59 lines
1.1 KiB
Go
59 lines
1.1 KiB
Go
package h264
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import (
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"time"
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)
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// DTSEstimator is a DTS estimator.
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type DTSEstimator struct {
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initializing int
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prevDTS time.Duration
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prevPTS time.Duration
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prevPrevPTS time.Duration
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}
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// NewDTSEstimator allocates a DTSEstimator.
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func NewDTSEstimator() *DTSEstimator {
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return &DTSEstimator{
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initializing: 2,
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}
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}
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// Feed provides PTS to the estimator, and returns the estimated DTS.
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func (d *DTSEstimator) Feed(pts time.Duration) time.Duration {
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if d.initializing > 0 {
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d.initializing--
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dts := d.prevDTS + time.Millisecond
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d.prevPrevPTS = d.prevPTS
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d.prevPTS = pts
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d.prevDTS = dts
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return dts
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}
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dts := func() time.Duration {
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// P or I frame
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if pts > d.prevPTS {
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// previous frame was B
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// use the DTS of the previous frame
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if d.prevPTS < d.prevPrevPTS {
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return d.prevPTS
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}
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// previous frame was P or I
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// use two frames ago plus a small quantity
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// to avoid non-monotonous DTS with B-frames
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return d.prevPrevPTS + time.Millisecond
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}
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// B Frame
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// do not increase
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return d.prevDTS + time.Millisecond
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}()
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d.prevPrevPTS = d.prevPTS
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d.prevPTS = pts
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d.prevDTS = dts
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return dts
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}
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