Help! How do I fix this problem?

Discussion in 'rec.audio.pro' started by Druhms, Aug 26, 2003.

  1. Druhms

    Druhms Guest

    A lady brought in a cassette tape of a deposition wanting me to fix it. She
    described the problem to me as her tape was dragging and it needed speeding up
    so she could understand the words. Well, I listen to it and it is much worse
    than a simple thing like that. It sounds as if her machine went crazy. It
    sounds like it has been run through a hardcore chorus with the rate at full
    speed. I don't know what caused this. Within one short word it goes from
    super slow to super fast about 400 times. Horrible warble sound. Can't make
    out anything anyone is saying. Does anyone have any pointers on this? Maybe
    some software that can fix this? I can't imagine there being a quick fix.
    Seems like the only way to fix it would be to take it word by word andslow down
    and speed up each sweep....which would be rediculous. It is very unpredictable
    too, so it isn't like you could put on the effect to counter the effect
    already there. I hope I'm explaining this well.
    Thanks for the help everyone.
    JJ
  2. axtogrind

    axtogrind Guest

    This isn't a rec.audio.pro response, but it may help. Usually the most
    effecient solution isn't what the client came in looking for. If you tell
    her that you estimate it will cost $5,000 for you to go through and recreate
    word for word, or whatever you would charge for all that time, you might
    discover that she has other sources for the information: for example, is
    that the 'original' of the tape? Was there not a reporter / stenographer
    present at the time? (Is there a stenographer's tape of the transcript that
    was typed at the time.) It is VERY unusual for a deposition to be recorded
    on cassette with NO OTHER means of recording. I know some state offices
    that do it in my state, of very short (10 - 15 minute) depositions, but that
    is it.

    'Cause if it is important enough to depose someone, it is important enough
    to hire a court reporter.

    So if you DON'T get any good tech responses here, you might just have to
    give her a minute by minute quote...

    Keith

    "Druhms" <druhms@aol.com> wrote in message
    news:20030825213712.27902.00000605@mb-m29.aol.com...
    > A lady brought in a cassette tape of a deposition wanting me to fix it.

    She
    > described the problem to me as her tape was dragging and it needed

    speeding up
    > so she could understand the words. Well, I listen to it and it is much

    worse
    > than a simple thing like that. It sounds as if her machine went crazy.

    It
    > sounds like it has been run through a hardcore chorus with the rate at

    full
    > speed. I don't know what caused this. Within one short word it goes from
    > super slow to super fast about 400 times. Horrible warble sound. Can't

    make
    > out anything anyone is saying. Does anyone have any pointers on this?

    Maybe
    > some software that can fix this? I can't imagine there being a quick fix.
    > Seems like the only way to fix it would be to take it word by word andslow

    down
    > and speed up each sweep....which would be rediculous. It is very

    unpredictable
    > too, so it isn't like you could put on the effect to counter the effect
    > already there. I hope I'm explaining this well.
    > Thanks for the help everyone.
    > JJ
  3. "Druhms" <druhms@aol.com> wrote in message
    news:20030825213712.27902.00000605@mb-m29.aol.com...
    > A lady brought in a cassette tape of a deposition wanting me to fix it.

    She
    > described the problem to me as her tape was dragging and it needed

    speeding up
    > so she could understand the words. Well, I listen to it and it is much

    worse
    > than a simple thing like that. It sounds as if her machine went crazy.

    It
    > sounds like it has been run through a hardcore chorus with the rate at

    full
    > speed. I don't know what caused this. Within one short word it goes from
    > super slow to super fast about 400 times. Horrible warble sound. Can't

    make
    > out anything anyone is saying. Does anyone have any pointers on this?

    Maybe
    > some software that can fix this?


    I don't know squat about this, but I seem to remember a discussion here or
    in the Pro Audio newslist of a possible solution. If you assume the bias
    frequency was relatively constant, then you could use it to control the
    playback speed. How you actually do this is left as an exercise for the
    reader, as this mechanical engineer doesn't have a clue.

    Jerry Steiger
  4. W. Williams

    W. Williams Guest

    I've seen this happen with really cheap tape recorders when they start to
    malfunction. The occasions I have seen this tape actually speeds up at
    random and when recording and then slows down to normal speed, although your
    example appears to be more extreme.

    I have successfully restored short selections (up to 20 minutes), using the
    pitch bend function in Sound Forge, to something approaching useable,
    although artefacts are unavoidable. Most WAV editing software will have a
    similar function. This is a pretty time-consuming exercise and should only
    be undertaken if it is fairly short or it is a really important and your
    client is prepared to pay for a less than ideal final product. You could
    offer to try a short section of say a minute, see if you are able to obtain
    acceptable results, and then extrapolate a quote for the entire file.

    You basically have to get the best possible recording you can to your PC for
    editing in your software of choice (16/44 should be fine). The method I use
    is to work in small sections starting from the beginning of the file. Look
    for the first "normal" spot and then select the area up to that point - I
    like to create regions, but markers will work just as well. Open your pitch
    bend function (usually found under the effects menu) and then manually add,
    preview and adjust envelope points until your selection sounds acceptable.
    Then you update the file and repeat the process.

    My experience was that generally the audio would rapidly increase in pitch
    till it reached a specific point, where it would remain constant for a few
    seconds before decreasing in the same manner. This results in the envelope
    having a more or less \___/ shape. This will obviously be inverted if you
    have to increase the pitch.

    I hope my understanding of your problem is correct and, if so, that you have
    some success.

    W

    "Druhms" wrote:

    > A lady brought in a cassette tape of a deposition wanting me to fix it.

    She
    > described the problem to me as her tape was dragging and it needed

    speeding up
    > so she could understand the words. Well, I listen to it and it is much

    worse
    > than a simple thing like that. It sounds as if her machine went crazy.

    It
    > sounds like it has been run through a hardcore chorus with the rate at

    full
    > speed. I don't know what caused this. Within one short word it goes from
    > super slow to super fast about 400 times. Horrible warble sound. Can't

    make
    > out anything anyone is saying. Does anyone have any pointers on this?

    Maybe
    > some software that can fix this? I can't imagine there being a quick fix.
    > Seems like the only way to fix it would be to take it word by word andslow

    down
    > and speed up each sweep....which would be rediculous. It is very

    unpredictable
    > too, so it isn't like you could put on the effect to counter the effect
    > already there. I hope I'm explaining this well.
    > Thanks for the help everyone.
    > JJ
  5. Scott Dorsey

    Scott Dorsey Guest

    Druhms <druhms@aol.com> wrote:
    >A lady brought in a cassette tape of a deposition wanting me to fix it. She
    >described the problem to me as her tape was dragging and it needed speeding up
    >so she could understand the words. Well, I listen to it and it is much worse
    >than a simple thing like that. It sounds as if her machine went crazy. It
    >sounds like it has been run through a hardcore chorus with the rate at full
    >speed. I don't know what caused this. Within one short word it goes from
    >super slow to super fast about 400 times. Horrible warble sound. Can't make
    >out anything anyone is saying. Does anyone have any pointers on this? Maybe
    >some software that can fix this? I can't imagine there being a quick fix.
    >Seems like the only way to fix it would be to take it word by word andslow down
    >and speed up each sweep....which would be rediculous. It is very unpredictable
    >too, so it isn't like you could put on the effect to counter the effect
    >already there. I hope I'm explaining this well.
    >Thanks for the help everyone.


    So, it's rapid warble? Is it all in recording, or is it also in playback?
    If you watch the tape path, is anything bouncing around? Does she have the
    original machine that it was made with so you can take it apart and see what
    was originally going on?
    --scott

    --
    "C'est un Nagra. C'est suisse, et tres, tres precis."
  6. P Stamler

    P Stamler Guest

    And to add to Scott's question, have you transplanted the tape to a new
    cassette with new slip-sheets and pressure pad, and did that make any
    difference?

    Peace,
    Paul
  7. "W. Williams" <W.Williams@HotPOP.com> wrote in message
    news:1061896210.668915@skink.ru.ac.za...

    > Open your pitch bend function (usually found under the effects menu) and

    then manually add,
    > preview and adjust envelope points until your selection sounds acceptable.
    > Then you update the file and repeat the process.


    If it's happening 400 times a word (which I'm pretty sure is an extreme
    rustication) that wouldn't even if you have the patience to do it.
  8. Druhms

    Druhms Guest

    Thanks everyone for your responses, and to answer Scott's questions, it is a
    very fast warble. I'm assuming it is in playback. It was recorded onto the
    tape like this by her machine. I admit I am exagerating when I say 400 times
    per word, but more realistically about 80 times per word. Very fast. I would
    think it would be very painful going through and fixing 30 minutes of this
    with a pitch control device in Pro Tools or Sound Forge. I was hoping there
    was some restoration plug in or some trick that a forensics person may use.
    Thanks again,
    JJ



    >So, it's rapid warble? Is it all in recording, or is it also in playback?
    >If you watch the tape path, is anything bouncing around? Does she have the
    >original machine that it was made with so you can take it apart and see what
    >was originally going on?
    >--scott
    >
    >--
    >"C'est un Nagra. C'est suisse, et tres, tres precis."
  9. Scott Dorsey

    Scott Dorsey Guest

    Druhms <druhms@aol.com> wrote:
    >Thanks everyone for your responses, and to answer Scott's questions, it is a
    >very fast warble. I'm assuming it is in playback. It was recorded onto the
    >tape like this by her machine.


    Is it in playback or is it only in recording? If it's also in playback,
    you can fix that. But if it's only on the recording, you can't do anything
    about that.

    >I admit I am exagerating when I say 400 times
    >per word, but more realistically about 80 times per word. Very fast. I would
    >think it would be very painful going through and fixing 30 minutes of this
    >with a pitch control device in Pro Tools or Sound Forge. I was hoping there
    >was some restoration plug in or some trick that a forensics person may use.


    No, but there might be a way to fix it if it's a mechanical issue that is
    only on playback, and if it's a mechanical issue on recording you can at
    least see what is going on to see about undoing it. Does the pressure pad
    bounce when you play it back?
    --scott
    >



    --
    "C'est un Nagra. C'est suisse, et tres, tres precis."
  10. Mike Rivers

    Mike Rivers Guest

    In article <20030826164755.02751.00000367@mb-m23.aol.com> druhms@aol.com writes:

    > Thanks everyone for your responses, and to answer Scott's questions, it is a
    > very fast warble. I'm assuming it is in playback. It was recorded onto the
    > tape like this by her machine.


    Sounds like the recorder was momentarily slowing down, practically
    stopping. When played back at a reasonably constant speed, it would
    sound like a rapid rise in pitch.

    > but more realistically about 80 times per word. Very fast. I would
    > think it would be very painful going through and fixing 30 minutes of this
    > with a pitch control device in Pro Tools or Sound Forge.


    So what's wrong with a little pain if you're going to be well paid for
    it? This sort of thing doesn't get done automagically. And forensics
    restorers get very well paid. Try a bit and see how much time it takes
    you to make a couple of sentences listenable, then give your client a
    quote for the job. All she can do is say "no thanks."




    --
    I'm really Mike Rivers - (mrivers@d-and-d.com)
  11. Druhms <druhms@aol.com> wrote:
    > A lady brought in a cassette tape of a deposition wanting me to fix it. She
    > described the problem to me as her tape was dragging and it needed speeding
    > up so she could understand the words. Well, I listen to it and it is much
    > worse than a simple thing like that. It sounds as if her machine went
    > crazy. It sounds like it has been run through a hardcore chorus with the
    > rate at full speed. I don't know what caused this. Within one short word
    > it goes from super slow to super fast about 400 times. Horrible warble
    > sound. Can't make out anything anyone is saying. Does anyone have any
    > pointers on this? Maybe some software that can fix this? I can't imagine
    > there being a quick fix. Seems like the only way to fix it would be to
    > take it word by word andslow down and speed up each sweep....which would
    > be rediculous. It is very unpredictable too, so it isn't like you could
    > put on the effect to counter the effect already there. I hope I'm
    > explaining this well.


    I would start by transfering the tape to a new shell to ensure it is not
    a friction problem on playback, then if that doesn't work it gets
    interesting...

    Digitise the signal directly off the tape playback head with a FAST ADC,
    (you want the capture the bias signal), the lock a software PLL with
    a reasonably wide lockup range and a loop bandwidth sufficient to track
    the speed variations to the bias signal, use the control loop signal to
    control your playout speed. You could also of course do this in the
    hardware domain with electronics built on a bit of veroboard and
    with the control loop acting as a servo loop controlling the motor
    speed..
    Removing the flywheel on the playback deck will make the loop
    stability problem more manageable.

    A fair bit of work in C/Fortran/Matlab or whatever your weapon of choice
    is for this sort of computer play but it MAY be doable....

    I have done similar things with old 1/2 inch reel to reel video
    (Tape baking wouldn't fix it, and the speed was very variable, fixed by
    measuring the actual time between line sync pulses then resampling the
    line to fit).

    Regards, Dan.
    --
    ** The email address *IS* valid, do NOT remove the spamblock
    And on the evening of the first day the lord said...........
    ..... LX 1, GO!; and there was light.
  12. Mike Rivers

    Mike Rivers Guest

    In article <u82mib.ms.ln@spamblock.demon.co.uk> dmills@spamblock.demon.co.uk writes:

    > I would start by transfering the tape to a new shell to ensure it is not
    > a friction problem on playback, then if that doesn't work it gets
    > interesting...


    Too late for that. Since the description of the problem was that it
    gets "super fast" on playback, unless there's a serious problem in the
    playback deck, the damage was done on recording - the tape slowed down
    when it was recorded, so that when played back at the correct speed,
    it speeds up.

    I don't think there's any automatic way to fix this problem. That's
    why this sort of work is very expensive (or it's done by people who
    regret taking on the job).



    --
    I'm really Mike Rivers - (mrivers@d-and-d.com)
  13. Mike Rivers

    Mike Rivers Guest

    In article <tkotib.7i2.ln@spamblock.demon.co.uk> dmills@spamblock.demon.co.uk writes:

    > I still think you could use the bias to control a servo loop.


    I suppose you could, but then you'd have to build a transport that can
    respond to speed changes that quickly. You'd probably have better luck
    with something like generating a "speed" track, and then writing a
    pitch shift algorithm that takes its imput from the speed.

    Some FM instrumentation recorders use the carrier frequency to derive
    a flutter compensation sigal. Flutter, when the FM is demodulated,
    manifests itself as amplitude noise.


    --
    I'm really Mike Rivers - (mrivers@d-and-d.com)

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