output mismatching when porting a python from python2 env to python3 env

[prayuktibid]

I am porting a python code which was written in python2 into the latest python3.8. I made some minor changes in syntax without changing the main logic such that it could run in the python3 environment without error. Both codes running correctly but the outputs are a little bit different from each other.

I thought I have made some mistakes that is why python3 code giving a different output. I have tried my best but I didn't find any mistake by myself.

I have posted below both python2 and python3 code. My humble request to please help me to find my error in python3 code.

Python2 code

    
import json

capture_settings= [{"framerate": 30, "width": 1280, "height": 720, "bitrate": 17000000, "overlay": False, "gop_size": 30}]

SEI_UUID_CAMERA_SETTINGS = bytearray(b'\x08\x94\xfc\xa2\x58\xce\x45\x02\x8f\x18\xc0\x8c\x68\xe5\x32\x35')
#print(len(SEI_UUID_CAMERA_SETTINGS))
#""" encode values >= 255 as 0xff0xff..0xresidual """
def encode_multibyte_value(value):
    """ encode values >= 255 as 0xff0xff..0xresidual """

    encoded = bytearray()

    while (value >= 255):
        encoded += bytearray(chr(255))
        value -= 255

    encoded += bytearray(chr(value))

    return encoded

def escape_bytearray(input):
    """ escape 000 to 0030, 001 to 0031, 002 to 0032 and 003 to 0033 """
    output = bytearray()

    history1 = None
    history2 = None

    for b in input:
        if (history1==0) and (history2==0) and (b <= 3):
            output += chr(3)
            history1 = 3
            history2 = b
        else:
            history1 = history2
            history2 = b

        output += chr(b)    

    return output


def create_sei_nal_unit(uuid, payload_string):
    """ create a 'user data unregistered' SEI nal unit in a bytearray """

    assert(bytearray == type(uuid))
    print(uuid)

    uuid_length = len(uuid)
    assert(16 == uuid_length)   

    nal_unit_prefix = bytearray(b'\x00\x00\x00\x01')
    nal_unit_type = bytearray(chr(6))                   # 6 = SEI

    encoded_payload_type = encode_multibyte_value(5)    # 5 = 'user data unregistered'

    payload = bytearray(payload_string)

    encoded_payload_size = encode_multibyte_value(uuid_length + len(payload))
    print(uuid + payload)
    escaped_payload = escape_bytearray(uuid + payload)


    trailing_bits = bytearray(b'\x80')

    sei_nal_unit = ( nal_unit_prefix
                   + nal_unit_type
                   + encoded_payload_type
                   + encoded_payload_size
                   + escaped_payload
                   + trailing_bits )

    return sei_nal_unit

sei_nal_unit = create_sei_nal_unit(SEI_UUID_CAMERA_SETTINGS, json.dumps(capture_settings))
print(sei_nal_unit)

Output:

x���X�E���h�25[{"overlay": false, "gop_size": 30, "framerate": 30, "height": 720, "width": 1280, "bitrate": 17000000}]�

Python3 Code:

 
import json


capture_settings= [{"framerate": 30, "width": 1280, "height": 720, "bitrate": 17000000, "overlay": False, "gop_size": 30}]

SEI_UUID_CAMERA_SETTINGS = b'\x08\x94\xfc\xa2\x58\xce\x45\x02\x8f\x18\xc0\x8c\x68\xe5\x32\x35'
#print(len(SEI_UUID_CAMERA_SETTINGS))
#""" encode values >= 255 as 0xff0xff..0xresidual """
def encode_multibyte_value(value):
    """ encode values >= 255 as 0xff0xff..0xresidual """

    encoded = bytes()

    while (value >= 255):
        encoded += bytes(chr(255).encode('utf-8'))
        value -= 255

    encoded += bytes(chr(value).encode('utf-8'))

    return encoded

def escape_bytearray(input):
    """ escape 000 to 0030, 001 to 0031, 002 to 0032 and 003 to 0033 """
    output = bytes()

    history1 = None
    history2 = None

    for b in input:
        if (history1==0) and (history2==0) and (b <= 3):
            output += b'\x03'
            history1 = 3
            history2 = b
        else:
            history1 = history2
            history2 = b

        output += chr(b).encode('utf-8')    

    return output


def create_sei_nal_unit(uuid, payload_string):
    """ create a 'user data unregistered' SEI nal unit in a bytearray """

    assert(bytes == type(uuid))

    uuid_length = len(uuid)
    assert(16 == uuid_length)   

    nal_unit_prefix = b'\x00\x00\x00\x01'
    nal_unit_type = b'\x06'                  # 6 = SEI
    encoded_payload_type = encode_multibyte_value(5)    # 5 = 'user data unregistered'

    payload = bytes(payload_string)

    encoded_payload_size = encode_multibyte_value(uuid_length + len(payload))
    escaped_payload = escape_bytearray(uuid + payload)


    trailing_bits = b'\x80'

    sei_nal_unit = ( nal_unit_prefix
                   + nal_unit_type
                   + encoded_payload_type
                   + encoded_payload_size
                   + escaped_payload
                   + trailing_bits )

    return sei_nal_unit

sei_nal_unit = create_sei_nal_unit(SEI_UUID_CAMERA_SETTINGS, json.dumps(capture_settings).encode('utf-8'))
print(sei_nal_unit)

Output:

b'\x00\x00\x00\x01\x06\x05x\x08\xc2\x94\xc3\xbc\xc2\xa2X\xc3\x8eE\x02\xc2\x8f\x18\xc3\x80\xc2\x8ch\xc3\xa525[{"framerate": 30, "width": 1280, "height": 720, "bitrate": 17000000, "overlay": false, "gop_size": 30}]\x80'