av/packets/Nal.go

/*
NAME
  PES.go -
DESCRIPTION
  See Readme.md

AUTHOR
  Saxon Nelson-Milton <saxon.milton@gmail.com>

LICENSE
  PES.go is Copyright (C) 2017 the Australian Ocean Lab (AusOcean)

  It is free software: you can redistribute it and/or modify them
  under the terms of the GNU General Public License as published by the
  Free Software Foundation, either version 3 of the License, or (at your
  option) any later version.

  It is distributed in the hope that it will be useful, but WITHOUT
  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
 for more details.

  You should have received a copy of the GNU General Public License
  along with revid in gpl.txt.  If not, see [GNU licenses](http://www.gnu.org/licenses).
*/

package packets

type NALUnit interface {
  ToByteSlice() []byte
  GetType() byte
}

type NALSpsPps struct {
  Data []byte
}

type NALFragment struct {
  ThreeNUBs byte
  FragmentType byte
  Start bool
  End bool
  Reserved bool
  FiveNUBs byte
  Data []byte
}


func GetNalType(unit []byte) byte {
  return unit[0] & 0x1F
}

/*
First byte:  [ 3 NAL UNIT BITS | 5 FRAGMENT TYPE BITS]
Second byte: [ START BIT | END BIT | RESERVED BIT | 5 NAL UNIT BITS]
Other bytes: [... VIDEO FRAGMENT DATA...]
*/
func ParseNALFragment(unit []byte) (u *NALFragment) {
  u = new(NALFragment)
  u.ThreeNUBs = (unit[0] & 0xE0) >> 5
  u.FragmentType = unit[0] & 0x1F
  u.Start = (unit[1] & 0x80) != 0
  u.End = (unit[1] & 0x40) != 0
  u.Reserved = (unit[1] & 0x20) != 0
  u.FiveNUBs = unit[1] & 0x1F
  u.Data = make([]byte,len(unit[2:]))
  copy(u.Data[:],unit[2:])
  return
}

func ParseNALSpsPps(unit []byte)(u *NALSpsPps){
  u = new(NALSpsPps)
  u.Data = make([]byte,len(unit))
  copy(u.Data[:],unit[:])
  return
}

func (u *NALFragment) ToByteSlice() (output []byte) {
  output = make([]byte, 2+len(u.Data))
  output[0] = ( u.ThreeNUBs << 5 ) | u.FragmentType
  output[1] = boolToByte( u.Start ) << 7 |
              boolToByte( u.End ) << 6  |
              boolToByte( u.Reserved ) << 5  |
              u.FiveNUBs
  copy(output[2:],u.Data)
  return
}

func (u *NALFragment) GetType() byte {
  return GetNalType(u.ToByteSlice())
}

func (u *NALSpsPps) GetType() byte {
  return GetNalType(u.ToByteSlice())
}

func (u *NALSpsPps) ToByteSlice() (output []byte){
  output = make([]byte,len(u.Data))
  output = u.Data
  return
}