Digital audio file formats demystified
That’s a wrap.
Digital audio can be recorded and subsequently encoded in a variety of formats and qualities. When you're downloading a file from a download site or streaming from an online subscription service it can be hard to know which file format to choose from the bewildering array on offer.
99.999% of all digital audio is originally recorded in one of two formats: PCM or DSD. Those original files are then “wrapped” for delivery in a few different ways.
For PCM, the most common “wrapper” you will see for an uncompressed digital audio file is WAV (or “wave”) or AIFF. When downloading the files, or when viewing them on your computer or streamer, you will often be provided with information about the sample rate (expressed in kilohertz, e.g. 48kHz) and bitrate (expressed in bits, e.g. 24bit).
Without getting too technical and at the risk of over-simplifying things, when implemented well, anything at or above 16bit/44.1kHz can be considered high enough quality for playback on a good quality, well resolving hi-fi. A CD, for example, contains 16bit/44.1kHz PCM files.
For DSD, the most common “wrapper” is DSF or DFF—both essentially identical except the former can embed metadata about the file (DSF is generally preferred for that reason). Again you will often be provided with information about the sample rate of the file, such as DSD64 or 64fs. The “fs” stands for sampling frequency and the “64” is as compared to the standard sampling rate for CD (44.1kHz). So if you see DSD128 or 128fs it means the sampling rate is 128 x 44.1kHz, i.e. 5,644.8kHz or 5.6448MHz (megahertz). DSD64 was the original spec for DSD as delivered on SA-CD and so you will often see it described as “single rate”, with DSD128 described as “double rate”, and DSD256 as “quad rate”.
At this point an innocent bystander would be forgiven for thinking that DSD at 64-times the sampling rate of PCM at 44.1Khz (i.e. CD sample rate) must by default be vastly superior to PCM. In reality, they are quite incomparable. PCM and DSD encode digital audio differently (DSD is 1-bit, for example) and both are highly capable formats in the correct hands (and perhaps even indistinguishable from each other in terms of sonics).
Once again I’ll risk oversimplifying things and state that, well implemented, DSD64 can be considered high enough quality for playback on a good quality, well resolving hi-fi, and is practically indistinguishable from PCM at 44.1kHz.
Lossy vs. lossless
So far we have been talking about uncompressed formats. It is also possible to compress (make smaller) digital audio files. We can do this in a “lossy” fashion or a “lossless” fashion.
Lossy would be formats like mp3, where the file size is smaller, but the trade-off is a compromise in sound quality. MP3 quality is expressed in kilobits per second (kbps). The lower this “bitrate” the more compressed and compromised the sound quality. In simple terms, a 128kbps MP3 will sound worse that a 320kbps MP3. (By the way, uncompressed files can also be expressed in kbps. A CD, for example, plays back at 1411kbps.)
MQA is the codec everyone is talking about at the moment. It is a lossy format, but less of a compromise in terms of sound quality than MP3. You can read my thoughts on MQA in a previous article.
Lossless would be formats like FLAC. Most of you will be familiar with the ubiquitous “.zip” and “.rar” files on computers; FLAC is just like that except specially formulated for audio. It compresses your audio file to make is smaller, but when you uncompress it, the original data remains completely intact; indistinguishable from the original uncompressed file. Other common lossless compressed formats are ALAC and OGG. Like WAV and AIFF, FLAC quality is expressed in bits and kilohertz, e.g. 24bit/96kHz.
Cut to the chase: which is best?
For me, if I had to chose one format: PCM at 20bit or higher. If the mastering engineer was good and knew how to downsample well (or if the original recording was at 44.1kHz), I can settle with 44.1kHz. Otherwise 88.2kHz or higher. Whether the file is wrapped/encoded as an AIFF, WAV or FLAC file, I don’t mind. Generally I prefer FLAC because it takes up less disk space.
And finally, my hot tip: please don't waste your money spending more on crazy hi-res 24bit/192kHz recordings. If you have the option of 96kHz and 192kHz, just get the 96kHz version. I guarantee you won't hear a difference unless the mastering engineer is useless (in which case the recording isn't worth hi-res playback anyway).TAGGED: audiophilia, recordingMODIFIED: 6th Jul 2021, 23:15
MQA: the lossy codec no end-user asked for or needs
MQA: it’s 1999 all over again…
I’m not going to work up to a punchline with this rambling essay. I’ll lay my cards on the table right here in the opening paragraph and reveal that I’m sceptical about MQA, and you should be too.
If you’re wondering what MQA is then you are one of the lucky few who have avoided the publicity. MQA is an audio codec—something like PCM, DSD or MP3—invented by Meridian and now owned and licensed under the company MQA Ltd.
MQA is just DSD all over again. Remember a few years ago when SACD/DSD was the answer to our prayers? Remember how this new wonder-format solved all the “problems” with traditional PCM. Remember how DSD marketing bleated on about the shortcomings of traditional PCM, time-smearing, steep low pass filters etc.?
But also remember how our world turned upside down when it came to pass that DSD64 wasn’t good enough. Then DSD128 wasn’t good enough. Now we have DSD256. And DSD512. And DSD-wide, and, and, and… does it ever end. Please, let’s not go through this whole process again. Let’s stop playing this empty number game. I feel like it’s 1999 all over again with MQA. I beg you, boycott this new format before it’s too late.
I’m not suggesting a good recording can’t be made in MQA. What I’m stating is this: excellent recordings can be made and relayed in any number of existing digital formats—DSD or PCM, for example. While my preference is for the latter, there is very little to distinguish between these digital formats and, in ideal conditions, either will play back music which is neither “digital sounding”, nor lacking in fidelity. Comparing MQA to PCM/DSD is comparing apples to apples, especially if we take physical media (CD-A/SACD) out of the equation. This is not comparable to the vinyl vs CD debate. This is not even analogue vs. digital.
Make no mistake about it: MQA is digital. It uses ADCs and DACs. However, rather disingenuously, MQA Ltd is being very ingenious in their marketing and avoid all mention of the word “digital” (unless it is to specifically disparage other digital formats). They don’t ever talk about MQA in digital terms. They are trying to create a “them-and-us” attitude. Ostensibly they are saying, “digital is bad.” I say, “pot calling the kettle black.”
This new kid on the block—MQA—let’s get real… it’s just another digital algorithm. I’m certain excellent recordings can be made in MQA format, but that’s not the point. For reasons which will become clear, MQA Ltd is set on besmirching the reputation of all other digital formats, and I’m not okay with that.
As with all great smear campaigns, MQA Ltd is going to great lengths to expose those dark secrets held by the other candidates. From the MQA site:
- “There’s a problem with digital—it’s called blurring”
- “[MQA] will sound better than CD, the music will be unfolded, reproducing every element that’s in the original recording”
- “Standard digital recording and playback (regardless of sample rate/resolution) smears the timing information and thus distorts the musical input.”
- “When a sound is processed back and forth through a digital converter the time resolution is impaired – causing ‘ringing’ before and after the event.”
Time-smearing this. Neuroscience that. They are trying to give us jitter-fear. Couple that with the pedalling of those same old buzz phrases we’ve been assaulted with time and time again, describing MQA thusly…
- “studio quality”
- “master quality”
- “reproduces the sound of the studio master”
- “step into the magic of the original performance”
- “every tiny drop of emotion is authentically reproduced”
- “a more natural and authentic sound”
- “the result is truly magical”
… it’s so predictable as to become an embarrassment. We’re told, “you can be sure you’re hearing exactly what the artist approved in the studio.” This is all marketing puff. Let me redress the balance.
Reality check 1: no one will ever hear what the mastering engineer heard in the mastering studio, let alone what the musicians heard in the recording studio. That would involve being there, at that time, in that particular studio with that particular setup. It’s simply ridiculous to posit that you can sit there in your living room listening to your MQA enabled device and miraculously hear exactly what the mastering engineer heard.
Reality check 2: Until such a time as music injects directly into our brain, we listen to music through loudspeakers. Even the world’s finest loudspeaker through the world’s most advanced amplification lags way behind high-end DACs in terms of neutrality, time-domain, and phase accuracy. The bottleneck is in the speakers, not the source.
Reality check 3: The hype that MQA is some sort of revolutionary format and that we’ve heard nothing like it before is far from reality. The differences are subtle and, in all instances, could be attributed to the different hardware used in rendering or playback.
But, but… isn’t PCM plagued by pre and post ringing? Answer: if you hear that, then it is the sound engineer or AD/DA designer’s fault, not the fault of current digital encoding/decoding.
All this MQA marketing hype and I haven’t heard of one reputable, objective test proving human beings can hear any significant improvement (note: improvement, not difference) between this new format and any other hi-res digital format. I’m patiently waiting to read about a single, unbiased, scientific test where someone accurately and consistently identifies MQA as better than PCM. Consumers deserve more than words; we deserve facts.
And lest we forget: MQA is a lossy compression format. While it compresses in a pretty innovative way, lossy is lossy; let’s agree to call a spade a spade. Even if we go with the marketing spin and accept that MQA offers hi-res quality in smaller file sizes; well, umm… isn’t that what we already have with FLAC? On top of this, FLAC is genuinely lossless. Yes, we already have a lossless, open-source format supported by a vast number of devices.
While you may think I’m anti MQA, that’s not necessarily the case. Or if I am, it’s not for the reasons you might think. I’m sure it’s a competent technology, but no more or less so than existing digital encoders. That’s the point. We don’t need MQA. No really. It’s completely redundant.
Q. Why do we need MQA?
A. We don’t.
If you’ve made it through my lengthy preamble, the natural thing to ask yourself is why are Meridian and MQA Ltd making such a big deal about MQA? Why are they spending such a considerable amount on marketing? What’s in it for MQA Ltd? I’m glad you asked.
A very worrying (sinister?) aspect of MQA is that it is a proprietary format. Creators must pay a license fee to encode in MQA format, and likewise, people making the playback hardware must pay a license fee to implement MQA in their DAC. Similarly, developers wishing to use the format in their streaming platform (e.g. Tidal) must pay (per stream?). It doesn’t take Hercule Poirot’s shrewd investigative skills to realise that MQA stands to make quite a substantial fortune from their new format, should it gain traction.
If this is proprietary technology, and if the existing formats are good enough and free to use, one might be asking why two of the majors, Warner Music Group and Universal Music, recently signed big deals with MQA Ltd. The answer is straightforward: the “big three” record labels (Universal, Sony and Warner) love new formats. Just when the execs are starting to panic that they’ve milked their cash-cows dry, they can re-release their entire catalogue in a new format. The dumbfounded consumer will buy it all over again, desperate to part with their cash on yet another reissue of Dark Side of the Moon or Hotel California or Gaucho. And because it’s a new format, the labels can charge even more money. The MQA marketing department has ingeniously planted this idea that MQA can resurrect old masters and correct problems with converters used during the mastering. Yes, that’s right: digital remastering of digital masters. It’s an outrageously patronising solution to a problem nobody ever noticed (or worse, doesn’t even exist).
However, kudos to MQA: it is ingenious marketing, bringing all us insecure audiophiles out in a big rash of upgradeitis. We lowly hi-fi enthusiasts start to wonder, “maybe the original AD converter used by Greg Calbi at the mastering session wasn’t good enough and maybe if I sprinkle my Graceland disk with this new MQA fairydust Paul Simon will magically materialise right in front of my very eyes.”
(Related aside: when talking about original masters, it is very telling that MQA’s marketing team have chosen to use the word “reproduce” as opposed to “replicate”. Given that MQA’s success depends on large record label endorsements, they wouldn’t openly suggest that MQA is better than the original master. The last thing record labels want to endorse is the idea a mass-produced product could flawlessly replicate the original master; they would much rather keep on pumping out those remasters in new formats, remember?)
The sinister news doesn’t end there, though. Aside from being merely a proprietary encoding technology, MQA Ltd goes one step further. Part of the license agreement is that an MQA signal can be decoded and “authenticated” only on commercially licensed equipment. In other words, the unpacked data must be fed directly to an on-board MQA-compatible DAC and output in analogue form. (If that sounds like a familiar paradigm, it’s because it’s SACD all over again.) It doesn’t take Lieutenant Columbo’s level of dogged curiosity to realise this amounts to Digital Rights Management by the back door.
One step forward, three steps back.
MQA is not a step forward. It’s a proprietary, lossy digital format that rewards corporations and conglomerates, not artists or end-users. Digital, be it PCM or DSD, has been good enough for years and years now. PCM, in particular, is a mature and wonderful format whose shortcomings we have all but completely eliminated. I’ll go further and say that, in the right hands, the humble Redbook CD (44.1KHz/16bit) is a highly capable format. This is not empty conjecture, but real-world experience recording and listening to a massive variety of music through some of the world’s finest equipment. Today’s equipment outputs a very consistent PCM stream—be it from CD or computer playback—and DACs reclock with such grace and accuracy that jitter (or “digititis”), while a very real threat, can be and generally is entirely eliminated.
With an already bewildering array of digital formats, encoders and delivery methods, little wonder people are craving the simplicity of vinyl. All turntables can play back all vinyl, whether purchased today or 50 years ago. In the digital realm, buy a track or album today and you might find it superseded by a new one at a higher rate or in a different format tomorrow, while a DAC purchased today is becoming obsolete faster than you can say “DSD1024” or “MQA v2”.
Let’s be honest, folks—the last thing we need is yet another audio codec.
Do you remember how perfect PCM digital was when it came out? Remember how it only took a new format to discredit the last? What are the hidden “problems” with MQA? My guess is that it will be only a matter of time before we start to see “flaws” in MQA too. I think “experts” will discover an “issue” with the way it folds audio into the “inaudible” band. Maybe it will cause “aliasing” problems. Perhaps the high bandwidth will cause, heaven forbid, jitter! It’ll be something cryptic like that. Some audiophile nerd will notice some anomaly on a spectrogram. And sooner than you know it, a new format will come along to replace it. My prediction is we’re only a few short years away from “MQA-pro”: a larger MQA file where the high frequencies are not folded into the audible band.
So please, let’s stop inventing new digital formats. I and many others are of the firm belief that PCM well implemented is more than adequate. Let’s stop reinventing the wheel. Brainy audio scientists, my sincere request to you… please start looking for something else. Something like the dramatic change from vinyl to CD. We need more leftfield thinking. Not another samey technology with 0.1% innovation, 99.9% marketing.TAGGED: audiophilia, hi-fiMODIFIED: 6th Jul 2021, 23:15