is PCM=FLAC ?

Discussion in 'Audio Hardware' started by hans1000, Oct 11, 2011.

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  1. hans1000

    hans1000 New Member Thread Starter

    Dear forum members can you please educate me on FLAC 24b 96 KHz compression as I'm stuck

    to my understanding FLAC is a lossless compression and therefore I should not hear any difference if I listen to my DVDA (PCM) music or the same music but then converted into flac ( both are 24b and 96 KHz)

    But I do hear a difference, not in dynamic range or less freq spectrum that is still great but it seems that the flac files lost their magic or call it color compared to the original PCM. Always difficult to describe things but perhaps you could compare it that when you listen to the DVDA / PCM you see the band performing on stage but in flac it looks like they are playing behind a thin curtain. the music is no longer in the front of the speaker but more hidden in the back of the speaker

    Does this makes any sense ? is it something I imagine. It tried this out with different DVDA and depending on the recording it is more or less noticeable. but it's always there. I hear it very good on the Alice Cooper DVDA recording billion dollar baby

    any thought ?
     
  2. wolfram

    wolfram Slave to the rhythm

    Location:
    Berlin, Germany
    As you said, FLAC is lossless and so you shouldn't hear any differences. How do you play the FLAC files and how the DVD-A? Are both being played through the same DAC? If not, that might be your answer.

    In my understanding and experience there is no difference in quality between PCM and FLAC (identical bits), but some members may have different opinions.

    Welcome to the forum btw.

    :wave:
     
  3. wolfram

    wolfram Slave to the rhythm

    Location:
    Berlin, Germany
    Another question would be how you converted the PCM from your DVD-A to FLAC. Has it maybe been downsampled accidentally?
     
  4. BrewDrinkRepeat

    BrewDrinkRepeat Forum Resident

    Location:
    Merchantville NJ
    If you convert the FLAC file to an uncompressed format (WAV or AIFF), and do a bit-for-bit comparison to the uncompressed version, they will be identical. That by definition is lossless compression.

    I don't hear any difference on my system between Apple Lossless (which I use instead of FLAC) and AIFF, but I know plenty of people do. In these cases it comes down to how their system handles decoding the FLAC files on-the-fly during playback, and since that does involve an additional process that playing uncompressed files doesn't require there is that opportunity to introduce sonic differences.

    Hope that makes sense...
     
  5. bdiament

    bdiament Producer, Engineer, Soundkeeper

    Location:
    New York
    Hi hans1000,

    To me, it makes complete sense. I don't believe you are imagining it; I believe you are hearing it.

    In my experience, so-called "lossless" compression allows one to use an offline process to expand the file and recover the original data. This works with offline processing (i.e. NOT while listening) but in my experience, it doesn't work when expansion takes place during listening. This may be due to increased jitter or it may be due to something else but to my ears, these do not sound the same as raw, uncompressed PCM (e.g. .aif or .wav).

    The sonic symptoms remind me of jitter, which I why I suspect there is more when playing back compressed files. To my ears, bass is looser, mids and highs are rougher, air is lost, dynamics are reduced. The bits may be correct but as someone else once said: "The right bit at the wrong time is the wrong bit."

    Remember it wasn't that long ago we were told CDs represented "perfect sound forever". As most of us know, they turned out to be (in the lucky cases) "decent sound, as long as the disc lasts".
    I think the great Wilma Cozart put it best: "Trust you ears".

    Best regards,
    Barry
    www.soundkeeperrecordings.com
    www.barrydiamentaudio.com
     
  6. utenteanonimo64

    utenteanonimo64 Well-Known Member

    As discussed in about one million threads I always find it hard to understand what is producing this "thin curtain".
    May I ask why your DVD-As do not produce such curtain when in fact they have data stored using a lossless compression called MLP? So FLAC decoding intruduces the curtain but MLP decoding doesn't.
    Could it be that with DVD-As you were not aware that this decoding happens so you don't "hear" any problem, while with FLAC you are aware and therefore you "hear" problems?

    http://en.wikipedia.org/wiki/Meridian_Lossless_Packing

    "MLP is the standard lossless compression method for DVD-Audio content (often advertised with the Advanced Resolution logo) and typically provides about 1.5:1 compression on most music material."
     
  7. bdiament

    bdiament Producer, Engineer, Soundkeeper

    Location:
    New York
  8. direwolf-pgh

    direwolf-pgh Well-Known Member

    yes, your dvd-a playback device has coloured in conversion.
    and/or you may need to diag your playback config for 96/24 FLAC files (you didnt mention what equipment was used)

    :) 2¢ and hello!
     
  9. utenteanonimo64

    utenteanonimo64 Well-Known Member

    Yes but in my experience most DVD-As use MLP also for stereo and I haven't heard any complaint about quality degradation because of this.
    I would like to ask the OP if he hears any quality difference between pure PCM DVD-As and MLP encoded DVD-As or even better if he can tell without looking at the DVD-A box.
     
  10. GreenDrazi

    GreenDrazi Truth is beauty

    Location:
    Atlanta, GA
    The Alice Cooper "Billion Dollar Babies" DVD-A, that you mention as being a very noticeable difference, is MLP encoded (lossless) for both the 2.0 and 5.1 mixes.

    If you’re hearing a difference, then it’s the differences between the DAC and its analog out stages of your DVD-A chain vs. the DAC/analog out chain of the flac playback chain. You can eliminate most of the differences in the two chains by either using the same DAC for both formats or decompressing the Flac file to an uncompressed format, such as wav or aiff, and then compare both formats (flac & wav).

    Also, please note that lossless audio formats convert to bit-perfect PCM data before they are delivered to the DAC.


    It would be helpful if you describe your playback gear for both formats, including the music server/computer player (with settings), the soundcard (if using SPDIF), and the DAC, as the setup of these items may be a significant part of the issue that you are experiencing.
     
  11. utenteanonimo64

    utenteanonimo64 Well-Known Member

    This is exactly what I think.

    :righton:
     
  12. hazard

    hazard Forum Resident

    My audiophile friend tells me that he doesn't like FLAC files. The compression has killed the music. So he stores all his needledrops (24/192) as wav files. So we do a little test. I created 6 test tracks, one wav and one flac for each track. Play them in random order and ask which one he prefers and guess what - flac version was preferred 5 out of 6 times!!!! Does that mean FLAC is actually better?

    No. It means its all in his head. When he knows he's listening to Flac, he doesn't like it. When he's listening to 2 different versions, he's trying to pick out the best one becasue he "knows" that they are different. Fact is, they sound the same, but he couldn't say that because he had already emphatically stated that FLAC kills the sound.
     
  13. SgtMacca

    SgtMacca New Member

    Location:
    Columbia
    Your audiophile friend has no clue about the difference betwen compression of audio signals and compression of digital data.

    FLAC is a form of data compression and has no effect at all in sound quality.
     
  14. mwheelerk

    mwheelerk Believe In Music Record Shop

    Location:
    Gilbert AZ
    My library is all Apple Lossless. I did this initially because I perceived this to be the best sound quality versus file size compromise. Since file size is no longer a concern would I, in your opinion, benefit by converting all my ALAC files to AIFF files so this 'expansion' does not occur during playback/listening?

    Is there any downside for me to do this (other than the time and effort it will take and a suddenly much larger library)?
     
  15. Grant

    Grant A Brady-Boomer Musical Free-Spirit

    Yeah. Another person mentioned it. It all depends on how that FLAC was encoded, meaning that the FLAC encoder may have done some downsampling or dithering to that hi-rez file to cause the sound to change. Or, the decoder you are using may be doing some funny stuff. Other than that, FLAC will preserve the original sound that was encoded.
     
  16. Jimbo1960

    Jimbo1960 Forum Resident

    I usually end up storing my music as .wav since hard drives are so inexpensive. While I cannot hear a difference between flac and .wav I have had my Oppo BDP-95 'choke' on very large flac files...never on .wav.
     
  17. yamfox

    yamfox Forum Resident

    Location:
    USA
    I love Barry Diament's work to death, but this is something I would disagree on. From a technical standpoint, the quality should be exactly the same.
     
  18. Vidiot

    Vidiot Now in 4K HDR!

    Location:
    Hollywood, USA
    I think it would depend on the processor doing the decoding. One way to accurately judge the test would be to use a second computer to capture the analog output of the first. Playback the FLAC and record it to a second computer; playback the PCM and record that to a second computer. Now, take the two files and compare them to each other. I'd be very surprised if they weren't bit-for-bit identical.

    I agree with Barry that there was a time when I think older processors couldn't keep up with accurate decoding in real time. I use to routinely hear "blips" going on every minute or two in playback files, both on Pro Tools and in other programs, on 1990s and early 2000s Macs and PCs. But I think that problem went away about 5 years ago, assuming very fast processors and lots of RAM, and not a lot of background activity.
     
  19. acdc7369

    acdc7369 Forum Resident

    Location:
    Pittsburgh, PA

    This.
     
  20. MikeyH

    MikeyH Stamper King

    Location:
    Berkeley, CA
    This is clearly a subtle effect, and one undoubtedly has to 'learn' to hear it.

    I don't hear a difference, but I'm prepared to think that the decoding work could result in some difference between real-time played flac and wav. Something to think about later. I actually have a quite slow (780MHz) pentium and don't really have a problem with glitches and the like provided I don't do stuff too much. Three downloads, surfing, email and needle drops.. no.
     
  21. EddieVanHalen

    EddieVanHalen Well-Known Member

    I did my own experiment with Flac. Ripped a couple of tracks from the Titanic soundtrack DTS CD and then converted them to Flac. Tried to play them through my Oppo BDP-93 and output the signal by digital coaxial to my A/V receiver. The DTS recompressed to Flac played flawlessly, no glitches, perfect as if it was the original CD, so Flac didn't alter the DTS data stream.
     
  22. onlyconnect

    onlyconnect The prose and the passion

    Location:
    Winchester, UK
    If you have a PC you can install Foobar2000:

    http://www.foobar2000.org/

    which has an ABX plug-in that lets you compare two audio files. You can then install the ABX comparator:

    http://www.foobar2000.org/components/view/foo_abx

    which lets you test whether you can hear the difference between two files. This is a great way to eliminate the possibility that the differences are due to expectation bias - eg. you hear the FLAC and expect it to be missing some magic, so it is - or whether you can actually hear the difference.

    Tim
     
  23. The Hawk

    The Hawk Member

    Location:
    Toronto
    I'll grab me coat...
     
  24. wolfram

    wolfram Slave to the rhythm

    Location:
    Berlin, Germany
    I hope people are aware that the thread starter has never checked back in after starting this thread.

    Last Activity: 10-11-2011 08:01 PM


    But others might find this interesting as well.
     


  25. Weird. I have been following the thread with baited breath. :winkgrin:
     
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