mirror of https://bitbucket.org/ausocean/av.git
codec/mjpeg/extract.go: wrote Extractor type
Wrote extractor type that provides an Extract function to extract JPEG frames from an RTP/MJPEG stream and writes them to a destination.
This commit is contained in:
Saxon
parent
c2ce700cbd
commit
ba25cdfd12
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@ -0,0 +1,288 @@
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/*
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DESCRIPTION
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extract.go provides an Extractor to get JPEG from RTP.
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AUTHOR
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Saxon Nelson-Milton <saxon@ausocean.org>
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LICENSE
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Copyright (C) 2017 the Australian Ocean Lab (AusOcean)
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It is free software: you can redistribute it and/or modify them
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under the terms of the GNU General Public License as published by the
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Free Software Foundation, either version 3 of the License, or (at your
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option) any later version.
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It is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with revid in gpl.txt. If not, see http://www.gnu.org/licenses.
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*/
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package mjpeg
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import (
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"bytes"
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"fmt"
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"io"
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"time"
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"errors"
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"bitbucket.org/ausocean/av/protocol/rtp"
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)
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// Buffer sizes.
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const (
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maxRTPSize = 1500 // Max ethernet transmission unit in bytes.
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)
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var (
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errNoQTable = errors.New("no quantization table")
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errReservedQ = errors.New("q value is reserved")
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)
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var defaultQuantisers = []byte{
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// Luma table.
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16, 11, 12, 14, 12, 10, 16, 14,
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13, 14, 18, 17, 16, 19, 24, 40,
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26, 24, 22, 22, 24, 49, 35, 37,
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29, 40, 58, 51, 61, 60, 57, 51,
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56, 55, 64, 72, 92, 78, 64, 68,
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87, 69, 55, 56, 80, 109, 81, 87,
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95, 98, 103, 104, 103, 62, 77, 113,
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121, 112, 100, 120, 92, 101, 103, 99,
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/* chroma table */
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17, 18, 18, 24, 21, 24, 47, 26,
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26, 47, 99, 66, 56, 66, 99, 99,
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99, 99, 99, 99, 99, 99, 99, 99,
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99, 99, 99, 99, 99, 99, 99, 99,
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99, 99, 99, 99, 99, 99, 99, 99,
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99, 99, 99, 99, 99, 99, 99, 99,
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99, 99, 99, 99, 99, 99, 99, 99,
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99, 99, 99, 99, 99, 99, 99, 99,
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}
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// Extractor is an Extractor for extracting JPEG from an RTP stream.
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type Extractor struct {
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buf *bytes.Buffer // Holds the current JPEG image.
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dst io.Writer // The destination we'll be writing extracted NALUs to.
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}
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// NewExtractor returns a new Extractor.
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func NewExtractor() *Extractor { return &Extractor{} }
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// Extract will continously read RTP packets from src containing JPEG (in RTP
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// payload format) and extract the JPEG images, sending them to dst. This
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// function expects that each read from src will provide a single RTP packet.
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func (e *Extractor) Extract(dst io.Writer, src io.Reader, delay time.Duration) error {
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buf := make([]byte, maxRTPSize)
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var (
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qTables [128][128]byte
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qTablesLen [128]byte
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)
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for {
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n, err := src.Read(buf)
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switch err {
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case nil: // Do nothing.
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case io.EOF:
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return nil
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default:
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return fmt.Errorf("source read error: %v\n", err)
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}
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// Get payload from RTP packet.
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p, err := rtp.Payload(buf[:n])
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if err != nil {
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return fmt.Errorf("could not get RTP payload, failed with err: %v\n", err)
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}
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b := newByteStream(p)
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_ = b.get8() // Ignore type-specific flag
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var (
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off = b.get24() // Fragment offset.
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t = b.get8() // Type.
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q = b.get8() // Quantization value.
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width = b.get8() // Picture width.
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height = b.get8() // Picture height.
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dri int // Restart interval.
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)
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if t&0x40 != 0 {
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dri = b.get16()
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_ = b.get16() // Ignore restart count.
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t &= ^0x40
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}
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if t > 1 {
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panic("unimplemented RTP/JPEG type")
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}
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// Parse quantization table if our offset is 0.
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if off == 0 {
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var qTable []byte
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var qLen int
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if q > 127 {
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_ = b.get8() // Ignore first byte (reserved for future use).
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prec := b.get8() // The size of coefficients.
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qLen = b.get16() // The length of the quantization table.
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if prec != 0 {
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panic("unsupported precision")
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}
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if qLen > 0 {
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qTable = b.getBuf(qLen)
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if q < 255 {
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if qTablesLen[q-128] == 0 && qLen <= 128 {
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copy(qTables[q-128][:],qTable)
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qTablesLen[q-128] = byte(qLen)
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}
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}
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} else {
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if q == 255 {
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return errNoQTable
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}
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if qTablesLen[q-128] == 0 {
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return fmt.Errorf("no quantization tables known for q %d yet",q)
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}
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qTable = qTables[q-128][:]
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qLen = int(qTablesLen[q-128])
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}
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} else { // q <= 127
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if q == 0 || q > 99 {
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return errReservedQ
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}
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qTable = defaultQTable(q)
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qLen = len(qTable)
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}
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e.buf.Reset()
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err = writeHeader(e.buf, t, width, height, qLen / 64, dri, qTable)
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if err != nil {
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return fmt.Errorf("could not write JPEG header: %w",err)
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}
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}
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if e.buf.Len() == 0 {
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// Must have missed start of frame? So ignore and wait for start.
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continue
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}
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// TODO: check that timestamp is consistent
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// This will need expansion to RTP package to create Timestamp parsing func.
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// TODO: could also check offset with how many bytes we currently have
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// to determine if there are missing frames.
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// Write frame data
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err = b.writeTo(e.buf,b.remaining())
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if err != nil {
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return fmt.Errorf("could not write remaining frame data to output buffer: %w",err)
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}
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m, err := rtp.Marker(buf[:n])
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if err != nil {
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return fmt.Errorf("could not read RTP marker: %w",err)
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}
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if m {
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_,err = e.buf.Write([]byte{0xff,codeEOI})
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if err != nil {
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return fmt.Errorf("could not write EOI marker: %w",err)
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}
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_,err = e.buf.WriteTo(dst)
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if err != nil {
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return fmt.Errorf("could not write JPEG to dst: %w",err)
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}
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}
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}
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}
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type byteStream struct {
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bytes []byte
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i int
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}
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func newByteStream(b []byte) *byteStream { return &byteStream{bytes: b} }
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func (b *byteStream) get24() int {
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v := int(b.bytes[b.i])<<16 | int(b.bytes[b.i+1])<<8 | int(b.bytes[b.i+2])
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b.i += 3
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return v
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}
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func (b *byteStream) get8() int {
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v := int(b.bytes[b.i])
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b.i++
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return v
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}
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func (b *byteStream) get16() int {
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v := int(b.bytes[b.i])<<8 | int(b.bytes[b.i+1])
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b.i += 2
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return v
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}
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func (b *byteStream) getBuf(n int) []byte {
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v := b.bytes[b.i:b.i+n]
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b.i += n
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return v
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}
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func (b *byteStream) remaining() int {
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return len(b.bytes) - b.i
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}
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func (b *byteStream) writeTo(w io.Writer, n int) error {
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_n,err := w.Write(b.bytes[b.i:n])
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b.i += _n
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if err != nil {
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return err
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}
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return nil
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}
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func defaultQTable(q int) []byte {
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f := clip(q,q,99)
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const tabLen = 128
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tab := make([]byte,tabLen)
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if q < 50 {
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q = 5000 / f
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} else {
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q = 200 - f*2
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}
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for i := 0; i < tabLen; i++ {
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v := (int(defaultQuantisers[i])*q + 50) / 100
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v = clip(v,1,255)
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tab[i] = byte(v)
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}
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return tab
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}
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func clip(v, min, max int) int {
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if v < min {
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return min
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}
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if v > max {
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return max
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}
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return v
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}
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@ -39,6 +39,7 @@ const (
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codeSOS = 0xda // Start of scan.
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codeAPP0 = 0xe0 // TODO: find out what this is.
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codeSOF0 = 0xc0 // Baseline
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codeEOI = 0xd9 // End of image.
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)
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var (
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@ -96,42 +97,37 @@ var (
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}
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)
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// writeMarker writes an JPEG marker with code to w.
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func writeMarker(w io.Writer, code byte) error {
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_, err := w.Write([]byte{0xff, code})
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if err != nil {
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return err
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}
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return nil
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type multiError []error
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func (me multiError) Error() string {
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return fmt.Sprintf("%v", []error(me))
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}
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// writeHuffman write a JPEG huffman table to w.
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func writeHuffman(w io.Writer, class, id int, bits, values []byte) error {
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_, err := w.Write([]byte{byte(class<<4 | id)})
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if err != nil {
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return fmt.Errorf("could not write class and id: %w", err)
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func (me multiError) add(e error) {
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me = append(me, e)
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}
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var n int
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for i := 1; i <= 16; i++ {
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n += int(bits[i])
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type putter struct {
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idx int
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}
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_, err = w.Write(bits[1:17])
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if err != nil {
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return fmt.Errorf("could not write first lot of huffman bytes: %w", err)
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func (p *putter) put16(b []byte, v uint16) {
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binary.BigEndian.PutUint16(b[p.idx:], v)
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p.idx += 2
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}
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_, err = w.Write(values[0:n])
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if err != nil {
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return fmt.Errorf("could not write second lot of huffman bytes: %w", err)
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func (p *putter) put8(b []byte, v uint8) {
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b[p.idx] = byte(v)
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p.idx++
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}
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return nil
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func (p *putter) putBuf(dst, src []byte, l int) {
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copy(dst[p.idx:], src)
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p.idx++
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}
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// writeHeader writes a JPEG header to the writer w.
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func writeHeader(w io.Writer, size, _type, width, height, nbqTab, dri int, qtable []byte) error {
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func writeHeader(w io.Writer, _type, width, height, nbqTab, dri int, qtable []byte) error {
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width <<= 3
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height <<= 3
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@ -282,31 +278,36 @@ func writeHeader(w io.Writer, size, _type, width, height, nbqTab, dri int, qtabl
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return nil
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}
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type multiError []error
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func (me multiError) Error() string {
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return fmt.Sprintf("%v", []error(me))
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// writeMarker writes an JPEG marker with code to w.
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func writeMarker(w io.Writer, code byte) error {
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_, err := w.Write([]byte{0xff, code})
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if err != nil {
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return err
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}
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return nil
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}
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func (me multiError) add(e error) {
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me = append(me, e)
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// writeHuffman write a JPEG huffman table to w.
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func writeHuffman(w io.Writer, class, id int, bits, values []byte) error {
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_, err := w.Write([]byte{byte(class<<4 | id)})
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if err != nil {
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return fmt.Errorf("could not write class and id: %w", err)
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}
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type putter struct {
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idx int
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var n int
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for i := 1; i <= 16; i++ {
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n += int(bits[i])
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}
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func (p *putter) put16(b []byte, v uint16) {
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binary.BigEndian.PutUint16(b[p.idx:], v)
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p.idx += 2
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_, err = w.Write(bits[1:17])
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if err != nil {
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return fmt.Errorf("could not write first lot of huffman bytes: %w", err)
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}
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func (p *putter) put8(b []byte, v uint8) {
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b[p.idx] = byte(v)
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p.idx++
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_, err = w.Write(values[0:n])
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if err != nil {
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return fmt.Errorf("could not write second lot of huffman bytes: %w", err)
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}
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func (p *putter) putBuf(dst, src []byte, l int) {
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copy(dst[p.idx:], src)
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p.idx++
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return nil
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}
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