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• I'm trying to hide information in a H264 video. When I stitch the video up, split it into frames again and try to read it, the information is lost

  18 mai 2024, par Wer Wer

  I'm trying to create a video steganography python script. The algorithm for hiding will be...

  


  

  1. convert any video codec into h264 lossless

  


  2. save the audio of the video and split the h264 video into frames

  


  3. hide my txt secret into frame0 using LSB replacement method

  


  4. stitch the video back up and put in the audio

  


  


  ...and when I want to recover the text, I'll

  


  

  1. save the audio of the video and split the encoded h264 video into frames

  


  2. retrieve my hidden text from frame0 and print the text

  


  


  So, this is what I can do :

  


  

  1. split the video

  


  2. hide the text in frame0

  


  3. retrieve the text from frame0

  


  4. stitch the video

  


  


  But after stitching the video, when I tried to retrieve the text by splitting that encrypted video, it appears that the text has been lost. This is because i got the error

  


  UnicodeEncodeError: &#x27;charmap&#x27; codec can&#x27;t encode character &#x27;\x82&#x27; in position 21: character maps to <undefined>&#xA;</undefined>

  


  I'm not sure if my LSB replacement algorithm was lost, which results in my not being able to retrieve my frame 0 information, or if the H264 conversion command I used was a converted my video into H264 lossy version instead of lossless (which I don't believe so because I specified -qp 0)
This was the command I used to convert my video

  


  ffmpeg -i video.mp4 -t 12 -c:v libx264 -preset veryslow -qp 0 output.mp4


  


  These are my codes

  


  import json
import os
import magic
import ffmpeg
import cv2
import numpy as np

import subprocess

# Path to the file you want to check
here = os.path.dirname(os.path.abspath(__file__))
file_path = os.path.join(here, "output.mp4")
raw_video = cv2.VideoCapture(file_path)
audio_output_path = os.path.join(here, "audio.aac")
final_video_file = os.path.join(here, "output.mp4")

# create a folder to save the frames.
frames_directory = os.path.join(here, "data1")
try:
    if not os.path.exists(frames_directory):
        os.makedirs(frames_directory)
except OSError:
    print("Error: Creating directory of data")

file_path_txt = os.path.join(here, "hiddentext.txt")
# Read the content of the file in binary mode
with open(file_path_txt, "r") as f:
    file_content = f.read()
# txt_binary_representation = "".join(format(byte, "08b") for byte in file_content)
# print(file_content)

"""
use this cmd to convert any video to h264 lossless. original vid in 10 bit depth format
ffmpeg -i video.mp4 -c:v libx264 -preset veryslow -qp 0 output.mp4

use this cmd to convert any video to h264 lossless. original vid in 8 bit depth format
ffmpeg -i video.mp4 -c:v libx264 -preset veryslow -crf 0 output.mp4

i used this command to only get first 12 sec of video because the h264 vid is too large 
ffmpeg -i video.mp4 -t 12 -c:v libx264 -preset veryslow -qp 0 output.mp4

check for multiple values to ensure its h264 lossless:
1. CRF = 0
2. qp = 0
3. High 4:4:4 Predictive
"""


# region --codec checking. ensure video is h264 lossless--
def check_h264_lossless(file_path):
    try:
        # Use ffprobe to get detailed codec information, including tags
        result = subprocess.run(
            [
                "ffprobe",
                "-v",
                "error",
                "-show_entries",
                "stream=codec_name,codec_long_name,profile,level,bit_rate,avg_frame_rate,nb_frames,tags",
                "-of",
                "json",
                file_path,
            ],
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE,
            text=True,
        )
        # Check if the file is lossless
        metadata = check_h264_lossless(file_path)
        print(json.dumps(metadata, indent=4))

        # Check if the CRF value is available in the tags
        for stream in metadata.get("streams", []):
            if stream.get("codec_name") == "h264":
                tags = stream.get("tags", {})
                crf_value = tags.get("crf")
                encoder = tags.get("encoder")
                print(f"CRF value: {crf_value}")
                print(f"Encoder: {encoder}")
        return json.loads(result.stdout)
    except Exception as e:
        return f"An error occurred: {e}"


# endregion


# region --splitting video into frames--
def extract_audio(input_video_path, audio_output_path):
    if os.path.exists(audio_output_path):
        print(f"Audio file {audio_output_path} already exists. Skipping extraction.")
        return
    command = [
        "ffmpeg",
        "-i",
        input_video_path,
        "-q:a",
        "0",
        "-map",
        "a",
        audio_output_path,
    ]
    try:
        subprocess.run(command, check=True)
        print(f"Audio successfully extracted to {audio_output_path}")
    except subprocess.CalledProcessError as e:
        print(f"An error occurred: {e}")


def split_into_frames():
    extract_audio(file_path, audio_output_path)
    currentframe = 0
    print("Splitting...")
    while True:
        ret, frame = raw_video.read()
        if ret:
            name = os.path.join(here, "data1", f"frame{currentframe}.png")
            # print("Creating..." + name)
            cv2.imwrite(name, frame)
            currentframe += 1
        else:
            print("Complete")
            break


# endregion


# region --merge all back into h264 lossless--
# output_video_file = "output1111.mp4"


def stitch_frames_to_video(frames_dir, output_video_path, framerate=60):
    command = [
        "ffmpeg",
        "-y",
        "-framerate",
        str(framerate),
        "-i",
        os.path.join(frames_dir, "frame%d.png"),
        "-c:v",
        "libx264",
        "-preset",
        "veryslow",
        "-qp",
        "0",
        output_video_path,
    ]

    try:
        subprocess.run(command, check=True)
        print(f"Video successfully created at {output_video_path}")
    except subprocess.CalledProcessError as e:
        print(f"An error occurred: {e}")


def add_audio_to_video(video_path, audio_path, final_output_path):
    command = [
        "ffmpeg",
        "-i",
        video_path,
        "-i",
        audio_path,
        "-c:v",
        "copy",
        "-c:a",
        "aac",
        "-strict",
        "experimental",
        final_output_path,
    ]
    try:
        subprocess.run(command, check=True)
        print(f"Final video with audio created at {final_output_path}")
    except subprocess.CalledProcessError as e:
        print(f"An error occurred: {e}")


# endregion


def to_bin(data):
    if isinstance(data, str):
        return "".join([format(ord(i), "08b") for i in data])
    elif isinstance(data, bytes) or isinstance(data, np.ndarray):
        return [format(i, "08b") for i in data]
    elif isinstance(data, int) or isinstance(data, np.uint8):
        return format(data, "08b")
    else:
        raise TypeError("Type not supported")


def encode(image_name, secret_data):
    image = cv2.imread(image_name)
    n_bytes = image.shape[0] * image.shape[1] * 3 // 8
    print("[*] Maximum bytes to encode:", n_bytes)
    secret_data += "====="
    if len(secret_data) > n_bytes:
        raise ValueError("[!] Insufficient bytes, need bigger image or less data")
    print("[*] Encoding Data")

    data_index = 0
    binary_secret_data = to_bin(secret_data)
    data_len = len(binary_secret_data)
    for row in image:
        for pixel in row:
            r, g, b = to_bin(pixel)
            if data_index < data_len:
                pixel[0] = int(r[:-1] + binary_secret_data[data_index], 2)
                data_index += 1
            if data_index < data_len:
                pixel[1] = int(g[:-1] + binary_secret_data[data_index], 2)
                data_index += 1
            if data_index < data_len:
                pixel[2] = int(b[:-1] + binary_secret_data[data_index], 2)
                data_index += 1
            if data_index >= data_len:
                break
    return image


def decode(image_name):
    print("[+] Decoding")
    image = cv2.imread(image_name)
    binary_data = ""
    for row in image:
        for pixel in row:
            r, g, b = to_bin(pixel)
            binary_data += r[-1]
            binary_data += g[-1]
            binary_data += b[-1]
    all_bytes = [binary_data[i : i + 8] for i in range(0, len(binary_data), 8)]
    decoded_data = ""
    for byte in all_bytes:
        decoded_data += chr(int(byte, 2))
        if decoded_data[-5:] == "=====":
            break
    return decoded_data[:-5]


frame0_path = os.path.join(here, "data1", "frame0.png")
encoded_image_path = os.path.join(here, "data1", "frame0.png")


def encoding_function():
    split_into_frames()

    encoded_image = encode(frame0_path, file_content)
    cv2.imwrite(encoded_image_path, encoded_image)

    stitch_frames_to_video(frames_directory, file_path)
    add_audio_to_video(file_path, audio_output_path, final_video_file)


def decoding_function():
    split_into_frames()
    decoded_message = decode(encoded_image_path)
    print(f"[+] Decoded message: {decoded_message}")


# encoding_function()
decoding_function()



  


  So I tried to put my decoding function into my encoding function like this

  


  def encoding_function():
    split_into_frames()

    encoded_image = encode(frame0_path, file_content)
    cv2.imwrite(encoded_image_path, encoded_image)

#immediately get frame0 and decode without stitching to check if the data is there
    decoded_message = decode(encoded_image_path)
    print(f"[+] Decoded message: {decoded_message}")

    stitch_frames_to_video(frames_directory, file_path)
    add_audio_to_video(file_path, audio_output_path, final_video_file)



  


  This returns my secret text from frame0. But splitting it after stitching does not return my hidden text. The hidden text was lost

  


  def decoding_function():
    split_into_frames()
#this function is after the encoding_function(). the secret text is lost, resulting in charmap codec #can't encode error
    decoded_message = decode(encoded_image_path)
    print(f"[+] Decoded message: {decoded_message}")


  


  EDIT :
So i ran the encoding function first, copied frame0.png out and placed it some where. Then I ran the decoding function, and got another frame0.png.

  


  I ran both frame0.png into this python function

  


  frame0_data1_path = os.path.join(here, "data1", "frame0.png")
frame0_data2_path = os.path.join(here, "data2", "frame0.png")
frame0_data1 = cv2.imread(frame0_data1_path)
frame0_data2 = cv2.imread(frame0_data2_path)

if frame0_data1 is None:
    print(f"Error: Could not load image from {frame0_data1_path}")
elif frame0_data2 is None:
    print(f"Error: Could not load image from {frame0_data2_path}")
else:

    if np.array_equal(frame0_data1, frame0_data2):
        print("The frames are identical.")
    else:
        print("The frames are different.")


  


  ...and apparently both are different. This means my frame0 binary got changed when I stitch back into the video after encoding. Is there a way to make it not change ? Or will h264 or any video codec change a little bit when you stitch the frames back up ?

  


• On ALAC’s Open Sourcing

  1er novembre 2011, par Multimedia Mike — Codec Technology

  Apple open sourced their lossless audio codec last week. Pretty awesome ! I have a theory that, given enough time, absolutely every codec will be open source in one way or another.

  I know I shouldn’t bother reading internet conversation around any news related to multimedia technology. And if I do read it, I shouldn’t waste any effort getting annoyed about them. But here are some general corrections :

  • ALAC is not in the same league as — nor is it a suitable replacement for — MP3/AAC/Vorbis or any other commonly used perceptual audio codec. It’s not a matter of better or worse ; they’re just different families of codecs designed for different purposes.
  • Apple open sourced ALAC, not AAC– easy mistake, though there’s nothing to ‘open source’ about AAC (though people can, and will, argue about its absolute ‘open-ness’).
  • There’s not much technical room to argue between ALAC and FLAC, the leading open source lossless audio compressor. Both perform similarly in terms of codec speeds (screamingly fast) and compression efficiency (results vary slightly depending on source material).
  • Perhaps the most frustrating facet is the blithe ignorance about ALAC’s current open source status. While this event simply added an official “open source” status to the codec, ALAC has effectively been open source for a very long time. According to my notes, the ALAC decoding algorithm was reverse engineered in 2005 and added into FFmpeg in March of the same year. Then in 2008, Google — through their Summer of Code program — sponsored an open source ALAC encoder.

  From the multimedia-savvy who are versed in these concepts, the conversation revolves around which would win in a fight, ALAC or FLAC ? And who between Apple and FFmpeg/Libav has a faster ALAC decoder ? The faster and more efficient ALAC encoder ? I contend that these issues don’t really matter. If you have any experience working with lossless audio encoders, you know that they tend to be ridiculously fast to both encode and decode and that many different lossless codecs compress at roughly the same ratios.

  As for which encoder is the fastest : use whatever encoder is handiest and most familiar, either iTunes or FFmpeg/Libav.

  As for whether to use FLAC or ALAC — if you’ve already been using one or the other for years, keep on using it. Support isn’t going to vanish. If you’re deciding which to use for a new project, again, perhaps choose based on software you’re already familiar with. Also, consider hardware support– ALAC enjoys iPod support, FLAC is probably better supported in a variety of non-iPod devices, though that may change going forward due to this open sourcing event.

  For my part, I’m just ecstatic that the question of moral superiority based on open source status has been removed from the equation.

  Code-wise, I’m interested in studying the official ALAC code to see if it has any corner-case modes that the existing open source decoders don’t yet account for. The source makes mention of multichannel (i.e., greater than stereo) configurations, but I don’t know if that’s in FFmpeg/Libav.

• Remove avserver.

  9 juin 2014, par Anton Khirnov

  Remove avserver.
  It has not been properly maintained for years and there is little hope
  
  of that changing in the future.
  
  It appears simpler to write a new replacement from scratch than
  
  unbreaking it.
  

  • [DBH] .gitignore
  • [DBH] Changelog
  • [DBH] Makefile
  • [DBH] avserver.c
  • [DBH] configure
  • [DBH] doc/avserver.conf
  • [DBH] doc/avserver.texi
  • [DBH] doc/general.texi
  • [DBH] libavformat/Makefile
  • [DBH] libavformat/allformats.c
  • [DBH] libavformat/ffm.h
  • [DBH] libavformat/ffmdec.c
  • [DBH] libavformat/ffmenc.c
  • [DBH] tests/fate/avformat.mak
  • [DBH] tests/fate/seek.mak
  • [DBH] tests/lavf-regression.sh
  • [DBH] tests/ref/lavf/ffm
  • [DBH] tests/ref/seek/lavf-ffm