationPriority=0)
     [tfdt] size=16 version=0
      - baseMediaDecodeTime: 0
     [trun] size=144 version=1
@@ -45,7 +45,7 @@
      - trackID: 2
      - defaultBaseIsMoof: true
      - defaultSampleDuration: 3000
-     - defaultSampleFlags: 01010000
+     - defaultSampleFlags: 01010000 (isLeading=0 dependsOn=1 isDependedOn=0 hasRedundancy=0 padding=0 isNonSync=true degradationPriority=0)
     [tfdt] size=16 version=0
      - baseMediaDecodeTime: 45000
     [trun] size=140 version=1
@@ -77,7 +77,7 @@
      - trackID: 2
      - defaultBaseIsMoof: true
      - defaultSampleDuration: 3000
-     - defaultSampleFlags: 01010000
+     - defaultSampleFlags: 01010000 (isLeading=0 dependsOn=1 isDependedOn=0 hasRedundancy=0 padding=0 isNonSync=true degradationPriority=0)
     [tfdt] size=16 version=0
      - baseMediaDecodeTime: 90000
     [trun] size=144 version=1
@@ -110,7 +110,7 @@
      - trackID: 2
      - defaultBaseIsMoof: true
      - defaultSampleDuration: 3000
-     - defaultSampleFlags: 01010000
+     - defaultSampleFlags: 01010000 (isLeading=0 dependsOn=1 isDependedOn=0 hasRedundancy=0 padding=0 isNonSync=true degradationPriority=0)
     [tfdt] size=16 version=0
      - baseMediaDecodeTime: 135000
     [trun] size=140 version=1

mp4/tfhd.go

@@ -194,7 +194,8 @@ func (t *TfhdBox) Info(w io.Writer, specificBoxLevels, indent, indentStep string
 		bd.write(" - defaultSampleSize: %d", t.DefaultSampleSize)
 	}
 	if t.HasDefaultSampleFlags() {
-		bd.write(" - defaultSampleFlags: %08x", t.DefaultSampleFlags)
+		bd.write(" - defaultSampleFlags: %08x (%s)", t.DefaultSampleFlags, DecodeSampleFlags(t.DefaultSampleFlags))
+
 	}
 	return bd.err
 }