tancik / StegaStamp

Invisible Hyperlinks in Physical Photographs
http://www.matthewtancik.com/stegastamp
MIT License
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How high can ‘bit_acc’ reach without BCH code? #31

Closed LeeeLiu closed 3 years ago

LeeeLiu commented 3 years ago

Hello, tancik!

  1. Excuse me, if you don't use BCH code, what is the decoding accuracy (bit_acc)?

  2. Every 12 bytes (96 bits), only 5 bits can be corrected, right?

    • In encode_image.py and decode_image.py, The BCH parameters you use are:
      BCH_POLYNOMIAL = 137
      BCH_BITS = 5
    • According to the bchlib source code, my understanding is, The entire packet can only be corrected by 5 bits, right? In your case, packet is 12 bytes (96 bits), data is 7 bytes (56 bits, embedded link length)
tancik commented 3 years ago
  1. Table 1 of the paper has a breakdown of bit accuracy for different camera / printer pairs - https://arxiv.org/abs/1904.05343
  2. Yep, you are correct.
LeeeLiu commented 3 years ago

Oh, I see. Your reply is very helpful. Thanks!

---Original--- From: "Matthew Tancik"<notifications@github.com> Date: 2021/1/5 06:45:44 To: "tancik/StegaStamp"<StegaStamp@noreply.github.com>; Cc: "Author"<author@noreply.github.com>;"LeeeLiu"<lily516@foxmail.com>; Subject: Re: [tancik/StegaStamp] How high can ‘bit_acc’ reach without BCH code? (#31)

Table 1 of the paper has a breakdown of bit accuracy for different camera / printer pairs - https://arxiv.org/abs/1904.05343

Yep, you are correct.

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