aacRepair - Full documentation

repair aac and aacPlus files grabbed from the internet

![Tests](https://github.com/44xtc44/aacRepair/actions/workflows/tests.yml/badge.svg?branch=dev)

Info

AAC files consist of multiple segments, frames. Each frame has a header and a payload. Browser gets stuck if AAC file frame is defective and will not start to play or refuse to play next AAC file. This will stop the entire playlist. File gets trimmed from head to tail, to remove defective frames. Cut off byte count is shown in the summary.

Note

Self documenting code is (docStrings) short and read by document builder tools. –> aacrepair package

Command Line

$ aacrepair

        Menu "Main"
1 -- Single File aac or aacPlus
2 -- Bulk Repair, Folder
3 -- Exit
Enter your choice: 1

Python or sys.path fail; use

$ python -m aacrepair.cmd

aacrepair Module

bulk repair

from aacrepair import AacRepair

# 'r' before a string tells the Python interpreter to treat backslashes as a literal (raw) character
aacRepair = AacRepair(r"F:\propaganda-podcasts")
# setter overrides default export path 'F:\propaganda-podcasts\aac_repair'
aacRepair.set_export_path(r"F:\repaired_foobar")
aacRepair.repair()
Instantiate AacRepair class with two possible arguments, mandatory folder path and optional dictionary.

  1. No dictionary provided. Folder path is used as list to import files into a dictionary AND store repaired files.

  2. A dictionary of files is provided. Folder path is used to store repaired files. (best use on web server)

Web Server

  • Endpoint converts multi-file upload from file storage type to bytestream, uses .read() method

  • List of files is written to dictionary {file_name_key: file_byte_content_value}

  • web server gets not the file path, only file name - needs path to store repaired files

  • dictionary {file(n).aac: b’x65x66x67x00x10x00x00x00x04x00’}

code:

files = request.files.getlist('fileUploadAcpRepair')
f_dict = {f: open(f, "rb").read() for f in files if f[-5:] == ".aacp" or f[-4:] == ".aac"}
aacRepair = AacRepair("/home/Kitty/aac_files", f_dict)
aacRepair.repair()
File System

  • List of files in folder is written to dictionary {file_name_key: file_byte_content_value}

code:

aacRepair = AacRepair("/home/Kitty/meow_aac")
aacRepair.set_export_path("/home/Kitty/foo")
aacRepair.repair()

single object

head and tail are used to cut chunks left or right only

aacRepair = AacRepair()
# converts file path to file content, if object is not of type bytes
rep_object = aacRepair.repair_object(aac_path_or_object, head=None, tail=None)

header_aac Module

Use as input for further aac stream processing or repair.

from aacrepair import header_aac

header_aac module example to show all frames with header.

header_aac.pull_frame('/home/foo/bar.aac')

header_aac dictionary output of header_info(aac_object, frame_bytes=None, print_out=True)

SYNC_WORD_BOOL: True
MPEG4_BOOL: True
Layer_BOOL: True
CRC_16_IS_SET_BOOL: False
PROFILE_INT: 1
PROFILE_STR: AAC Main
SAMPLING_FREQUENCY_INT: 3
SAMPLING_FREQUENCY_STR: 48000 Hz
PRIVATE_BIT_BOOL: False
CHANNEL_CONFIG_INT: 2
CHANNEL_CONFIG_STR: 2 channels: front-left, front-right
ORIGINALITY_BOOL: False
HOME_BOOL: False
COPYRIGHT_ID_INT: 0
COPYRIGHT_START_INT: 0
FRAME_LENGTH_INT: 530
BIT_RESERVOIR_INT: 2047
FRAME_NUMBER_INT: 0
CRC_16: {}
IS_LAST_FRAME_BOOL: False
ERROR_STR:
FRAME_BYTES: b''

Bytes

1

2

3

4

5

6

7

8

9

AAAAAAAA

AAAABCCD

EEFFFFGH

HHIJKLMM

MMMMMMMM

MMMOOOOO

OOOOOOPP

QQQQQQQQ

QQQQQQQQ

Bit Groups

Group

Number

Count

Description

A

0-12

12

Syncword, all bits 1

B

13

1

MPEG Version set 0 is MPEG-4, set 1 MPEG-2

C

14-15

2

Layer set to 0

D

16

1

[[[ Warning ]]], set to 1 if there is no CRC and 0 if there is CRC

E

17-18

2

Profile, the MPEG-4 Audio Object Type https://en.wikipedia.org/wiki/MPEG-4_Part_3

F

19-22

4

MPEG-4 Sampling Frequency https://wiki.multimedia.cx/index.php/MPEG-4_Audio

G

23

1

Private bit set to 0,

H

24-26

3

MPEG-4 Channel Configuration https://wiki.multimedia.cx/index.php/MPEG-4_Audio

I

27

1

Originality, set 1 originality of audio, else 0

J

28

1

Home, set to 1 to signal home usage of the audio, else 0

K

29

1

Copyright ID bit

L

30

1

Copyright ID start

M

31-43

13

Frame length of ADTS frame including headers and CRC check - 1

O

44-54

11

Buffer fullness, states the bit-reservoir per frame

P

55-56

2

Number of AAC ADTS frame minus 1

Q

57-72

16

CRC check

pip install

""" Linux """
$ pip3 install aacrepair

""" Windows """
> pip install aacrepair

Uninstall

Python user

  • find the module location

  • uninstall and then remove remnants

remove:

>$ pip3 show aacrepair
>$ pip3 uninstall aacrepair

Location: … /python310/site-packages

What’s next - contributions welcome

  • try multithread a test

  • multiprocessing plus multithreading repair, if file count is x (works only on linux)

  • android ‘Threading in Worker’, make it run