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Re: Cassette to MP3 Converter

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  • somaspack
    MP3 is lossy, maybe ok for music but bad for must-have bits. Scott
    Message 1 of 13 , Jul 11, 2013
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      MP3 is lossy, maybe ok for music but bad for must-have bits.

      Scott

      --- In cosmacelf@yahoogroups.com, Egan Ford <datajerk@...> wrote:
      >
      > My experience with Apple II cassettes as MP3 has been not very
      > successful. I am 100% successful with WAV or AIFF (uncompressed
      > formats).
    • Egan Ford
      ... No, but if you go to comp.sys.apple2 or http://www.applefritter.com/forum/84 and ask you ll get a rapid response. Heavy traffic in both places.
      Message 2 of 13 , Jul 11, 2013
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        > Off topic but are you familiar with Apple 2 DOS 3.2 (or earlier?).
        > I'm specifically looking for the 5/3 nibble routine.

        No, but if you go to comp.sys.apple2 or
        http://www.applefritter.com/forum/84 and ask you'll get a rapid
        response. Heavy traffic in both places.

        Alternatively you can try Beneath Apple DOS. DOS 3.1 - 3.3 is covered
        in there (http://asciiexpress.net/files/docs/).

        Cheers,

        Egan
      • joshbensadon
        HI Egan, Thanks! I ll go try applefritter. I ve already read Beneath Apple DOS . Very good book on the floppy disk software, but falls a little short in the
        Message 3 of 13 , Jul 12, 2013
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          HI Egan,

          Thanks! I'll go try applefritter.

          I've already read "Beneath Apple DOS". Very good book on the floppy disk software, but falls a little short in the ordering of the 5/3 nibbilizer. I also read "Understanding the Apple II" by Jim Sather. It does a fantastic job at explaining the hardware and Woz's floppy controller. Woz essentially built his own microcoded state machine.

          In "Beneath Apple DOS" they show you where to nibbilize the first 5 bytes but not the next 5, so you have to still "Guess" the pattern. Guessing isn't the sort of thing you like to do when writting code.

          But thanks again for the great advice!

          :)J


          --- In cosmacelf@yahoogroups.com, Egan Ford <datajerk@...> wrote:
          >
          > > Off topic but are you familiar with Apple 2 DOS 3.2 (or earlier?).
          > > I'm specifically looking for the 5/3 nibble routine.
          >
          > No, but if you go to comp.sys.apple2 or
          > http://www.applefritter.com/forum/84 and ask you'll get a rapid
          > response. Heavy traffic in both places.
          >
          > Alternatively you can try Beneath Apple DOS. DOS 3.1 - 3.3 is covered
          > in there (http://asciiexpress.net/files/docs/).
          >
          > Cheers,
          >
          > Egan
          >
        • Kevin
          ... MP3 is garbage for music too. ;)
          Message 4 of 13 , Jul 12, 2013
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            > MP3 is lossy, maybe ok for music but bad for must-have bits.

            MP3 is garbage for music too. ;)
          • Ray Sills
            True, MP3 is lossy. But, that may not matter when you are trying to record or reproduce two tones that are frequency shift keyed to designate encode a
            Message 5 of 13 , Jul 13, 2013
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              True, MP3 is lossy. But, that may not matter when you are trying to
              record or reproduce two tones that are frequency shift keyed to
              designate encode a sequence of 1s and 0s. You certainly do not -
              need- to "compress" (data reduce) the content for a 4K binary file.
              Even using AIFF or WAV files won't create very large files, especially
              by today's standards where 4K is the smallest size file stored on a
              modern HD... at least on my iMac.

              The FSK tones usually used are well in the normal voice frequency
              (telephone quality) spectrum. And, the tape format is normally quite
              tolerant of frequency variations caused by wow and flutter or off-
              speed that might be expected in a cheap cassette machine. I know that
              the RCA VIP used frequencies of 800 Hz and 2000 Hz to differentiate
              the data 1s and 0s. The VIP tape format output 4 seconds of 2000 Hz
              tone as a header to synchronize the tape read routines, followed by
              2.5 seconds of varying tones per 256 byte block (page). Bytes always
              start with a 1 start bit, followed by 8 data bits, and end with a
              parity bit.. (odd parity).

              So, my take on it is that while MP3 offers no huge advantage, it
              should be OK for saving and loading data. That said, I have not tried
              it, and it would be an interesting experiment to see how it might work
              or not work.

              73 de Ray



              On Jul 11, 2013, at 3:38 PM, somaspack wrote:

              > MP3 is lossy, maybe ok for music but bad for must-have bits.
              >
              > Scott
            • bill rowe
              My original thought was that this thing probably depended on pc software for the mp3 conversion and you could maybe get it to save a wav file instead for input
              Message 6 of 13 , Jul 13, 2013
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                My original thought was that this thing probably depended on pc software for the mp3 conversion and you could maybe get it to save a wav file instead for input to richard's conversion tool.

                On 2013-07-13, at 12:45 PM, "Ray Sills" <raysills3@...> wrote:

                 

                True, MP3 is lossy. But, that may not matter when you are trying to
                record or reproduce two tones that are frequency shift keyed to
                designate encode a sequence of 1s and 0s. You certainly do not -
                need- to "compress" (data reduce) the content for a 4K binary file.
                Even using AIFF or WAV files won't create very large files, especially
                by today's standards where 4K is the smallest size file stored on a
                modern HD... at least on my iMac.

                The FSK tones usually used are well in the normal voice frequency
                (telephone quality) spectrum. And, the tape format is normally quite
                tolerant of frequency variations caused by wow and flutter or off-
                speed that might be expected in a cheap cassette machine. I know that
                the RCA VIP used frequencies of 800 Hz and 2000 Hz to differentiate
                the data 1s and 0s. The VIP tape format output 4 seconds of 2000 Hz
                tone as a header to synchronize the tape read routines, followed by
                2.5 seconds of varying tones per 256 byte block (page). Bytes always
                start with a 1 start bit, followed by 8 data bits, and end with a
                parity bit.. (odd parity).

                So, my take on it is that while MP3 offers no huge advantage, it
                should be OK for saving and loading data. That said, I have not tried
                it, and it would be an interesting experiment to see how it might work
                or not work.

                73 de Ray

                On Jul 11, 2013, at 3:38 PM, somaspack wrote:

                > MP3 is lossy, maybe ok for music but bad for must-have bits.
                >
                > Scott

              • joshbensadon
                ... Hi Ray, I feel the same way, but, like you, I have not experimented with it so I don t know for sure. I agree with your basic argument which is these
                Message 7 of 13 , Jul 13, 2013
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                  --- In cosmacelf@yahoogroups.com, Ray Sills <raysills3@...> wrote:
                  >
                  > So, my take on it is that while MP3 offers no huge advantage, it
                  > should be OK for saving and loading data. That said, I have not tried
                  > it, and it would be an interesting experiment to see how it might work
                  > or not work.

                  Hi Ray,

                  I feel the same way, but, like you, I have not experimented with it so I don't know for sure. I agree with your basic argument which is these compilations are nothing more than ONE signal of two alternating tones. I can't see how MP3 can mess that up. Now here comes the big "BUT". The human ear is very forgiving, in fact, I'm sure we can still hear a song playing even after you turn off the audio (or are those just the voices in my head?). My point is, perhaps MP3 at some point starts adding new transitions on the signal? It might be convenient to skip a phase transition just to create a pattern. That skip might not be heard by the human ear, but apparently ELF ears are much keener.

                  It would definitely be a fun experiment, I will also conduct the same one here... some day. MP3 comes in different degrees of compression, so that will likely have an impact?

                  Up to now, I've heard the masses on line saying it doesn't work, so I have to bow to those pioneers that have already tried it.

                  :)J
                • Egan Ford
                  ... The tones are not relevant, at least that is the case for the Apple II. All that is measured is the number of cycles between zero crossings. The default
                  Message 8 of 13 , Jul 13, 2013
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                    > True, MP3 is lossy. But, that may not matter when you are trying to
                    > record or reproduce two tones that are frequency shift keyed to
                    > designate encode a sequence of 1s and 0s.

                    The tones are not relevant, at least that is the case for the Apple
                    II. All that is measured is the number of cycles between zero
                    crossings. The default for the Apple II is 1000 Hz for a 0 and 2000
                    Hz for a 1. It's up to the programmer to count the cycles to
                    determine 0 or 1 (and there is always a + or - to consider).

                    > So, my take on it is that while MP3 offers no huge advantage, it
                    > should be OK for saving and loading data. That said, I have not tried
                    > it, and it would be an interesting experiment to see how it might work
                    > or not work.

                    I've download and used MP3s that work just fine with the Apple II,
                    OTOH the ones that I have created have been hit or miss (probably some
                    setting). I speculate that the lossy compression may alter the
                    waveform and skip some of the zero crossings. Depending on how
                    tolerant the programmer was with ranges for 0 and 1 may determine if
                    they work. The 1000 Hz/2000 Hz range is fairly tolerant to issues
                    with different tape players, volume, tape stretch, etc... so I agree
                    is might work.

                    For my asciiexpress.net project I created my own audio code using 6000
                    Hz/12000 Hz to up the default 1333 bps to 8000 bps (I also threw in
                    compression to get 2x more on average). On some machines I can push
                    the native rate to 9600 bps, but it does not work on all machines--I
                    think have reached the tolerances of the HW design. MP3 for this
                    higher frequency download code hasn't worked out. Between data
                    compression and using higher frequency the AIFF/WAV files are smaller
                    as well further reducing any advantage of MP3 size.

                    I think another issue I may have encountered with MP3 was the player
                    and how the player did the D2A. It's been about 2 years since I
                    explored MP3 as an option, but I recall getting different results with
                    different players. AIFF/WAV have universally worked. I didn't take
                    very good notes, I was just trying to get results.

                    Lastly, I wonder if taking an original tape with all of its analog
                    glory and doing tape to MP3 may work better. I wonder if that is how
                    most of the MP3s that have worked for me were created. I create my
                    own files as "perfect" waveforms using a tool I wrote to convert
                    binary code to audio. That audio when converted to MP3 was
                    problematic. Again it could just be my tight 8000-9600 bps
                    requirements. And again, poor note taking.

                    Cheers,

                    Egan
                  • bill rowe
                    asciiexpress.net is very cool. You can select any of a bunch of apple programs and stream them into the cassette port of your apple from your phone.
                    Message 9 of 13 , Jul 13, 2013
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                      asciiexpress.net is very cool. You can select any of a bunch of apple programs and stream them into the cassette port of your apple from your phone.


                      On 2013-07-13, at 7:12 PM, "Egan Ford" <datajerk@...> wrote:

                       

                      > True, MP3 is lossy. But, that may not matter when you are trying to
                      > record or reproduce two tones that are frequency shift keyed to
                      > designate encode a sequence of 1s and 0s.

                      The tones are not relevant, at least that is the case for the Apple
                      II. All that is measured is the number of cycles between zero
                      crossings. The default for the Apple II is 1000 Hz for a 0 and 2000
                      Hz for a 1. It's up to the programmer to count the cycles to
                      determine 0 or 1 (and there is always a + or - to consider).

                      > So, my take on it is that while MP3 offers no huge advantage, it
                      > should be OK for saving and loading data. That said, I have not tried
                      > it, and it would be an interesting experiment to see how it might work
                      > or not work.

                      I've download and used MP3s that work just fine with the Apple II,
                      OTOH the ones that I have created have been hit or miss (probably some
                      setting). I speculate that the lossy compression may alter the
                      waveform and skip some of the zero crossings. Depending on how
                      tolerant the programmer was with ranges for 0 and 1 may determine if
                      they work. The 1000 Hz/2000 Hz range is fairly tolerant to issues
                      with different tape players, volume, tape stretch, etc... so I agree
                      is might work.

                      For my asciiexpress.net project I created my own audio code using 6000
                      Hz/12000 Hz to up the default 1333 bps to 8000 bps (I also threw in
                      compression to get 2x more on average). On some machines I can push
                      the native rate to 9600 bps, but it does not work on all machines--I
                      think have reached the tolerances of the HW design. MP3 for this
                      higher frequency download code hasn't worked out. Between data
                      compression and using higher frequency the AIFF/WAV files are smaller
                      as well further reducing any advantage of MP3 size.

                      I think another issue I may have encountered with MP3 was the player
                      and how the player did the D2A. It's been about 2 years since I
                      explored MP3 as an option, but I recall getting different results with
                      different players. AIFF/WAV have universally worked. I didn't take
                      very good notes, I was just trying to get results.

                      Lastly, I wonder if taking an original tape with all of its analog
                      glory and doing tape to MP3 may work better. I wonder if that is how
                      most of the MP3s that have worked for me were created. I create my
                      own files as "perfect" waveforms using a tool I wrote to convert
                      binary code to audio. That audio when converted to MP3 was
                      problematic. Again it could just be my tight 8000-9600 bps
                      requirements. And again, poor note taking.

                      Cheers,

                      Egan

                    • jdripper
                      ... And _Beneath Apple DOS_ is flat-out wrong when they claim that there are clock bits between the bits of the nibble. The whole point of using GCR is that
                      Message 10 of 13 , Jul 15, 2013
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                        --- In cosmacelf@yahoogroups.com, "joshbensadon" <joshbensadon@...> wrote:
                        > I've already read "Beneath Apple DOS". Very good book on the floppy disk software, but falls a little short in the ordering of the 5/3 nibbilizer.

                        And _Beneath Apple DOS_ is flat-out wrong when they claim that there are clock bits between the bits of the nibble. The whole point of using GCR is that it is self-clocking, so it doesn't need to throw away half the bandwidth on clock bits the way that normal single-density (FM) encoding does. That's why Apple gets 13 or 16 256-byte sectors per track where competing systems using single density only got 10 256-byte sectors.

                        The 4+4 nibblization of the address mark contents is FM, a degenerate case of GCR.

                        Normal double-density (MFM) encoding is even more efficient that Apple's GCR, for a given channel bandwidth, but requires more hardware than the Apple design, and more precise discrimination of the time between flux changes. To be any good, MFM requires a phase-locked-loop for recovery. The state machine of the Apple floppy controller includes a crude state machine, but not good enough for reliable MFM.

                        For many years, hard drives usually used (1,7) or (2,7) RLL, which is a form of GCR that is even more efficient than MFM, but requires an even better data separator. Now most hard drives use even more complex coding than that.

                        Eric
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