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rfc2435jpeg.py
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rfc2435jpeg.py
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# -*- coding: utf-8 -*-
'''
This module handles RTP payload for MJPEG codec as described in RFC2435.
JPEG header restoration code is taken from that RFC, but adapted to Python.
'''
# The following code can be used to create a quantization table from a
# Q factor:
# Tables with leading underscores are alternative, but not from the
# specification. I took them from a certain JPEG image.
_jpeg_luma_quantizer = [
16, 11, 10, 16, 24, 40, 51, 61,
12, 12, 14, 19, 26, 58, 60, 55,
14, 13, 16, 24, 40, 57, 69, 56,
14, 17, 22, 29, 51, 87, 80, 62,
18, 22, 37, 56, 68, 109, 103, 77,
24, 35, 55, 64, 81, 104, 113, 92,
49, 64, 78, 87, 103, 121, 120, 101,
72, 92, 95, 98, 112, 100, 103, 99]
_jpeg_chroma_quantizer = [
17, 18, 24, 47, 99, 99, 99, 99,
18, 21, 26, 66, 99, 99, 99, 99,
24, 26, 56, 99, 99, 99, 99, 99,
47, 66, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99]
jpeg_luma_quantizer = [
16, 11, 12, 14, 12, 10, 16, 14,
13, 14, 18, 17, 16, 19, 24, 40,
26, 24, 22, 22, 24, 49, 35, 37,
29, 40, 58, 51, 61, 60, 57, 51,
56, 55, 64, 72, 92, 78, 64, 68,
87, 69, 55, 56, 80, 109, 81, 87,
95, 98, 103, 104, 103, 62, 77, 113,
121, 112, 100, 120, 92, 101, 103, 99]
jpeg_chroma_quantizer = [
17, 18, 18, 24, 21, 24, 47, 26,
26, 47, 99, 66, 56, 66, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99]
# Call MakeTables with the Q factor and two u_char[64] return arrays
def MakeTables(q, lqt, cqt):
i = 0
factor = q
if q < 1:
factor = 1.0
if q > 99:
factor = 99.0
if q < 50:
_q = 5000.0 / factor
else:
_q = 200.0 - factor*2
for i in range(64):
lq = int((jpeg_luma_quantizer[i] * _q + 50.0) / 100.0)
cq = int((jpeg_chroma_quantizer[i] * _q + 50.0) / 100.0)
# Limit the quantizers to 1 <= q <= 255
if lq < 1:
lq = 1
elif lq > 255:
lq = 255
lqt.append(lq)
if cq < 1:
cq = 1
elif cq > 255:
cq = 255
cqt.append(cq)
# Reconstruct Header
lum_dc_codelens = [0, 1, 5, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0]
lum_dc_symbols = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]
lum_ac_codelens = [0, 2, 1, 3, 3, 2, 4, 3, 5, 5, 4, 4, 0, 0, 1, 0x7d]
lum_ac_symbols = [
0x01, 0x02, 0x03, 0x00, 0x04, 0x11, 0x05, 0x12,
0x21, 0x31, 0x41, 0x06, 0x13, 0x51, 0x61, 0x07,
0x22, 0x71, 0x14, 0x32, 0x81, 0x91, 0xa1, 0x08,
0x23, 0x42, 0xb1, 0xc1, 0x15, 0x52, 0xd1, 0xf0,
0x24, 0x33, 0x62, 0x72, 0x82, 0x09, 0x0a, 0x16,
0x17, 0x18, 0x19, 0x1a, 0x25, 0x26, 0x27, 0x28,
0x29, 0x2a, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39,
0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49,
0x4a, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59,
0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69,
0x6a, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79,
0x7a, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89,
0x8a, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98,
0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
0xa8, 0xa9, 0xaa, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6,
0xb7, 0xb8, 0xb9, 0xba, 0xc2, 0xc3, 0xc4, 0xc5,
0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xd2, 0xd3, 0xd4,
0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda, 0xe1, 0xe2,
0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9, 0xea,
0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8,
0xf9, 0xfa]
chm_dc_codelens = [0, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0]
chm_dc_symbols = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]
chm_ac_codelens = [0, 2, 1, 2, 4, 4, 3, 4, 7, 5, 4, 4, 0, 1, 2, 0x77]
chm_ac_symbols = [
0x00, 0x01, 0x02, 0x03, 0x11, 0x04, 0x05, 0x21,
0x31, 0x06, 0x12, 0x41, 0x51, 0x07, 0x61, 0x71,
0x13, 0x22, 0x32, 0x81, 0x08, 0x14, 0x42, 0x91,
0xa1, 0xb1, 0xc1, 0x09, 0x23, 0x33, 0x52, 0xf0,
0x15, 0x62, 0x72, 0xd1, 0x0a, 0x16, 0x24, 0x34,
0xe1, 0x25, 0xf1, 0x17, 0x18, 0x19, 0x1a, 0x26,
0x27, 0x28, 0x29, 0x2a, 0x35, 0x36, 0x37, 0x38,
0x39, 0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48,
0x49, 0x4a, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58,
0x59, 0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68,
0x69, 0x6a, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78,
0x79, 0x7a, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
0x88, 0x89, 0x8a, 0x92, 0x93, 0x94, 0x95, 0x96,
0x97, 0x98, 0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5,
0xa6, 0xa7, 0xa8, 0xa9, 0xaa, 0xb2, 0xb3, 0xb4,
0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xba, 0xc2, 0xc3,
0xc4, 0xc5, 0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xd2,
0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda,
0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9,
0xea, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8,
0xf9, 0xfa]
def MakeQuantHeader(p, qt, tableNo):
p.append(0xff)
p.append(0xdb) # DQT
p.append(0) # length msb
p.append(67) # length lsb
p.append(tableNo)
p.extend(qt)
def MakeHuffmanHeader(p, codelens, ncodes, symbols, nsymbols, tableNo, tableClass):
p.append(0xff)
p.append(0xc4) # DHT
p.append(0) # length msb
p.append(3 + ncodes + nsymbols) # length lsb
p.append((tableClass << 4) | tableNo)
p.extend(codelens)
p.extend(symbols)
def MakeDRIHeader(p, dri):
p.append(0xff)
p.append(0xdd) # DRI
p.append(0x0) # length msb
p.append(4) # length lsb
p.append(dri >> 8) # dri msb
p.append(dri & 0xff) # dri lsb
#===============================================================================
# Arguments:
# type, width, height: as supplied in RTP/JPEG header
# lqt, cqt: quantization tables as either derived from
# the Q field using MakeTables() or as specified
# in section 4.2.
# dri: restart interval in MCUs, or 0 if no restarts.
#
# p: pointer to return area
#
# Return value:
# The length of the generated headers.
#
# Generate a frame and scan headers that can be prepended to the
# RTP/JPEG data payload to produce a JPEG compressed image in
# interchange format (except for possible trailing garbage and
# absence of an EOI marker to terminate the scan).
#===============================================================================
def MakeHeaders(p, type, w, h, lqt, cqt, dri):
p.append(0xff)
p.append(0xd8) # SOI
MakeQuantHeader(p, lqt, 0)
MakeQuantHeader(p, cqt, 1)
if dri != 0:
MakeDRIHeader(p, dri)
p.append(0xff)
p.append(0xc0) # SOF
p.append(0) # length msb
p.append(17) # length lsb
p.append(8) # 8-bit precision
p.append(h >> 8) # height msb
p.append(h & 255) # height lsb
p.append(w >> 8) # width msb
p.append(w & 255) # wudth lsb
p.append(3) # number of components
p.append(0) # comp 0
if type == 0:
p.append(0x21) # hsamp = 2, vsamp = 1
else:
p.append(0x22) # hsamp = 2, vsamp = 2
p.append(0) # quant table 0
p.append(1) # comp 1
p.append(0x11) # hsamp = 1, vsamp = 1
p.append(1) # quant table 1
p.append(2) # comp 2
p.append(0x11) # hsamp = 1, vsamp = 1
p.append(1) # quant table 1
MakeHuffmanHeader(p, lum_dc_codelens,
len(lum_dc_codelens),
lum_dc_symbols,
len(lum_dc_symbols), 0, 0)
MakeHuffmanHeader(p, lum_ac_codelens,
len(lum_ac_codelens),
lum_ac_symbols,
len(lum_ac_symbols), 0, 1)
MakeHuffmanHeader(p, chm_dc_codelens,
len(chm_dc_codelens),
chm_dc_symbols,
len(chm_dc_symbols), 1, 0)
MakeHuffmanHeader(p, chm_ac_codelens,
len(chm_ac_codelens),
chm_ac_symbols,
len(chm_ac_symbols), 1, 1)
p.append(0xff)
p.append(0xda) # SOS
p.append(0) # length msb
p.append(12) # length lsb
p.append(3) # 3 components
p.append(0) # comp 0
p.append(0) # huffman table 0
p.append(1) # comp 1
p.append(0x11) # huffman table 1
p.append(2) # comp 2
p.append(0x11) # huffman table 1
p.append(0) # first DCT coeff
p.append(63) # last DCT coeff
p.append(0) # sucessive approx.
from struct import unpack
def list2string(l):
s = ''
for c in l:
s += chr(c)
return s
def string2list(s):
l = []
for c in s:
l.append(ord(c))
return l
class RFC2435JPEG(object):
'JPEG image recreation from RTP payload'
def __init__(self):
# Main part of these are header fields
self.TypeSpecific = 0
self.Offset = 0
self.Type = 0
self.Q = 0
self.Width = 0
self.Height = 0
self.Datagram = "" # Recieved datagram
self.JpegHeader = "" # Reconstructed header
self.JpegPayload = "" # Raw JPEG fragment
self.JpegImage = "" # Complete JPEG Image
self.QT_MBZ = 0 # Quantization Table header
self.QT_Precision = 0
self.QT_Length = 0
# These tables are put inside the JPEG header
self.QT_luma = [] # Luma table
self.QT_chroma = [] # Chroma table
self.RM_Header = '' # Restart Marker header
def loadDatagram(self, DatagramIn):
self.Datagram = DatagramIn
def parse(self):
HOffset = 0
LOffset = 0
# Straightforward parsing
(self.TypeSpecific,
HOffset, #3 byte offset
LOffset,
self.Type,
self.Q,
self.Width,
self.Height) = unpack('!BBHBBBB', self.Datagram[:8])
self.Offest = (HOffset << 16) + LOffset
self.Width = self.Width << 3
self.Height = self.Height << 3
# Check if we have Restart Marker header
if 64 <= self.Type <= 127:
# TODO: make use of that header
self.RM_Header = self.Datagram[8:12]
rm_i = 4 # Make offset for JPEG Header
else:
rm_i = 0
# Check if we have Quantinization Tables embedded into JPEG Header
# Only the first fragment will have it
if self.Q > 127 and not self.JpegPayload:
self.JpegPayload = self.Datagram[rm_i+8+132:]
QT_Header = self.Datagram[rm_i+8:rm_i+140]
(self.QT_MBZ,
self.QT_Precision,
self.QT_Length) = unpack('!BBH', QT_Header[:4])
self.QT_luma = string2list(QT_Header[4:68])
self.QT_chroma = string2list(QT_Header[68:132])
else:
self.JpegPayload += self.Datagram[rm_i+8:]
# Clear tables. Q might be dynamic.
if self.Q <= 127:
self.QT_luma = []
self.QT_chroma = []
def makeJpeg(self):
lqt = []
cqt = []
dri = 0
# Use exsisting tables or generate ours
if self.QT_luma:
lqt=self.QT_luma
cqt=self.QT_chroma
else:
MakeTables(self.Q,lqt,cqt)
JPEGHdr = []
# Make a complete JPEG header
MakeHeaders(JPEGHdr, self.Type, int(self.Width), int(self.Height), lqt, cqt, dri)
self.JpegHeader = list2string(JPEGHdr)
# And a complete JPEG image
self.JpegImage = self.JpegHeader + self.JpegPayload
self.JpegPayload = ''
self.JpegHeader = ''
self.Datagram = ''