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Comment by jhallenworld | Hacker News Reader

Actually I have a related question about CDs: do any CD players indicate when the (Reed-Solomon I think) forward error correction actually corrects any errors? This could give an indication of the quality of the media. It could be total corrected error count, or corrected error count per minute.. something like that.

Second, do any give an indication of when the error correction fails: I think CD players just fill the missing data with the last sample value (certainly this was the case for first gen CD players)- but this FLAC encoding gives a better procedure: replace the missing samples from those of a predictive model. But either way, it would be nice to know when the playback is not perfect.

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As to your second question:

> Some ROM drives are capable of reporting C2 error information along with the audio data and some ripping software can use this information to determine whether the retrieved audio data is valid or not. A standardised mechanism for ROM drives to report C2 error information is documented in the Multi-Media Command (MMC) standard

https://docs.linn.co.uk/wiki/index.php/CD_Ripping_Terminolog...

My experience backing up up audio cds with Exact Audio Copy tells me that CD players have limited error correction facilities and using EAC is the only way to know! (read retail CD brand new get same as reference checksum, read same CD ten years later, mismatch errors popup on a few tracks), the FAQ on EAC gives some details on CD player capabilities - standalone audio CD players use oversampling and more but most don't tell you when it kicks in - there's typically only one small LCD/LED line of display. https://www.exactaudiocopy.de/en/index.php/support/faq/

Well this gives me an idea for an interesting FPGA project. The early CD players, like Sony D-5 (I just looked at its service manual), have accessible recovered clock and data signals (they are buried in a chip for newer devices). It would not be too hard to make the EFM decoder, de-interleaver, and error corrector in an FPGA so that I can have these features.

How much would audiophiles pay to have a quality indicator on their CD player? Hmm...

Edit: Sony's CXD2500BQ shows error correction information on the pins- no FPGA needed.

CXD2500BQ is used in Onkyo's DX-7310

This company claims to have a product for this (but no pictures..), follow the links for their "CD Errormonitor":

https://www.wpnsystems.com/

> there's typically only one small LCD/LED line of display.

Still-- why not just output Quake on that line and subtract the error correction from the starting 100% health?

Many years ago (> 25) a friend's cd player showed this information, I think it was a denon.

I've never personally seen that on a dedicated player (appliance nor software), I assume because they are more interested in keeping the music playing.

Exact Audio Copy shows it but will spend minutes re-reading the same frames: https://i.imgur.com/ZGozdhz.png (screenshot mine, unfortunately)

If you’re somewhat lucky, you’ll be able to repair it with CueTools via CTDB.

cdparanoia [1], also from Xiph, reports (and attempts to correct) such errors.

[1] https://www.xiph.org/paranoia/

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