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FLAC vs. 320 Mp3

Discussion in 'Sound Science' started by icedup, Sep 7, 2011.
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  1. anetode
    Quote:
    Comparisons between image and audio compression are misleading and show a naive understanding of both approaches. Artifacts in JPG compression are caused by chroma subsampling and block-splitting, with the results processed by a discrete cosine transform and then quantized to allow for a more efficient lossless entropy coding. All of these approximations become obvious even in low compression ratios as you can test by simply zooming in to a JPEG which features curved gradients and high-contrast outlines. A JPEG is static, whereas an mp3 is not. The first step in mp3 compression involves breaking the uncompressed file down to samples and these samples to frequency bands which are then analyzed by a fast fourier transform. The FFT data is then run through a psychoacoustic model (think auditory masking) which further sorts the results into time slices, "windows" based on whether there's a steady noise or a transient. One so sorted the information is then fed through a modified discrete cosine transform which has the remarkable property of time-domain aliasing cancellation (i.e. removing artifacts because of a signal which changes over time, unlike that of a static image).
     
    The impetus behind lossy compression is how best to take advantage of the limitations of different human sensory apparatus. Your eye depends on detecting changes in chrominance and luminance but your auditory system depends on sensing rates of change of air pressure and minute differences in interaural-cross correlation. Whereas one can spend hours looking at a painting, photograph, jpeg or other static facsimile of visual stimuli with a magnifying glass and under different lighting conditions, you are not accorded the same luxury with the dynamic medium of audio. Actually it's even worse, since you are also subject to listening in an artificial and necessarily limited sound field where reflections and transducer limitations conspire to further distort the original signal (not that you'd ever perceive the "whole" signal because of auditory masking anyway).
     
    To address your final point, there has been quite a bit of research over the past forty years in developing a consistent vocabulary used to describe audio quality and even training programs for listeners to acquaint them with judging specific aspects of sound.
     
    The reason I'm calling you out in this spiel is because I want to stress that nothing is ever as simple as it seems and proper comparisons of signal processing methods require not only an appreciation and keen senses but also an understanding of the underlying physiology and mathematics.
     
  2. bigshot
    There is a definite advantage to stating things clearly and simply.
     
  3. Dillan

    I wish I knew more about photography. Maybe Forshure was a little off comparing the two, still an interesting topic either way.
     
  4. chewy4
    Quote:
    I think naming it anything else would give much worse impressions.
     
    In regards to integrity it's most certainly lossy, quite a bit really. To name it something other than that would just make things confusing and cause even more mixups between this special kind of compression and other forms of compression that preserve data integrity.
     
  5. anetode
    Quote:
    The response was a mistake on my part. I read over the last few pages of the thread and lumped Forshure's comment with a line of inane arguments from someone else and so misinterpreted the intent of his post. Sorry, for sure.
     
    In order to salvage that errant post I might as well dig deeper into what he actually said with regards to RAW. There I would analogize the process to the initial 24/96 ADC during recording which allows for the mixing and mastering at a higher resolution prior to downsampling and dynamic compression, followed by conversion to an industry standard format. If you were a music producer then given an mp3 source would surely count as an insult and possibly limit the fidelity of your final product, but from an end-user standpoint [proper] compression is not such a bad thing. FWIW, we've advanced from the days of 128kbps DRM crap sold by iTunes.
     
  6. bigshot
    That's a bingo.
     
  7. Dillan
    We have advanced that's for sure. Everything just comes down to the individual, which most people in the world will gladly take their low quality 128 mp3 file and be happy. Some people feel a proper formatted, compressed lossy file is just fine and others are comfortable with a fool proof flac collection. There isn't really an end to the argument between the audio itself, only reason behind choosing which and why.
     
  8. bigshot
    Well, an artifact filled 128 file isn't the same as an aurally transparent high bitrate MP4 or lossless track. We're talking here about two types of files that are identical to human ears, the only difference being the file size. A low rez MP3 is a different animal altogether.
     
  9. Dillan
    Well whether every single lossless file is the exact same sound wise to every single lossy file, even the high quality lossy files.. Is what I am not willing to admit. Even though I am willing to say I personally couldn't and still can't tell a difference for the most part, I just can not sit here and without all doubt be 100% confident in the fact that there isn't a possibility.
     
  10. bigshot
    I wasn't saying that every single lossy file sounds the same as lossless. Obviously low bitrate lossy files don't, just high bitrate ones. The fact that high bitrate MP4 is audibly transparent to lossless has been proven in controlled testing. I totally understand you feeling uncomfortable about data being missing. That's perfectly fine. But again, that has nothing to do with actual perceived sound quality. That is something you would just worry about because of your particular personality.
     
  11. Dillan
    I mean yea. I still stand by my statements. I feel that most low quality lossy files are easily and audibly different than lossless, and I feel that there is at least the possibility that some sort of difference can be heard of even the highest quality lossy versus its lossless counterpart. Like I said, especially with thousands upon thousands of albums. No matter how insignificant that difference may be. I at least can say that there is a possibility, no matter how small, how large. If someone was to disagree with me, then that's totally ok. But I feel safer with FLAC and I think its a good default format to stick with in my situation. Especially because some remastered, undiscovered albums like to find there way in 24/96 and above on the internet. Those can be great not because there are just lossless but because they are different (better) than the original, or can be something never put out on cd or vinyl in the first place. That's just the way it is, and i will always feel strongly about that. I like a solid fool proof collection that creates a barrier around it, where no one could possibly say that lossy would sound better, only the same at best. I don't know how else I can say it.
     
  12. Brooko Contributor
    Quote:
     
    Rem1x - I hear where you are coming from.  I'm really curious though ..... have you actually tried the controlled abx with Foobar (I linked the how-to earlier in this thread - http://www.head-fi.org/t/655879/setting-up-an-abx-test-simple-guide-to-ripping-tagging-transcoding).
     
    If you try the abx - do it with as many tracks / genres / different albums as you can.  All it will cost you is time.  When I did mine - I abx'd ~ 15-20 different tracks all from different albums - ranging classical and jazz right through to rock and alternative.
     
    I totally understand your comments so far - but until you actually perform the abx, then saying 'strongly' that you feel flac is better isn't really fair.  You've never comprehensively compared the two.
     
    Please note with all of this - I'm not on a crusade here - I just think it's better to know both sides of the story :)
     
    FTR - I still also rip to FLAC - and listen to my own collection as FLAC files on the PC.  I do this simply for archival purposes - and the fact that if they ever come up with a better lossy/compressed format, I won't have to rerip any CDs.  But for my portables - I only ever use lossy (aac vbr ~200), and I'm quite comfortable about using that at home as well - to my ears it's audibly transparent.
     
    I'm just really interested to hear your impressions AFTER performing a multitude of abx tests - would your initial feelings change?  If you're not inclined to do the abx - no problem.  It's been refreshing to hear your comments.  And I do understand about the OCD tendencies - can totally relate :)
     
  13. Dillan
    I guess it wouldn't hurt anything to do those tests. Like I said I have done a few blind tests, but I feel like my echoic memory is so bad it makes things really difficult. I think I'll take you up on that and set it up tonight or tomorrow and post my thoughts afterward.
     
  14. chewy4
    The nice thing about Foobar's ABX comparator is that you can switch between the files really quickly and even at the same part of the song. Still requires some memory work if you're passing over the same part to try and identify changes, but it does a great job at showing whether or not there is an overall change in the sound(which there shouldn't be for 128kbps and above).
     
    Now if only they could get rid of that click and somehow make the transition seamless.
     
  15. waynes world
    Quote:
     
    I recently got sold the kool aid into believing that I can not tell the difference between flac and 320kbps LAME encoded MP3 files - those were my findings previously anyway when doing my own crude ab comparisons in foobar - and I doubt the abx comparator will change that opinion. But, I'm pretty sure I can tell the difference between 320kbps and 128kbps, so I'll probably get the comparator going to at least try out that comparison.
     
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