Invalid data embedded in the QR code about qrcode HOT 13 CLOSED

Hello Steve, any update on this issue?

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Looks like it's not the data but the error correction at the root of this. I am thinking currently that the ECC bytes are overriding the data and flipping a bit in the value. Note that $7 = 0x37 and $' = 0x27

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This doesn't look trivial to get to the root of, but I have a quiet period coming up that may help me focus :)

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Steve, after verifying changes for #8 I found that L Qand H modes are working but now M mode is the only one that fails for a given string (referenced in the original post). Same problem, last character 7 is turned into '

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Yep the issue in #6 and #8 is different to this issue. There's an error correction issue that's causing a bit to flip in the data (overriding the embedded value). Further examples if you find them could perhaps be helpful.

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Ok, let me see if I can get more strings. Going to be all URL-like strings. I get them 1 in 10 (on average).

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My current hypothesis is that the ec code is causing a bit flip, so will be interesting to see if other examples could be explained by a single bit flip. I do not yet understand root cause.

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Sent you some more string over email.

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That's useful test data - thank you, Vlad. I should be able to isolate the issue and resolve it with this test data.

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Doing a few "syndrome" checks on the ECC shows that there's an error correction code generation problem... close to a solution

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Vlad, this latest update passes my testing - can you confirm with yours?

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Example production using the latest update and the original issue string (have also validated various others):

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Steve, I tried it with M error correction level and it's working great! Can be closed.

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