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Does repeated destructive editing of lossless file degrade the file?

Discussion in 'Mastering' started by SyntheticThought, Aug 19, 2018.

?

Will this degrade the sound of the file?

  1. Yes it will degrade it.

    0 vote(s)
    0.0%
  2. No, why would it?

    1 vote(s)
    100.0%
  1. SyntheticThought

    SyntheticThought Active Member

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    (To be clear, I'm not asking if repeated copying of a WAV degrades the file. I know the answer to that is no.)

    So, if I paste a bunch of WAV masters into, let's say, SoundForge, to sequence an album after mixing and mastering....And I do dozens of tiny cuts in volume, raises in volume, removing small spaces, adding silence between tracks, AND I HIT "SAVE" AFTER EACH little edit, will it degrade the file?

    I know people will say "you should do that in a project file of a non-destructive NLE program", but I prefer destructive editing for this. Particularly Sound Forge.

    If I do 120 cuts and saves in a 90-minute long, 24-bit, 44.1k stereo WAV file, will it degrade the overall audio at all?

    I Googled a bunch of things and couldn't find the answer anywhere, at least not from people who seemed to know what they were talking about.

    I figured y'all here would know for sure one way or the other. :synth:rockoutabduction

    Thank you!
     
  2. Boswell

    Boswell Moderator Distinguished Member

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    There's more than one implied question in your post.

    Firstly, saving and recalling a .wav file does not alter its content. This is a primary advantage in editing using a digital system over bouncing a track to analogue tape.

    Beyond that, it's up to the DAW (or whatever tool is being used for digital editing) as to whether it makes changes to the waveform in areas that are not expressly being edited. This may raise some eyebrows, but early versions of some well-known DAWs were not bit-perfect, for example, performing conversions between 24-bit integer and 32-bit floating point on every load and save.

    One further process that was not always trustworthy was using a DAW to copy ADAT or S/PDIF source streams to a .wav file. A few years back I Investigated whether digital data was always bit-accurate, as I had found that there could be small differences in the .wav files saved by different DAWs copying the same digital source. I went painstakingly through the source code of the half-dozen or so DAWs I could find that were open-source and determined that, of them, only Audacity definitely could made perfect copies of a stereo S/PDIF source. I then used the Audacity files to compare the captured .wav files written by some commercial DAWs, and this is when I found they were not all bit-accurate. That said, it was a few years ago, and it's entirely probable that the most recent versions of all DAWs have corrected this problem.

    So the answer to your question about audio degradation after 120 cuts and saves is that it's likely, but not certain, that there will be no degradation when using a quality DAW. However, Sound Forge was not one of the DAWs I investigated.

    As a secondary point, hitting "save" after each edit is a worthy precaution against either equipment failure or the operator making an unintended edit. Each save would be over-written by the next one, assuming each edit was judged successful. That means that only the last version would survive, so it does not matter how many saves took place along the way.
     
    SyntheticThought and Kurt Foster like this.
  3. pcrecord

    pcrecord Quality recording seeker ! Distinguished Member

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    Boswell will correct me but here is what I think :
    Doing cuts on a track isn't destructive in most DAW because the original file isn't modified. When you do process (freeze, mixdown, etc) the track then it is replaced by another file. So if you would do this 120times while reloading the new file each time. I suspect the quality could be degraded depending on the DAW, as Boswell explained.

    But I if you do all your cuts on the track of the daw but no freeze mixdown etc.. the only possible degradation level will be when you will export the project. It is unlikely that the quality will be degraded with a one time export. Of course, going from 24bit to 16bit is a degradation by itself.

    Where it would be bad for the quality is if eachtime you hit save, a new audio .wav file was created and not just the project file which should always refer to the same original file...
    I know that Izotope RX can do this, it can save by replacing the file or save as a new file. Unfortunatly I don't use Sound Forge to confirm if it's different. But hit save as and check if it's a project file or saving directly in .wav you should have your answer.

    After all that discussion, may I suggest using automation instead of actual track cutting ?
     
  4. SyntheticThought

    SyntheticThought Active Member

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    Thank you.
    I got an answer elsewhere, someone told me to do a Null Test.

    I did, and confirmed that it did NOT alter the file, at least not in SoundForge. And yes, it does make a new WAV and delete the original each time you do that in SoundForge. That is what "destructive editing" is. Unlike in, most DAWS, and also in non-SoundForge wave editors, like Audacity. Audacity makes a project file, and you have to render a new file to make a file with your changes.

    Long conversation on this same topic, with some screenshots of the results from the Null Test, are here:
    https://www.gearslutz.com/board/ele...ctive-editing-lossless-file-degrade-file.html

    Video on doing a Null Test:
     
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  5. Boswell

    Boswell Moderator Distinguished Member

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    Goodness, that was painful. It's really difficult to watch videos given by people who don't have a solid understanding of the topic they are trying to put over.
     
    pcrecord likes this.
  6. SyntheticThought

    SyntheticThought Active Member

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    I actually didn't watch it. Just thought a video would help. I'd love to edit and put in a better link or video, but I can't edit. Is that something you have to post here a while to be able to do?

    Edit: Ah, I see. Editing times out after the post is up for a while.

    I learned Null Test from someone posting this:

    "Look up Null Test if you don't know how to do it (it's easy). Then get your original audio, put a heap of cuts in, but no actual changes so that it remains time-locked with the original (if that makes sense). Then do the null test: ie invert the audio, put it in another track to play back with the original, and you should get exactly no signal (no sound), if and only if your edits did not degrade (ie., change) the original audio."
     
  7. paulears

    paulears Well-Known Member

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    The way I see it, clones of digital data are absolutely identical. If you change something in the file, it is no longer identical and will sound different. Minutely? Perhaps even better, but certainly different.

    If you drop the level of say, the bell tree the drummer played, and then save the file, it has been changed. Load it back in and boost the bell tree and the only data you have is from the highest level it reached (which is lower than the original) and zero. The dynamic range of the instrument is much more limited. The lowest levels will come up, and that of course is where the system noise in the original was, but low enough not to be heard. Upping the top, raises the bottom noisy bit - which could be heard in a sparse mix.

    Digital levels can be played with ONLY when the DAW has access to the full data stream. If you have limited this, you cannot get it back. That's how it works in real life. Digital has an amazing range from zero to full, but once you limit it, and then save - the only way to get it back is to reload the old file.
     
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  8. SyntheticThought

    SyntheticThought Active Member

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    In theory, yes.

    Issue is, that some wave editors, it turns out, introduce minute variance when making the new master file during each save in destructive editing.

    I actually tested this with a Null Test, and Sound Forge does NOT do this.

    Long conversation on this same topic, with some screenshots of the results from the Null Test, are here:
    https://www.gearslutz.com/board/ele...ctive-editing-lossless-file-degrade-file.html

    I'm going to ask the Admin to let me edit my OP here to add that info, otherwise people will be answering this on gut feeling forever when it's already settled science. lol.
     
  9. SyntheticThought

    SyntheticThought Active Member

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    Boswell, can you please grant me one-time permission to edit my OP post here? Basically here's why, as I replied above to paulears. I won't change anything in my post, just add "EDIT", the date, and the info below, in the bottom of the thread. Otherwise this thread becomes a huge time suck for everyone, forever.

    I can do this without permission on most forums.

    If you can't allow me to do that, can you lock the thread maybe?

    Here's what I'd add:
    =--=
    EDIT, Aug 21, 2018:
    Some wave editors, it turns out, introduce minute variance when making the new master file during each save in destructive editing.

    I actually tested this with a Null Test, and Sound Forge does NOT do this.
    Long conversation on this same topic, with some screenshots of the results from the Null Test, are here:
    https://www.gearslutz.com/board/ele...ctive-editing-lossless-file-degrade-file.html

    I'm going to ask the Admin to let me edit my OP here to add that info, otherwise people will be answering this on gut feeling forever when it's already settled science. lol.
     
  10. Boswell

    Boswell Moderator Distinguished Member

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    You are flogging a dead horse here, unwittingly, I suspect, egged on by a few of the tunnel-visioned contributers to the similar thread you started over at GS. I see little point in editing a previous post, less still of locking the thread.

    The title you gave the thread here on RO was
    "Does repeated destructive editing of lossless file degrade the file?" The problem is that it's at best a title that is open to varied interpretation, and at worst is self-contradictory. You've had a range of replies giving different views on the topic, and there's not a lot more to say.

    If you are really asking is whether some audio editors make changes at the bit level to parts of an audio file that you have not intentionally edited, then that's already been covered, starting with my post tagged as #2 above, and is expressly not implied by your title.

    On occasions when I've been invited to give lectures on audio topics, one of the demonstrations I sometimes do is to put up on the big screen a pair of waveforms that are clearly very different when examined in detail. This is demonstrated by then displaying the output of a null test between the files, which shows significant differences. When I play the two files one after the other, they sound identical. They are, in fact, recordings of the same source sampled both directly and through a 90 degree all-pass phase shifter. The point here is that analysis of digital waveforms only illustrates half a story, and it's easy to get carried away with the visuals while neglecting the audio. That's not to say that there isn't a point in performing digital analysis, and the sort of area where such analysis is useful is to check on things we have mentioned above, such as serial degradation of a source through rounding decisions caused by unnecessary format conversions.
     
  11. SyntheticThought

    SyntheticThought Active Member

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    Totally uncalled for. I'm just trying to learn, man. Your whole tone is overreacting to me simply asking a question.

    Yeah, I'm out. y'all here are prickly.

    Gearslutz forums are much more active, are far more friendly, and from what I can tell, a good bit smarter and less ego in the answers.

    Deleting my account here. Or just blocking y'all as spam on gmail if I can't delete it.

    Good luck with continuing to chase good people out of your quiet party.


    Bye, Felecia!
     
  12. paulears

    paulears Well-Known Member

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    I've taken a piece of piano classical music into Sound Forge. I have then saved it back out as a new file. I have then reloaded it and applied the smallest amount of eq it would allow at 100Hz, and reserved it as v1. I then removed that track, reloaded it fresh and removed the smallest amount of eq I could at 100Hz, and reserved it, then closed the file. I repeated it 10 times.

    The results with these files are the same on Cubase and Sound Forge. The original, in mono, 100% nulls the original version with polarity reversed.

    If I bring in the 10th version and reverse polarity the maximum level on the meter is -39.1dB on Cubase's meter. The original channel on it's own reads -15.7dB on it's own.

    On a blind test between version one and version 10, with all those eq reversals - subjectively I can hear no difference whatsoever. A stereo scope across the stereo output shows a horizontal line as it should when nulled, at at maximum null the difference is in the mid-range.

    What does this prove? There is loss - the evidence is in the lack of absolute null in the first to an impossible null after v10, however, to be sure it was not linked to eq changes each generation I repeated the test adding .05dB on the first generation, then -0.5dB on. the 2nd etc. The results are identical apart from a small eq shift IU can detect with my ears in the eq modified ones. The Null gets poorer as generations increase. This to me is evidence of the waveform being degraded, but the degradation is small, very, very small!

    I can detect either by listening or by the information on the screen that Cubase does things any differently to Sound Forge - It is easier in cubase to accidentally move a track in time, but other than that, I'm pretty content to say that there is multi-generation audio degradation as soon as the waveform is tinkered with. It does not build up quickly as analogue does, but it is detectable by using tricks like nulling, but my ears simply cannot hear it. Others should perhaps try the same thing on their systems?
     
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  13. paulears

    paulears Well-Known Member

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    I'm really PI**ED OFF - I just wasted over an hour doing this and because people weren't too receptive and wanted to check he throws his toys out of the pram in such a childish way.

    I'm quite happy I have proven something to myself - that I should not ever worry about the difference between a few digital copies of copies. As we say here in the UK = Plonker!
     
  14. pcrecord

    pcrecord Quality recording seeker ! Distinguished Member

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    Oh boy, this escaladed quickly !
    Emotions under written words are hard to evaluate. Boswell is one of the most gentlemen like person here on RO and has a TON of knowledge to offer.
    He simply wanted this thread to go on because RO is all about discussion not giving an answer and run.

    Wish you luch anyway !
     

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