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Re: audio to .tzx conversion: a "lost bit" issue?

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>>>>> Fred  <fredm@spamcop.net> writes:
>>>>> Ivan Shmakov <oneingray@gmail.com> wrote:

 >> Any idea what may be happening there, or what else could I try?

 > It's important to get as much signal to noise as possible.  Try
 > recording with the volume just short of clipping as just using sox to
 > increase volume alone will also increase noise.

	This makes sense, although the whole problem with clipping is
	that you don't know it have occurred until after the fact.  So,
	I've tried to allow for some "headroom" while digitizing the
	records, just in case the volume would suddenly rise in the
	middle of the tape.

	Also, I've tried two more cassette players I was able to find
	around here, and stopped on the last of them.  So far, I was
	able to successfully produce a few .tzx'es.  (Well, at the
	least, the software appears to load fine from these.  I guess I
	should check the data against the WoS archive, as some of the
	software on these cassettes could also be found there.)

	Two more factors are that I've tried the other cassettes I have
	(so perhaps those I've tried initially were faulty), and that
	I've applied a bandpass filter (as per SoX' "sinc 640-13440"),
	as otherwise the sync pulse was failing to cross the zero line
	more than just occasionally.  Also, this levels the amplitudes
	of the frequencies used somewhat.

	(BTW, is it a feature of ZX tape records that the higher of
	these frequencies has noticeable lower amplitude than that of
	the lower one?  Or is it my hardware's fault?  One more issue
	with that is that the signal's "trail" may be of amplitude
	almost matching that of the higher frequency, so that
	audio2tape(1) considers it an extra bit; which, naturally, makes
	the number of bits in the stream, sans the sync pulse and the
	parity bit, not divisible by 8.)

 > Could you post the wav somewhere so others can have a look and try as
 > well?

	I guess so, should I ran into issues once again.

-- 
FSF associate member #7257

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Thread

audio to .tzx conversion: a "lost bit" issue? Ivan Shmakov <oneingray@gmail.com> - 2013-01-17 19:36 +0000
  Re: audio to .tzx conversion: a "lost bit" issue? "Brian Gaff" <Briang1@blueyonder.co.uk> - 2013-01-18 09:14 +0000
    Re: audio to .tzx conversion: a "lost bit" issue? Ivan Shmakov <oneingray@gmail.com> - 2013-01-18 19:41 +0000
      Re: audio to .tzx conversion: a "lost bit" issue? "Daniel Mandic" <daniel_mandic@hotmail.com> - 2013-01-18 20:13 +0000
  Re: audio to .tzx conversion: a "lost bit" issue? Fred <fredm@spamcop.net> - 2013-01-18 06:53 -0600
    Re: audio to .tzx conversion: a "lost bit" issue? Ivan Shmakov <oneingray@gmail.com> - 2013-01-21 08:59 +0000
      Re: audio to .tzx conversion: a "lost bit" issue? Fred <fredm@spamcop.net> - 2013-01-22 14:52 -0600

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