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h264: fix DTS extractor with B-frames and remove PTS-DTS offset

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aler9
2022-06-03 10:27:05 +02:00
parent 787c516d79
commit bcd6f1b549
3 changed files with 52 additions and 25 deletions
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37
pkg/h264/dtsextractor.go
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@@ -96,12 +96,13 @@ func getPOCDiff(poc1 uint32, poc2 uint32, sps *SPS) int32 {
// DTSExtractor is a utility that allows to extract NALU DTS from PTS.
type DTSExtractor struct {
sps []byte
spsp *SPS
prevPTS time.Duration
prevDTS time.Duration
prevPOCDiff int32
expectedPOC uint32
sps []byte
spsp *SPS
prevPTS time.Duration
prevDTS time.Duration
prevPOCDiff int32
expectedPOC uint32
ptsDTSOffset time.Duration
}
// NewDTSExtractor allocates a DTSExtractor.
@@ -128,6 +129,14 @@ func (d *DTSExtractor) extractInner(
}
d.sps = append([]byte(nil), nalu...)
d.spsp = &spsp
// in case of B-frames, we have to subtract from DTS the maximum number of reordered frames
if d.spsp.VUI != nil && d.spsp.VUI.TimingInfo != nil {
d.ptsDTSOffset = time.Duration(math.Round(float64(time.Duration(d.spsp.VUI.MaxNumReorderFrames)*time.Second*
time.Duration(d.spsp.VUI.TimingInfo.NumUnitsInTick)*2) / float64(d.spsp.VUI.TimingInfo.TimeScale)))
} else {
d.ptsDTSOffset = 0
}
}
// set IDR present flag
@@ -142,7 +151,7 @@ func (d *DTSExtractor) extractInner(
if idrPresent || d.spsp.PicOrderCntType == 2 {
d.expectedPOC = 0
return pts, 0, nil
return pts - d.ptsDTSOffset, 0, nil
}
// compute expectedPOC immediately in order to store it even in case of errors
@@ -157,6 +166,11 @@ func (d *DTSExtractor) extractInner(
pocDiff := getPOCDiff(poc, d.expectedPOC, d.spsp)
if pocDiff == 0 {
return pts - d.ptsDTSOffset, 0, nil
}
// special case to eliminate errors near 0
if d.spsp.VUI != nil && d.spsp.VUI.TimingInfo != nil && pocDiff == -int32(d.spsp.VUI.MaxNumReorderFrames)*2 {
return pts, pocDiff, nil
}
@@ -165,12 +179,13 @@ func (d *DTSExtractor) extractInner(
return 0, 0, fmt.Errorf("invalid frame POC")
}
return d.prevPTS + time.Duration(math.Round(float64(pts-d.prevPTS)/float64(pocDiff/2+1))), pocDiff, nil
return d.prevPTS - d.ptsDTSOffset +
time.Duration(math.Round(float64(pts-d.prevPTS)/float64(pocDiff/2+1))), pocDiff, nil
}
// pocDiff : prevPOCDiff = (pts - dts) : (prevPTS - prevDTS)
return pts + time.Duration(math.Round(float64(d.prevDTS-d.prevPTS)*float64(pocDiff)/float64(d.prevPOCDiff))),
pocDiff, nil
// pocDiff : prevPOCDiff = (pts - dts - ptsDTSOffset) : (prevPTS - prevDTS - ptsDTSOffset)
return pts - d.ptsDTSOffset + time.Duration(math.Round(float64(d.prevDTS-d.prevPTS+d.ptsDTSOffset)*
float64(pocDiff)/float64(d.prevPOCDiff))), pocDiff, nil
}
// Extract extracts the DTS of a NALU group.