/* NAME parse.go DESCRIPTION See Readme.md AUTHOR Dan Kortschak <dan@ausocean.org> LICENSE parse.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 parse provides parsers for video encodings. package parse import ( "bufio" "bytes" "fmt" "io" "time" ) var noDelay = make(chan time.Time) func init() { close(noDelay) } var h264Prefix = [...]byte{0x00, 0x00, 0x01, 0x09, 0xf0} // H264 parses 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 at type 1 (Coded slice of a non-IDR picture), 5 // (Coded slice of a IDR picture) and 8 (Picture parameter set). func H264(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 } r := bufio.NewReader(src) buf := make([]byte, len(h264Prefix), 4<<10) copy(buf, h264Prefix[:]) var zeroes int for { b, err := r.ReadByte() if err != nil { if err != io.EOF { return err } if len(buf) == len(h264Prefix) { return nil } <-tick _, err = dst.Write(buf) return err } if b == 0 { zeroes++ } if (zeroes == 2 || zeroes == 3) && b == 1 && len(buf)-len(h264Prefix) > zeroes { b, err = r.ReadByte() if err != nil { if err == io.EOF { err = io.ErrUnexpectedEOF } return err } const ( nonIdrPic = 1 idrPic = 5 paramSet = 8 ) switch nalTyp := b & 0x1f; nalTyp { case nonIdrPic, idrPic, paramSet: <-tick _, err = dst.Write(buf[:len(buf)-zeroes]) if err != nil { return err } buf = make([]byte, zeroes+len(h264Prefix), 4<<10) copy(buf, h264Prefix[:]) zeroes = 0 } buf = append(buf, 1, b) continue } if b != 0 { zeroes = 0 } buf = append(buf, b) } } // MJPEG parses MJPEG frames read from src into separate writes to dst with // successive writes being performed not earlier than the specified delay. func MJPEG(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 } r := bufio.NewReader(src) for { buf := make([]byte, 2, 4<<10) n, err := r.Read(buf) if n < 2 { return nil } if err != nil { return err } if !bytes.Equal(buf, []byte{0xff, 0xd8}) { return fmt.Errorf("parser: not MJPEG frame start: %#v", buf) } var last byte for { b, err := r.ReadByte() if err != nil { return err } buf = append(buf, b) if last == 0xff && b == 0xd9 { break } last = b } <-tick _, err = dst.Write(buf) if err != nil { return err } } }