I'm not very familiar with telecom or radio protocols, but I think the extra information in an LTE packet (the parity bits + redundant data bits) might be critical to that sort of error correction working. The raw PCM coming out of an optical drive doesn't provide that kind of metadata, so at best I can count how many values appear at each position and try to guess on that. If the values after 20 rips look like this:
CD1 position 0xFFFF
A0: XXXXXXXXXXXXXXX
A1: XXX
A2: XX
CD2 position 0xFFFF
A0: XX
A1: XXX
A2: XXXXXXXXXXXXXXX
then I'm not sure how any sort of combining could usefully recover the original value.
You have to look at the effect of the noise on the statistics of the bits, since those are what's physically changing, and not the PCM output after all the error correction layers.
> You have to look at the effect of the noise on the statistics of the bits,
Yes. Soft combining (in systems designed for it) isn't even done on bits, it's done on the actual analog (well, a digitised version of the analog value, sometimes termed a "log likelihood ratio") values of the signal in question -- before any quantisation happens.
This isn't to say that you can't apply the techniques here (where stuff obviously gets quantised unless you can find a way to get the raw signal from the photodiodes), but you need access to bits with the least amount of error-correction involved (or find a way to infer what the statistics of the original raw bits are from what the decoding machinery outputs).
