Hi, Tom, I'm not so sure I want the error concealment of the DAT machine making assumptions I can better control in Wavelab or Samplitude--but, for many transfers the error CONCEALMENT is useful and better than not using it. Archival purists might disagree. It's all a matter of the content and its potential uses. Cheers, Richard At 04:00 PM 2010-01-21, Tom Fine wrote: >Hi Richard: > >I'm aware of the difference between correction and concealment. For >usable audio, the concealment should be applied. My question was, is >it applied in a direct-to-computer system and if not is there >software to apply it so as to end up with an audio-usable copy? >Granted, digital audio is "bits is bits," but if the end result is >not usable audio, it's not very useful bits. > >-- Tom Fine > > >----- Original Message ----- From: "Richard L. Hess" ><[log in to unmask]> >To: <[log in to unmask]> >Sent: Thursday, January 21, 2010 1:40 PM >Subject: Re: [ARSCLIST] DAT ripping > > >>At 06:41 AM 2010-01-21, Tom Fine wrote: >>>Ted, I understand the point of knowing about an error. But, does >>>the tape-drive-to-computer method CORRECT the error for the >>>purpose of USING the audio? That's the whole point of >>>error-correction in the DAT machine design (and in CD players) -- >>>to make the audio stream usable to the average listener. What is >>>the point of transfer if the audio can't be used? So far no one >>>has confirmed that the direct-to-computer method provides as good >>>error correction abilities as just playing the DAT. >> >>Hi, Tom, >> >>Please do not confuse error CORRECTION and error CONCEALMENT. DAT, >>audio CD, CD-ROM, and DDS have a layer of error CORRECTION. Audio >>DAT and audio CD have an error CONCEALMENT layer AFTER the error >>CORRECTION to compensate for errors that were beyond the scope of >>the error CORRECTION. DDS and CD-ROM, I believe, both have an extra >>layer of error CORRECTION. However, this is not implemented on >>reading the audio media. >> >>In other words, both the DDS drive and the DAT player will have the >>same level of error CORRECTION for the DAT (audio) tape. The DAT >>player will add error concealment which is not necessarily what we >>want when making a preservation master. >> >>>As to Shai's point about multiple passes -- I too have had success >>>once in a while re-playing what had been a dropout. It doesn't >>>work all the time, but often enough that I'll do it with problem tapes. >> >>Yes, that can either get better or worse -- and cleaning can also help. >> >>>And yes, problem tapes can have the "error" indicator light >>>flashing constantly or on for long periods of time yet recovered >>>music stream flowing out. >> >>The "error" indicator comes on at some threshold within the >>capability of the error correction protocol in most machines. The >>Panasonic SV3800s that I have provide a four-digit error readout. >>Many machines have a two-digit error readout which is essentially >>the two left digits of the four-digit readout on the Panasonic. I >>believe this is a hexadecimal readout, but I'm not sure at the >>moment. However, on most playback of normal tapes, I get "error" >>readings up to let's say 02xx and those are all correctable. Where >>I start to hear problems are around 07xx and higher. When I made >>the tapes, I rarely saw errors as high as 0100. So any errors below >>that would not even show on a two-digit machine. I think I remember >>being upset when I saw an error into the 004x region. It stays for >>long stretches of time at 0000. >> >>>One other point -- you have the same mechanical issues with a >>>computer drive as a DAT machine, no? It's the same method of a >>>rotary head recovering data from a magnetic tape, isn't it? >> >>It's the same method of recovery, but the computer drive may (or >>may not) be more robust than the audio drive/transport. >> >>If I recall properly, there were two different drum sizes that were >>somehow made to be compatible. The porta-DATs had a drum of half >>the diameter of the studio/home machines. I'm keeping my D8 DAT >>Walkman as an alternative for recovering some tape in the future >>where this might be a benefit. >> >>At 04:14 AM 2010-01-21, Shai Drori wrote: >>>Okay, that I understand, but I am thinking about correctable >>>errors. We are then assuming that both systems will correct the >>>errors the same way since both use the schemes implemented. How do >>>we know which system has fewer errors over the other? My >>>experience with rotary head systems is that sometimes second or >>>third reading yielded better results, I think due to "cleaning" >>>actions of the previous playing. Maybe we should compare five >>>readings of the same cassette? >> >>As I understand it, the DDS tape readout software will flag any >>uncorrectable error in a log file (which I've also referred to as a >>printout). I believe it logs it by A-time. >> >>I also recall that the DDS playback method will fail if there is no >>ATIME on the tape. >> >>As to your comment about correctable errors -- who cares where >>there were correctable errors as they were corrected. All hard >>drives today have error correction and it's used regularly in normal usage. >> >>Also, don't confuse analog playback with digital playback. With >>digital, all you need to do is keep the error level within the >>correctable range and you're done. With analog, there is NO error >>correction and you need to get everything absolutely as good as you >>can. The Drop Out COMPENSATORs in analog (video) machines are the >>same as the error CONCEALMENT protocols in digital machines. >> >>In audio, our equivalent of "drop out compensators" was increasing >>tape surface area per unit time. In pro video formats there was >>little option for changing track width or tape speed. In some >>respects, that is why 15 in/s 1/2-inch 2-track with IEC >>equalization ended up being close to the ideal stereo mastering >>format for analog audio. That seems to be the point where cost, >>performance, low-frequency response, high-frequency response, >>noise, and azimuth wander are all optimized. 0.2 inch x 15 in/s is >>3 sq in/s of tape per track. Compare that to DAT or analog >>cassette...you do the math <smile>. >> >>Cheers, >> >>Richard >> >>Richard L. Hess email: [log in to unmask] >>Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX >>Detailed contact information: http://www.richardhess.com/tape/contact.htm >>Quality tape transfers -- even from hard-to-play tapes. > Richard L. Hess email: [log in to unmask] Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX Detailed contact information: http://www.richardhess.com/tape/contact.htm Quality tape transfers -- even from hard-to-play tapes.