Different MFM image when reading from stream files

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tan1
Posts: 7
Joined: Wed Aug 22, 2018 4:06 pm

Different MFM image when reading from stream files

Post by tan1 » Sat Aug 25, 2018 12:57 pm

I've read a floppy disk with both "Kryoflux stream files, preservation" and "MFM sector image" enabled. There are 7 instances of

Code: Select all

MFM: <unformatted>
in the log file (for 7 different tracks, that is, no retries). Creating another MFM sector image from the stream files created in the step above results in only one instance of

Code: Select all

MFM: <unformatted>
but for a track that could be decoded in the first step. hxcfe can decode all tracks. What's going on there?

SomeGuy
Posts: 172
Joined: Wed Feb 18, 2015 8:18 pm

Re: Different MFM image when reading from stream files

Post by SomeGuy » Sat Aug 25, 2018 2:21 pm

Kryoflux's sector decoding is a bit pickier than other programs. It seems there are a few different things that can throw it off. If you could post the stream file someone might be able to point out specifically what the issue is in this case.

tan1
Posts: 7
Joined: Wed Aug 22, 2018 4:06 pm

Re: Different MFM image when reading from stream files

Post by tan1 » Sat Aug 25, 2018 4:25 pm

For finding out why DTC decodes data differently when reading from the disk drive vs. reading from the stream file created in parallel with decoding while reading from the disk drive, the floppy disk would be required. Anyway, I'll try to find a track that doesn't contain sensitive data.

BTW, this is a DD disk read in a HD drive at 360 RPM.

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mr.vince
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Re: Different MFM image when reading from stream files

Post by mr.vince » Thu Aug 30, 2018 5:35 pm

Correct density set?

tan1
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Joined: Wed Aug 22, 2018 4:06 pm

Re: Different MFM image when reading from stream files

Post by tan1 » Thu Aug 30, 2018 10:18 pm

Why would setting the density line affect the interpretation of the captured data? Is that setting really used by the software (rather than by the FDD)? (I usually toggle the density line after each capture.)

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mr.vince
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Re: Different MFM image when reading from stream files

Post by mr.vince » Wed Sep 05, 2018 5:40 pm

If the disk is read with the wrong density setting, it may very well happen that KryoFlux is unable to decode the data as it might have timing issues.

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