mirror of https://bitbucket.org/ausocean/av.git
134 lines
3.0 KiB
Go
134 lines
3.0 KiB
Go
/*
|
|
NAME
|
|
lex.go
|
|
|
|
DESCRIPTION
|
|
lex.go provides a lexer to lex h264 bytestream into access units.
|
|
|
|
AUTHOR
|
|
Dan Kortschak <dan@ausocean.org>
|
|
Saxon Nelson-Milton <saxon@ausocean.org>
|
|
|
|
LICENSE
|
|
lex.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 http://www.gnu.org/licenses.
|
|
*/
|
|
|
|
// Package h264 provides a h264 bytestream lexer and RTP H264 access unit
|
|
// extracter.
|
|
package h264
|
|
|
|
import (
|
|
"io"
|
|
"time"
|
|
|
|
"bitbucket.org/ausocean/av/codec/codecutil"
|
|
)
|
|
|
|
var noDelay = make(chan time.Time)
|
|
|
|
func init() {
|
|
close(noDelay)
|
|
}
|
|
|
|
var h264Prefix = [...]byte{0x00, 0x00, 0x01, 0x09, 0xf0}
|
|
|
|
// Lex lexes H.264 NAL units read from src into separate writes
|
|
// to dst with successive writes being performed not earlier than the specified
|
|
// delay. NAL units are split after type 1 (Coded slice of a non-IDR picture), 5
|
|
// (Coded slice of a IDR picture) and 8 (Picture parameter set).
|
|
func Lex(dst io.Writer, src io.Reader, delay time.Duration) error {
|
|
var tick <-chan time.Time
|
|
if delay == 0 {
|
|
tick = noDelay
|
|
} else {
|
|
ticker := time.NewTicker(delay)
|
|
defer ticker.Stop()
|
|
tick = ticker.C
|
|
}
|
|
|
|
const bufSize = 8 << 10
|
|
|
|
c := codecutil.NewByteScanner(src, make([]byte, 4<<10)) // Standard file buffer size.
|
|
|
|
buf := make([]byte, len(h264Prefix), bufSize)
|
|
copy(buf, h264Prefix[:])
|
|
writeOut := false
|
|
|
|
for {
|
|
var b byte
|
|
var err error
|
|
buf, b, err = c.ScanUntil(buf, 0x00)
|
|
if err != nil {
|
|
if err != io.EOF {
|
|
return err
|
|
}
|
|
if len(buf) != 0 {
|
|
return io.ErrUnexpectedEOF
|
|
}
|
|
return io.EOF
|
|
}
|
|
|
|
for n := 1; b == 0x0 && n < 4; n++ {
|
|
b, err = c.ReadByte()
|
|
if err != nil {
|
|
if err != io.EOF {
|
|
return err
|
|
}
|
|
return io.ErrUnexpectedEOF
|
|
}
|
|
buf = append(buf, b)
|
|
|
|
if b != 0x1 || (n != 2 && n != 3) {
|
|
continue
|
|
}
|
|
|
|
if writeOut {
|
|
<-tick
|
|
_, err := dst.Write(buf[:len(buf)-(n+1)])
|
|
if err != nil {
|
|
return err
|
|
}
|
|
buf = make([]byte, len(h264Prefix)+n, bufSize)
|
|
copy(buf, h264Prefix[:])
|
|
buf = append(buf, 1)
|
|
writeOut = false
|
|
}
|
|
|
|
b, err = c.ReadByte()
|
|
if err != nil {
|
|
if err != io.EOF {
|
|
return err
|
|
}
|
|
return io.ErrUnexpectedEOF
|
|
}
|
|
buf = append(buf, b)
|
|
|
|
// http://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-H.264-200305-S!!PDF-E&type=items
|
|
// Table 7-1 NAL unit type codes
|
|
const (
|
|
nonIdrPic = 1
|
|
idrPic = 5
|
|
suppEnhInfo = 6
|
|
paramSet = 8
|
|
)
|
|
switch nalTyp := b & 0x1f; nalTyp {
|
|
case nonIdrPic, idrPic, paramSet, suppEnhInfo:
|
|
writeOut = true
|
|
}
|
|
}
|
|
}
|
|
}
|