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Re: Rescuing old tapes

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  • apendragn
    ... the web ... Is this the data?: Start = 0x0000 length= 0x0201 0000 D5 6F 64 22 F9 E0 FB F0 32 0F 76 33 60 30 01 8E 0010 52 65 22 9E FC 10 52 66 22 FF
    Message 1 of 11 , Sep 1, 2002
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      --- In cosmacelf@y..., "Gemeny, Steve" <Steve.Gemeny@j...> wrote:
      > I've posted the relevant part of the Cassette Specs. as a PDF on
      the web
      > (thanks Todd) http://mywebpages.comcast.net/aa3nm/cassette.pdf
      > <http://mywebpages.comcast.net/aa3nm/cassette.pdf>
      >
      >
      > I also posted a short WAV file that I know well as
      > http://mywebpages.comcast.net/aa3nm/elf.wav
      > <http://mywebpages.comcast.net/aa3nm/elf.wav>

      Is this the data?:

      Start = 0x0000
      length= 0x0201

      0000 D5 6F 64 22 F9 E0 FB F0 32 0F 76 33 60 30 01 8E
      0010 52 65 22 9E FC 10 52 66 22 FF 10 52 66 22 30 00
      0020 D5 6F 64 22 F9 D0 FB F0 32 2F 76 33 60 30 21 8E
      0030 52 65 22 9E FC 20 52 66 22 FF 20 52 66 22 30 20
      0040 D5 6F 64 22 F9 B0 FB F0 32 4F 76 33 60 30 41 8E
      0050 52 65 22 9E FC 40 52 66 22 FF 40 52 66 22 30 40
      0060 7B 6F 64 22 F8 04 52 66 22 F8 00 52 66 22 00 00
      0070 AC FB 84 32 C3 6F 64 22 F9 7E FB FE 3A C3 F8 00
      0080 A1 BE F8 98 B1 F8 06 AE D4 00 01 01 30 C6 8C FB
      0090 0D 32 A8 8C 7C DF 3B C3 8C 7C 81 33 C3 8C AE D4
      00A0 00 21 01 FC C0 CF 30 C3 F8 08 AE D4 00 41 01 AE
      00B0 AF 8F 32 CB C4 1E 1E 1E 1E 1E 2F 30 B1 D4 00 01
      00C0 F8 00 51 C0 01 54 FC 01 51 30 8E 9E FC 04 BE 30
      00D0 BD F8 98 B1 B2 F8 00 A1 51 F8 84 B4 B5 F8 2A A4
      00E0 F8 3C A5 F8 01 B3 F8 09 A3 F8 FF A2 E2 D3 7C 1B
      00F0 30 33 50 93 10 11 12 B1 04 83 70 31 5C 13 4E 33
      0100 30 09 00 C0 00 70 30 80 00 F8 00 AC BC BF F8 08
      0110 AF F8 01 B1 BE F8 0C AE F8 7F A1 35 1B 2E 9E 3A
      0120 1D 8C F6 7B 3D 29 7A FC 80 AC 2F 8F 32 3A F8 01
      0130 BE F8 1B AE 2E 9E 3A 34 30 21 F8 03 AF F8 01 BE
      0140 F8 1B AE 2E 9E 3A 43 7A 2F 8F 3A 3D 8C F6 73 60
      0150 64 22 30 03 AC F8 00 B1 F8 08 A1 30 62 8C F6 AC
      0160 33 63 7B F8 01 BE F8 1B AE 2E 9E 3A 69 7A 21 81
      0170 3A 5D F8 01 BE F8 59 AE 2E 9E 3A 78 30 09 00 0D
      0180 F8 00 AC F8 11 AE 3D 8B 8C F6 D5 8E F6 D5 00 00
      0190 02 8B 4E CB 4A 87 42 8B 0A 9B 6E BB 4A 8B 06 CB
      01A0 5C 31 14 31 14 17 34 53 58 19 10 33 54 3D 34 13
      01B0 64 91 54 53 64 19 74 91 56 99 14 D8 58 93 74 F3
      01C0 4A D3 8C B3 0E 71 46 DF CA 8B 4C CB 0E CB 66 0B
      01D0 26 C3 0C AB 44 B3 4D AB 4E 8B 48 EB 62 CB 8A FB
      01E0 54 73 50 13 54 11 74 9F 6C 1A 14 F7 14 07 18 0F
      01F0 50 09 74 B1 3C 39 14 11 3C 13 7C 1A 3E 19 20 1B
      0200 A4

      If so, we might have the beginnings of a technique for recovering old
      tapes.

      My program reads a wave file and generates a data file. With some
      signal processing, it might be possible to recover damaged tapes.


      Cheers,
      Art Ed LeBouthillier
    • cdp1861
      ... old ... Great timing! I just spent most of the weekend writing just such a program. My decoding routines for the data are not finished yet, but I also can
      Message 2 of 11 , Sep 2, 2002
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        > If so, we might have the beginnings of a technique for recovering
        old
        > tapes.
        >
        > My program reads a wave file and generates a data file. With some
        > signal processing, it might be possible to recover damaged tapes.

        Great timing!

        I just spent most of the weekend writing just such a program. My
        decoding routines for the data are not finished yet, but I also can
        load the WAV file now. It does not seem to make much sense to keep
        working on it if your program is already far enough to do the
        encoding.


        Richard
      • apendragn
        ... My program is not very sophisticated; I basically just did a low pass filter, differentiate the signal, overdrive and measure the pulse width. I had tried
        Message 3 of 11 , Sep 2, 2002
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          > I just spent most of the weekend writing just such a program. My
          > decoding routines for the data are not finished yet, but I also can
          > load the WAV file now. It does not seem to make much sense to keep
          > working on it if your program is already far enough to do the
          > encoding.

          My program is not very sophisticated; I basically just did a low pass
          filter, differentiate the signal, overdrive and measure the pulse
          width.

          I had tried all sorts of filtering techniques but they kept adding
          artifacts that corrupted the data. Still, I think a correlation
          technique would be useful for poor quality tapes. I'm still working
          on this.

          Cheers,
          Ed LeBouthillier
        • cdp1861
          Well, I ll keep on working. The other way around, constructing a WAV file from binary data, certainly seems to be the lesser part. To decode the recorded WAV
          Message 4 of 11 , Sep 2, 2002
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            Well, I'll keep on working. The other way around, constructing a WAV
            file from binary data, certainly seems to be the lesser part. To
            decode the recorded WAV files I thought of using a low and a high
            threshold value to recognize the high and low parts. Given the
            sampling rate there should be a certain number of samples in a row
            above or below the corresponding threshold. Problems could be the
            transitions which could result in samples which are inbetween the
            two thresholds. I planned to make the two threshold values variable
            in order to adjust to different recording levels.

            My WAV routines are at the moment only for 8 bit mono recordings
            without compression. The sampling rate is free, but should not be
            below 20 kHz.

            Good luck
            Richard
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