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Mastering engineer Truth or conning?

Discussion in 'Mastering' started by Gazukmale, Apr 6, 2017.

  • AT5047

    The New AT5047 Premier Studio Microphone Purity Transformed

  1. Boswell

    Boswell Moderator Distinguished Member

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    The last time I talked to an ME specifically about having separate MP3 and CD masters, he said he set the compression and limiting differently for the two formats. His argument was along the lines that, as CD players are increasingly less common in new cars, you need a version with less overall dynamic range for playing in vehicles. Given that he was dealing with my folk/jazz recordings and not rock or other styles that have inherently self-limited DR, I'm not sure I buy that argument.
     
  2. audiokid

    audiokid Chris Staff

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    I'm not trying to be an ass here but I have a desire to learn all I can by questions over and over until I get it right. I really want to get to the bottom of what you are saying here, that I simply do not believe (YET). :)

    What I am hearing said over and over is no different to someone saying;
    "The guitars were in tune or in phase, but now they are out of tune or out of phase because its an MP3 now."

    Then my inner voice keeps saying this about lower bit rates, ...

    Is this distortion actually revealing my lack of attention to detail? Is the MP3 code having trouble rendering the (L-C-R) adjustments and the result are the sound of a bit pile up of audio that ends up peaking into swirly distortion?

    So far I am convinced this isn't the fault of the mp3. It is the indication of recording, mixing and mastering improvement. The MP3 is simply making it all more obvious.

    Kind of like reducing soup until you taste all the salt in it.
     
  3. bouldersound

    bouldersound Real guitars are for old people. Well-Known Member

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    I don't think the ME the OP was dealing with was talking about dynamics. He was saying that if the file is going to undergo psycho-acoustic (lossy) compression that the song's peak level would rise and that there had to be some accommodation for it. It seems to me it should just be built into the compression algorithm.
     
  4. bouldersound

    bouldersound Real guitars are for old people. Well-Known Member

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    I totally get that and appreciate your skepticism. Try it yourself. Render a wav file with 0dB peaks, compress it to mp3 and reimport it. I didn't believe it until I did the test myself.
     
  5. audiokid

    audiokid Chris Staff

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    Does that happen for you with a mono file?
     
  6. pcrecord

    pcrecord Quality recording seeker ! Distinguished Member

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    iZotope Ozone has a codec preview ment to help listening to what will happen to our files once converted..
    I honestly didn't care about it until now.. but it's gonna be on my radar on my next projects..

    https://www.izotope.com/en/community/blog/tips-tutorials/2015/11/using-codec-preview-in-ozone-7-advanced
     
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  7. bouldersound

    bouldersound Real guitars are for old people. Well-Known Member

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    Yes. I started with a stereo file with -0.3dBFS peaks, converted it to mono using only the left channel (no summing), confirmed it still had -0.3dBFS peaks, converted it to a mono mp3, reimported it. I can see multiple-sample sequences of 0dBFS.

    In the image below the wav is on top, the mp3 is below. It's the same point in the song, though the time selection shows it slightly different due to mp3 compression adding a bit of delay at the start of the file. The wav is peaking at -0.3dBFS while the mp3 is peaking at 0dBFS. The wav is already somewhat flat-topped due to client demand for stupid loud, but I did leave that -0.3dBFS of headroom for the benefit of converters that lack the headroom to deal with ISP.

    mp3 clipping_cropped.JPG
     
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  8. audiokid

    audiokid Chris Staff

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    Sequoia does this with flying colours. The next version will be improving upon it. iZotope and Sequoia are where I would be looking as well. And Fabfilter ProL is a staple for me. Use that and you never have a problem you can't hear.

    Quite frankly, I never have this problem, never experience it. I simply do not relate to any of this but I understand it and believe its being noticed.
     
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  9. audiokid

    audiokid Chris Staff

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    exactly my point! But... I like where this is going now. I'm open to being schooled on this one.

    Please try this with a mono wave file now. Not stereo. (mono to mono)
     
  10. bouldersound

    bouldersound Real guitars are for old people. Well-Known Member

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    I just did that. I discarded the right-channel information and converted the wav format to mono. It is in fact a mono wav file with -0.3dBFS peaks. You can see for yourself in the pic that there are two mono audio files, one wav and one mp3. That it came from a stereo file is irrelevant.

    What you're suggesting is that it has something to do with altering of the stereo image by the compression algorithm. That is not the case here. I did not give the mp3 encoder any stereo image to mess with, just one channel of audio in wav format that it converted to one channel of audio in mp3 format.
     
  11. audiokid

    audiokid Chris Staff

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    Thanks you for doing this.
    I am now wondering if ALL DAW's fall apart here.
    Boulder, you are on Vegas, correct?

    When I can actually get my new studio back, I am going to pursue this with Sequoia and will repost back with my results.

    In the mean time, I think this deserves a bunch of DAW's being tested.
     
  12. dvdhawk

    dvdhawk Well-Known Member

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    Can you clear that sentence up?
    Do you hear distortion or not, if so, what are you listening through for playback?
    How reputable was the ME?

    If there's distortion in the CD meant as the replication master that seems like a concern regardless of artifacts the mp3 conversion may have.
     
  13. bouldersound

    bouldersound Real guitars are for old people. Well-Known Member

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    I'm not using a DAW, I'm using Sound Forge 6 to take the right channel information out, change the wav format from stereo to mono and examine the files. It's ancient but that is irrelevant. It's not a matter of metering. I used the Statistics function to confirm the change in peak level from -0.3dBFS to 0dBFS that can be seen in the waveform display.
     
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  14. bouldersound

    bouldersound Real guitars are for old people. Well-Known Member

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    I just put the same two files into Audacity, and used Audacity to make a mono version of the original stereo wav (split track, delete right channel), and got the same results.
     
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  15. audiokid

    audiokid Chris Staff

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    Are we defining and confirming this is what happens to all MP3 files no matter what DAW platform?
    All DAW's use the same process to arrive at an MP3? I am aware their is a patent on MP3 but was not aware of how we arrive at it all the same way.

    Summary: The least expensive MP3 process always does the math the same.

    My next question:
    Hypothetically: If we were to import a wave session done at example: Sterling Sound, only to use Sound Forge 6 to turn it into an MP3, it would end up with a change in peak level from -0.3dBFS to 0dBFS .. thus... same sounding MP3?
     
  16. bouldersound

    bouldersound Real guitars are for old people. Well-Known Member

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    I didn't use Sound Forge to make the mp3. Generally speaking I don't make mp3 files myself, I upload wav files and let the site (e.g. to Soundcloud) make the conversion. So I had to search around to find something to convert the file. All I could find was Cool Edit that's been on this machine for at least a decade. Sound Forge is not a DAW, it's an editor, as is Audacity. Cool Edit is also an editor though it has some DAW-like capabilities.

    It would be a good thing for others to repeat this with different editors and different mp3 encoders. I'm going to install LAME so Audacity can be used to convert wav to mp3 and try this again without using Sound Forge or Cool Edit at all. My money says I get the same result regardless of the editor or encoder.
     
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  17. kmetal

    kmetal Kyle P. Gushue Distinguished Member

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    From what I understand MP3 conversion in general, reguardless of brand, can cause/reveal inter sample peaks/distortions, and does come out slightly hotter than the .wav. I recently read an article somewhere, or maybe on the tube, where the engineer was saying they leave more headroom on a separate mix destined for MP3 conversion. Like -.5 or -1dbfs or something.

    Whether or not all conversion algorithms are created equally or not I'm skeptical, but from what i understand they all do those things to some extent.

    I'm excited to compare Samplitude, sequoia, izotope, and sonnox codecs to hear it there's any audible differences or not. Codec shootout anyone?
     
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  18. audiokid

    audiokid Chris Staff

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    Whats interesting, when I am exporting a mix to MP3, or online for that matter> letting the online software do their compression, I never hear my online version distort. In Sequoia its so simple. I set my limiter to -01 (a bit below 0) and it sounds like it should online.

    So because I don't hear my mix distort, I have never looked to see this happens. I'm surprised actually. Ill do some shootouts once I get new converters.
     
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  19. kmetal

    kmetal Kyle P. Gushue Distinguished Member

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    I also wonder if the source sample rate or bit depth has anything to do with it.? Like if you convert to MP3 from say 24/96 or from 16/44.1. I wonder if there's any general rule of thumb on that?
     
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  20. audiokid

    audiokid Chris Staff

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    Thats interesting. I mixdown/ finalize to a second DAW as you know, which is always 44.1/24 . Boulder, are you doing these comparisons at 44.1 ""?
    I think he said he was, Kyle.
     
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  • AT5047

    The New AT5047 Premier Studio Microphone Purity Transformed

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