Does FLAC sound the same as a WAV?
There are programs that can compare two files, for example, the original uncompressed audio file and the converted lossless file. These programs check the files bit for bit and can confirm whether or not they are in fact bit-perfect. Still, this isn’t the entire story. At the risk of being called crazy, and even though many people claim that the bit-check programs negate the need for any further investigation, I hereby claim that FLAC files when played back in real-time don’t necessarily sound the same as their original WAV files.
It annoys me sometimes, the ease with which people can generalize and trivialize complicated audio matters, based upon a simple equation. Fundamentally this is along the lines of technicians who claim that measurements tell the whole truth and nothing but the truth. And that you can’t hear what you can’t measure. While this is true in principle, I would leave space for the possibility that there are factors of influence that we either don’t (yet) recognize or are not measuring.
In matters Lossless Audio, saying that two bit-identical files sound the same is more or less akin to saying that a CD-R and the original CD sound the same, just because they are bit-accurate copies. Many people have found out by now that this is simply not the case. Even bit-perfect CD copies can sound quite different from the original. Why? I’m not entirely sure. But it could well be the ever-popular jitter or interdependence between the rougher pit shape and the optical unit that reads them and the resultant error-correction, or, well, I just don’t know exactly. I do know, however, that I can trust my ears. And they are telling me that there are clear differences between CD’s and copies. But of course, this comparison isn’t quite right in this case because both cd and CD-R are being played by the same player, with the same decoding circuits.
Back to the lossless story then. If bit-identical CDs can sound different, why not a bit-identical lossless file and its original?
If we can accept the above situation for CD’s and CDr’s, could we perhaps also accept that the situation may be the same for lossless formats? Just because the bits are the same after the calculations, this doesn’t mean that the bits are exactly timed alike. Or that a given codec decodes them completely transparently. And then there is the issue that different codecs can sound also different and therefore any given playback application could have better support for one format over another. It could well be that the bits are perfectly alike just as long as you make an off-line comparison but not when it has to be done real-time, on the fly, when you playback the audio file. I can also imagine that one codec doesn’t need to sound like the other, just like iTunes doesn’t sound the same as Winamp. I know this for a fact because I have tested this extensively.
I came across a piece of text on the internet that confirms my beliefs, I’ll reprint it here: Keith Johnson, the inventor of HDCD, claims that only WAV files guarantee perfect sound reproduction which can’t be achieved with any compression, even lossless compression. He says that any file processing even in the digital domain alters it and that executing FLAC decoding affects the sound.
Just to ease my mind and, perhaps, also the mind of some readers, I put the lossless statement to the test. For this, I took some FLAC files and converted them into AIFF (identical in quality to WAV) using the well-respected Amarra software for the Mac. I also ripped some tracks using iTunes both in WAV and Apple Lossless. Then I compared all these files using the USB-attached HiFace EVO that connects to the s/pdif input on the Levinson no.360S DAC of my reference system. Playback of the files was done in iTunes natively for the Apple Lossless versus AIFF comparison and in iTunes with Amarra for the FLAC versus AIFF converted FLAC files comparison. Then I repeated the comparisons using VOX, a nice little application that plays almost all formats.
iTunes ripped tracks – AIFF versus Apple Lossless
This comparison surprised me. Turns out that there is not a whole lot of difference in sound between these two formats. At first listen I couldn’t tell the difference. Then, after a couple of switches back and forth I slowly started hearing some things. Suspicion arose that the Apple Lossless file was somehow rhythmically a little slower. Closer listening revealed that indeed WAV sounds a little snappier, with sharper transients. Apple Lossless has exactly the same tonal qualities and frequency curve etc, but it is in the speed and dynamics department that it shows small differences. The timing is a little off and transients are a little bit softer. The differences re slight though and I can imagine that many people would struggle to hear them. So, unless you’re an anally critical audiophile, like me, you’re probably fine using Apple Lossless as a basis for your audio files. The bonus is that Apple Lossless has much better support for tagging. In WAV this is virtually absent.
Original FLAC files versus AIFF-converted FLAC files (using Amarra)
Again I was surprised by the quality of the conversion. Considering what I had read in the forums I expected much worse. There is a difference though. But the difference is different from the one between Apple Lossless and AIFF. While the differences between Apple Lossless versus AIFF were in the temporal and dynamic department, for FLAC and AIFF-converted FLAC files it was more to do with fullness, color and soundstage size. The converted files clearly sounded flatter and less full, somewhat leaner in balance. Not bad at all, but bad enough for me to decide not to convert the FLAC files I have but instead aim for native playback. Otherwise, you would be stacking problem atop of problem: Lossless is already compromised and by converting the file you would remove even more quality.
Conclusion
No matter what application is used for playback, be it VOX, iTunes, iTunes controlled by Amarra or Amarra natively, the differences can be heard. They are not incredibly large and I should note that FLAC definitely sounds very good. The discerning audiophile will want to use either native FLAC playback (without on the fly conversion) or use WAV/AIFF.
Update June 2011
Now that I have the PS Audio PWD in place, I still hear the same differences between WAV and FLAC, but because the PWD is so much better than the best computer solution I had found thus far, being much more dynamic and musical, FLAC can no longer be quantified as sounding any less than WAV. It is just different. Using PS Audio’s eLyric as a music server, feeding the PWD as a media renderer, FLAC sounds a little gentler and lighter and has less bottom power (bass slam) than WAV. What’s more: in this particular case, FLAC even helps ameliorate the PWD’s slight dryness and actually sounds more pleasant than WAV. More on this can be found in the PWD review.
Update December 2011
I know that there are many skeptics when it comes to hearing differences between FLAC and WAV. But in the meantime, I read more and more posts from other people hearing the same thing. Recently I even found a post by J Gordon Ranking, a person with an enormous technical background and apparently decidedly non-Hocus Pocus believer. He mentioned that he has been hearing differences between FLAC and WAV for ages when it is combined with streaming over USB. He even went on explaining the possible reasons behind this but had to admit that to date, he just wasn’t sure. Well, if Gordon doesn’t have the answer, perhaps no one really knows. But hey, explanations are nice but do you really need them, when the differences are audible?
What about AIFF vs WAV?
I use dbpoweramp and i would like to hear you about sound of AIFF vs WAV?
I haven’t done a one on one comparison between these formats yet, but WAV is just a Windows variant of AIFF. As I understand it only the header differs and the file itself is the same, so theoretically there should not be a difference. Naturally there are other variables that could make for audible differences after all. If I do make a comparison using dB poweramp for ripping and jRiver Media Center for playback and hear a difference, I’ll post an update.
Although some people will probably fry me for this as WAV and AIFF are actually the same format but with different headers, I have heard differences between AIFF and WAV at some stage, but I conducted that test a long time ago and I forget the precise circumstances. At the time I wanted to tag my WAVs, but this was only possible with AIFFs, so I converted the WAVs to AIFFs to allow this. In the process I noticed that the sound became a little tighter and less free-flowing after conversion. But this might as well have been the result from the conversion process itself. The difference was not very large though and probably not worth fretting about.
https://lacocina.nl/bitperfect-audio
Ronald claims flac is bit perfect!!
Ronald van Engelen wrote:
“While flac is a bit perfect encoder/decoder for digital audio, the extra decompression that takes place when playing back the audio within a flac file, adds to the total load of the playback computer, which is something we’re trying to avoid. Therefore flac should not be considered suitable for usage in a bit perfect audio playback chain, although it is a great tool for efficient and accurate archiving and transport.”
Interesting article, thanks Amir.
“Ronald claims flac is bit perfect!!”
FLAC is a lossless format by design. No reason to be surprised if e.g. “Ronald” says so.
If you don’t believe it is, do a conversion:
WAV1 > FLAC > WAV2
Do a binary comparison of the audio part of WAV1 vs WAV2 and you will detect zero differences.
Hi Vincent, I’m not sure that I get your point, or if you are responding to me or the last comment. In any event I know that FLAC is indeed lossless and I’m sure that if you converted WAV to FLAC and back the result should be identical to the same WAV that I started with. The point of my article is that in many cases (the difference is not always very evident and sometimes even inaudible) in spite of the above there is a difference in sound if you compare WAV and FLAC when played back natively, so converting in real time.
PS I like your site and have spent lots of time on it!
Hi Christiaan
Basically on the comment.
But your 2011 Update “hearing differences between lossy FLAC and WAV “ raises an eyebrow too.
“lossy” FLAC???
Ah, well that’s simply wrong. I’ll update it right away.
[…] Lossless Audio (FLAC) | HFA – The Independent Source for Audio. – Dec 24, 2010. Lossless computer audio file formats such as FLAC are technically lossless indeed. For this, I took some FLAC files and converted them into AIFF (identical in quality to. iTunes ripped tracks – AIFF versus Apple Lossless. I use dbpoweramp and i would like to hear you about sound of AIFF vs WAV? […]