80 lines
1.3 KiB
Go
80 lines
1.3 KiB
Go
package h264
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import (
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"fmt"
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)
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// DecodeAnnexB decodes NALUs from the Annex-B code stream format.
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func DecodeAnnexB(byts []byte) ([][]byte, error) {
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bl := len(byts)
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// check initial delimiter
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n := func() int {
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if bl < 3 || byts[0] != 0x00 || byts[1] != 0x00 {
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return -1
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}
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if byts[2] == 0x01 {
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return 3
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}
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if bl < 4 || byts[2] != 0x00 || byts[3] != 0x01 {
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return -1
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}
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return 4
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}()
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if n < 0 {
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return nil, fmt.Errorf("input doesn't start with a delimiter")
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}
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var ret [][]byte
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zeros := 0
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start := n
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delimStart := 0
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for i := n; i < bl; i++ {
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switch byts[i] {
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case 0:
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if zeros == 0 {
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delimStart = i
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}
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zeros++
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case 1:
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if zeros == 2 || zeros == 3 {
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nalu := byts[start:delimStart]
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if len(nalu) == 0 {
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return nil, fmt.Errorf("empty NALU")
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}
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ret = append(ret, nalu)
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start = i + 1
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}
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zeros = 0
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default:
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zeros = 0
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}
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}
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nalu := byts[start:bl]
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if len(nalu) == 0 {
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return nil, fmt.Errorf("empty NALU")
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}
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ret = append(ret, nalu)
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return ret, nil
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}
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// EncodeAnnexB encodes NALUs into the Annex-B code stream format.
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func EncodeAnnexB(nalus [][]byte) ([]byte, error) {
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var ret []byte
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for _, nalu := range nalus {
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ret = append(ret, []byte{0x00, 0x00, 0x00, 0x01}...)
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ret = append(ret, nalu...)
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}
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return ret, nil
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}
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