Digital Audio Players: Gapless Playback


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What is Gapless Playback?

Gapless playback is when a series of audio tracks are played seamlessly, one after another, without any pauses or clicks in between. Unwanted pauses or clicks between tracks can ruin pieces of music which are split across multiple tracks, especially in cases where the music is not silent at the split points.

A gapless digital audio player will neither insert nor remove silence between tracks; instead it will play an album exactly the same as a CD player would play the original disc.

What isn't Gapless Playback?

Gap removal is not gapless playback. Gap removal is when passages of silence on an original CD are removed during playback. It can be useful in a handful of cases -- think "secret tracks" at the end of albums -- but also often goes wrong and removes quiet or silent portions of music which are actually wanted.

Crossfading is not gapless playback. Crossfading is when the next track starts before the end of the current track, with the end of the current track fading out as the start of the next track fades in. It can be useful when using a player's shuffle-tracks feature but is usually undesirable when playing an album.

Gapless playback is not a feature; the lack of gapless playback is a bug, the same as it would be a bug to add a click or pause in the middle of a track. Unfortunately, many digital audio players fail to do gapless playback. Fortunately, the situation is improving.

Who needs Gapless Playback?

How much, if at all, you care about gapless playback depends on the music you listen to, on whether you tend to listen to complete albums or individual tracks, and on your personal tolerance for the problem itself. Some people are perfectly happy with "near-gapless" playback, where there's just a small click between tracks, and some heathens people are even happy with players which insert two-second pauses between tracks.

A wide range of music can be affected by non-gapless playback. Dance albums are often continuous pieces of music. Rock has many examples such as Abbey Road by The Beatles. Live albums often feature continuous crowd noise between tracks. Rap and hip-hop albums often have skits separating their tracks. Classical albums often divide different movements in a single piece into tracks and opera is similar. Even some Country & Western albums are affected by the issue -- that's how serious it is -- and back in 2002, when there were no known portable gapless audio players, ignoring compact disc, tape and minidisc which could only hold one album at a time, Hank "The Buffalo" Hicks recorded his seminal take on the problem in the song Dag Nammit, I Would Sell Both My Pigs And Stop Sleeping With My Wife And My Sister For An MP3 Player That Worked Right which reached #7 in the C&W chart. Which was nice.

Examples of gaps

(To be written.)

Why is Gapless Playback Difficult?

Before we can talk about gapless playback we need an idea of how digital audio players work and some of the challenges they face even before gapless playback is considered.

Memory versus Storage

People commonly confuse memory and storage. Storage is usually large and relatively slow. On a digital audio player, storage is where all your audio files are and the amount of storage is what determines the amount of music data you can carry around on your player. Memory, on the other hand, is usually much smaller than storage, but also much faster. Memory holds temporary information that goes away when you turn off a device. A player may have several gigabytes of storage, enough to hold several days or even weeks of audio, but only a few megabytes of memory, enough to hold only a minute of audio but, crucially, the minute of audio in memory is the minute of audio you're listening to right now.

The Loader and the Emitter

We can think of a digital audio player as having two parts which work together to play a single audio track. Let's call these the Loader and the Emitter.

(This is a huge simplification. In reality there may be a long chain of different components which do a number of different jobs. The key detail is that there is a chain where each component depends on the work done by the previous component. For our purposes we can pretend there are only two components in the chain, the Loader and the Emitter.)

The Loader's job is to read part of the audio track and put it into memory in a format which the Emitter understands. The Emitter's job is to turn what's in memory into sound signals which are sent to the headphones or line-out socket.

Bad and Better Players

Let's define two types of digital audio player: Bad and Better.

On a Bad player there may only be one block of memory. The Loader will load as much of the track as it can into memory. Once that is done the Emitter will then play back what's in memory while the Loader does nothing at all. If the track is too large to fit in memory then there will be a pause when the Emitter finishes as it waits for the Loader to get the next part ready.

On a Better player there will be a second block of memory which the Loader can read into while the Emitter is still playing from the first block. If the Loader works faster than the Emitter then, from the moment the first block of the data is ready, the Loader will remain one step ahead of the Emitter and the next part of the track will always be ready when the Emitter needs it.

Note that the difference between the Bad and the Better players is not the total amount of memory they have; instead, it is how they use it. Both players might have, say, 32MB of memory

As an analogy, imagine you are at a podium to deliver a speech and your notes are on ten folded-up pieces of paper. You don't have time to unfold everything so you get the first page ready, put it on the podium and launch into your speech. If you pause at the end of each page to unfold the next one then Jon Stewart might be telling jokes about your public speaking skills on The Daily Show. A better plan would be to start unfolding the next page in your hands as you're working through the current one from the podium so that you're ready to switch pages the moment you need to.

Buffer Underruns

Even when there are multiple blocks of memory it is still possible for something to cause the Loader to run too slowly, allowing the Emitter to catch up. This situation is called a buffer underrun and is a rare condition on dedicated audio players.

Buffer underruns usually happen because data could not be read from disk fast enough. On a portable this can be triggered by sustained physically movement which causes the disk to protect itself from physical damage by shutting down until the movement dies down. The problem could also be caused by a physically failing disk which has to be read several times to get an accurate result, or by an extremely fragemented disk which takes a long time to read because the data is physically spread out. On a computer system the problem can also be triggered by other programs doing so much disk access that the music playback program doesn't have a chance to read its data, as well as by playing music over a network connection which doesn't have enough bandwidth.

Buffer underruns can also be caused by trying to decode an audio file which requires more CPU power than is available. This is even more rare since most portable players won't even offer to play a file in a format they cannot decode and most computers, even when under significant multi-tasking load, have enough CPU power to decode every format. When playback glitches happen consistently in particular files it is less likely to be CPU power and more likely to be a corrupted file, a badly encoded file, or a file which has been encoded using a variant of the format which they player doesn't understand; all of which look the same from the player's point of view.

Gapless Problem #1: Being ready for the next track.

We haven't even talked about gapless playback yet because, so far, we've only talked about playing a single audio track. It is unlikely that a Bad player, with only one block of memory, could ever do gapless playback, but many Better players can't do gapless playback, either.

For a player to do gapless playback it has to tackle two problems, the first of which is being ready to start playing the next track when the current track finishes. When the player knows that the current track is about to finish it has to make sure that it starts work on the next track in advance, giving itself enough time to get everything ready.

From our high-level point of view this work is very similar to what the Better player, described above, does to ensure that large files can be played in multiple blocks. There are some complications, such as one-off processing which must be done at the start of each file, but these calculations are typically very fast and not a significant factor, at least with the MP3 format. (Some more complex formats formats, for example Vorbis, require significant computations before a file can start playing and this can make gapless playback difficult on a relatively slow processor. It is still entirely possible, though.)

In reality, whether a player succeeds at Gapless Problem #1 is usually down to software design rather than any of CPU power, disk speed and format complexity. This aspect of gapless playback should be easy to get right if the software developers keep it in mind from the start but most playback software seems to have been written with the over-simplified aim of playing just one track. Start the playback logic, play one track, then shut-down their playback logic, only to then realise there's another track to play and the playback stuff has to be started again. The system as a whole knew it had another track to play because the tracks are all in a playlist but the thing driving the playlist isn't talking to the thing playing the tracks.

It's like driving a car around a race track and turning off the engine at every single corner, only to realise there's more road around the corner and the engine has to be started again. It's incredibly stupid but it's exactly the kind of stupid situation you can find yourself in when programming if you don't pay attention to design and fail to consider things from certain levels.

When faced with a system which fails at Gapless Problem #1 the only options seem to be to re-structure large parts of the system or to attempt to make it play new files from scratch so fast that no human could ever notice the delay. Unless you're really lucky with your old code, re-structuring a program is a long, expensive process and requires re-testing the whole thing before you're done. Doesn't sound good, but the second option is probably physically impossible on any current hardware, given how small a delay people can detect.

MOOO! Everything below is old and not yet re-written.

Examples of gaps

There are thousands of albums out there that should be played back gapless. Incorrect playback matters more for some than others and a pause in one place may cause minor irritation while a pause in another may completely ruin a piece of music. The Beatles' Abbey Road is a classic, well-known example where the medley in the second half is ruined by incorrect playback. There are many more examples but let's pick a particular example to look at:

The transition from Track 6 (Parabol) to Track 7 (Parabola) on Tool's Lateralus album is a good test of a player's ability to do gapless album playback. The two tracks are really one piece of music and the transition happens at full volume. In this situation even a fractional second of silence is noticeable and, at least to me, very annoying.

Note: The recordings of the Karma and iPod below are intended to demonstrate each player's (in)ability to do gapless playback. They are not intended to demonstrate either player's audio quality. Both players have excellent audio quality but you can't tell from these recordings because they're done via the line-in on my soundcard, encoded at 64kbps, and in most cases have been through a lossy codec twice.

Here is what you get if you encode the two tracks to MP3, then decode them and join them together:

(click to listen; 109k)

You can see and hear that there's a small amount of silence between the tracks. This is probably caused by the encoder (LAME 3.9x) padding the end of the track with a bit of silence.

If you're looking at the graph and thinking you'll never notice that little tiny glitch then LISTEN TO THE SAMPLE and prove it to yourself.

The Rio Karma portable has features for gapless playback which enable it to detect the exact point where a track ends, either by reading a special tag inserted in the file or, if there is no tag, detecting a short, sudden drop to silence at the very end of the file. The Karma moves from one track to the next as if they were one file without so much as a click:

(click to listen; 120k)

Ogg Vorbis is an audio format like MP3 but with explicit support for gapless album playback, provided the device doing the playback does its job properly. With Ogg Vorbis, just as with MP3, the Rio Karma does not disappoint:

(click to listen; 128k)

Now let's look at the market leader, the Apple iPod. As you can see and hear the results are pretty awful:

(click to listen; 118k)

It doesn't matter whether or not silence is added by the MP3 encoder when the player is adding almost a second of silence all by itself. Even with a pair of WAV input files, identical to the original CD tracks, the iPod fails:

(click to listen; 124k)

The 3rd and 4th generation iPods may have reduced the gap time slightly but they have not actually fixed the problem. They still add their own silence on top of any silence added by the audio format.

Workarounds with MP3

Although part of the problem is MP3 itself, it isn't a lost cause. There are ways to do gapless playback with MP3:

  1. Create a single, large MP3 file for each album.

    • Truly gapless (unless your MP3 player is really stupid).
    • Cannot jump to or skip over tracks.
    • No track titles.
    • Cannot create playlists of favourite tracks, use random play feature, or decide you only want to carry a couple of tracks from an album without creating multiple encodings of it, which is a waste of space and time.
    • This is Apple's recommended "solution" and the ability to rip CDs into a single track was boasted as a new feature in a recent iTunes update. (It's an old, standard feature in any decent CD ripper, of course, but not one you should be forced to use for this purpose.)
    • Users with older iPods may be completely out of luck: I tried this on 2nd generation iPod (1.3 firmware) using 192kbps CBR MP3 and found it still added a half-second gap every 32meg. I guess it loads 32meg of data, plays it all, then loads the next 32meg, leaving you in silence while it loads. The concept of double-buffering -- using part of the buffer for playback while loading data into the other part, ready for a seamless switch -- is certainly not new and it's quite shocking that a multi-hundred-dollar music playback device doesn't use it. (Yes, my iPod, like every other HD-based MP3 player, has to minimize disk usage to increase battery life but that doesn't mean it should wait until the existing data is completely used up before loading more. Double buffering, done properly, causes very little power drain in reality.)

  2. Create a single MP3 file with a cue sheet.

    (One big MP3 file and another file which maps out the track times and titles.)

    The same pros and cons as above, except:

    • Can jump to and skip over tracks.
    • Can have track titles.
    • Very few things support using CUE sheets as bookmarks. Foobar2000 does support them. There's also a Winamp plugin but you end up with a second playlist window (one for albums, one for tracks) that wasn't very convenient when I tried it. One or two hardware players support cue sheets but almost all do not and you probably don't want to be tied to this method since it prevents you changing players in the future.
    • Didn't work with VBR MP3 compression last time I tried it.

  3. Crossfading.

    Crossfading can be a bit better than a sudden pause or click but it still completely ruins the flow from one track to the next on an album. Would you be happy if the player randomly faded out and then back in again in the middle of songs? I doubt it but that's exactly the effect crossfading gives with some albums.

    Again, if the artists had intended their tracks to be crossfaded they would have done that in the first place. Sometimes artists do mix their albums with crossfades but then if you play them back with crossfading you'll be listening to crossfaded crossfades which sound awful. Crossfading is great for a random-track, non-stop-music party-mix but that's something completely different.

  4. More intelligent encoders and playback software.

    The gaps between MP3 tracks are caused by three problems:

    1. MP3 encoding often adds small amounts of silence.

      As you can see in the first example image above, MP3 encoders can add a bit of silence to pad out the end of a file. Not all encoders do this in all situations but there are various technical reasons which make it difficult to avoid doing at least some of the time. It's probably something MP3 players are going to have to deal with to do gapless playback.

      Even very tiny amounts of silence are very noticeable to the ear so eliminating this frame-gap, as it's often called, is quite important.

      Some MP3 encoders, such as newer versions of LAME (at least in VBR mode), and encoders for other formats such as Ogg Vorbis, write a tag to the front of each file specifying exactly how long it is. This hint will help a player do gapless playback, provided it knows to look for it. The Rio Karma portable player does this. The free Foobar2000 software for the PC also does it, and there are third-party plugins for Winamp which do the same.

      In the absence of such a tag, intelligent playback software will decompres the MP3 data ahead of what is being played back and look at the end of each file. If a sudden drop to silence is found in the very last MP3 frame then it is removed and the result is usually continuity with the next track. Once again, the Rio Karma does this. I believe the Empeg in-car player does as well. Foobar used to do this (but I think Foobar2000 relies on the LAME tags exclusively now). Third-party plugins for Winamp attempt to do the same thing with varying degrees of success.

      No other hardware or software that I'm aware of deals with this problem.

      Note that this is NOT what Winamp's DirectSound plugin does when you enable the removal of silence at the end of tracks; that can remove far more than just the last tiny bit of pure, unwanted silence. It works based on a volume threshold which, if set wrong, causes quiet (but not silent) sections at the end of tracks to be skipped over. Several seconds of music can be skipped, making the "feature" a total disaster in my book.

      For a long time, iRiver promised that gapless playback woudl be added to their harddrive-based players. At the very end of August 2004 the much-delayed firmware finally arrived and turns out not to do gapless playback at all. Instead it does "Silence Removal", pretty much like the "feature" in Winamp's DirectSound plugin mentioned above. Initial reports from iRiver customers say it still leaves clicks and silence between music like Abbey Road, making it rather useless, but can also incorrectly remove up to ten seconds (!) of quiet music from the start or end of tracks, make it worse than the problem it's supposed to solve. iRiver are a company who released two CD players which could not play standard audio CDs gapless (one was fixed in a firmware update, the other never was), but I still find it quite surprising that they did such a bad job with the firmware, after taking so long to make it and with the Karma as proof that it could be done in a portable player, almost a year earlier.

    2. MP3 doesn't ensure continuity between tracks.

      MP3 is a lossy compression. The sound at any point in an MP3 may differ slightly from that in the original wave and if each MP3 file is created independently then there's nothing to stop the waveform at the end of one file being quite different from the waveform at the start of the next one, possibly resulting in a click during playback.

      The people behind the excellent LAME MP3 encoder seem to be experimenting with a new option which addresses this problem and/or the one above but it's undocumented at the moment. (LAME is an MP3 encoder now.)

      If you dig around in the Ogg Vorbis technical documentation you will find the recommendation that players, for any audio format, do some processing where tracks meet up in order to smooth over any discontinuities caused by encoders that haven't ensure the ends line up.

      In reality I have never noticed this effect and it's probably not worth worrying about, especially while other, larger problems exist.

    3. Most MP3 playback engines don't even try!

      Even if the above two things were fixed we'd still have problems because most MP3 players make things worse by not being ready to play the next track by the time the current one finishes. This cannot be blamed on the audio format or encoder. It's simply bad programming and there really is no excuse for it.

      Winamp was, years ago, almost as bad as the iPod but is actually quite good these days provided you set its output plugin (WaveOut or DirectSound) to buffer ahead on track change (500ms seems to do the trick). On some albums with current MP3 encoders Winamp is good enough, out of the box, that you can't notice the gaps; at worst you get the slight stutter due to MP3 frame-gap. That frame-gap is it's still noticeable and annoying in many cases. If it's just one track join, like Parabol/Parabola, and you're forced to use MP3 and Winamp or an iRiver or iPod then you can encode the two tracks as a single MP3 but it would be nice not to have to inspect each album you buy to see which tracks need combining, and some albums will need all of their tracks combining, resulting in that one big MP3 file again with all of the problems discussed above.

      Winamp 5, with the buffer-ahead setting from the paragraph above, will play FLAC and Ogg Vorbis gapless out of the box and there are third-party plugins for Winamp which address the issues of gapless MP3 playback with varying degrees of success. Gautam Bhatnagar wrote to me suggesting the MP3 Splice plugin and there are a few others; I'm not sure which is best. (It would also recommend you use the Winamp FLAC plugin that comes with the FLAC encoder/decoder package since it is much better than the one which comes with Winamp.)

      The Rio Karma (with recent firmware) and the Foobar2000 software player are two examples of excellent playback engines which deal with all the problems to give you the gapless album just like on the CD it came from.

Alternatives to MP3

So, gapless playback is possible with MP3, even on portable devices. What about some of the other formats?

  1. AAC

    I am told this format has the same problems as MP3 but I have not heard it for myself. Either way, no hardware I know of that plays AAC also plays gapless.

  2. Wave

    Don't compress the music at all, or use a lossless compression like FLAC (assuming your player even supports it), and you avoid the inherent problems with MP3. The obvious problem is that you can store a lot less music (with increased battery usage since the playback buffer needs refreshing more often). Of course, many players cannot even play this back without inserting silence between tracks.

  3. WMA

    Maybe on a computer but at the moment it looks like gapless playback of WMA is impossible on portable players, even the Karma, unless you get lucky. All portable WMA decoding code comes from Microsoft and cannot be changed by the companies who licence it, so it's up to Microsoft to support gapless playback. Until then, stay away from this format.

  4. FLAC etc.

    FLAC is an open, free lossless compression which cuts wave files roughly in half without throwing away any information. Unlike lossy codecs such as MP3, Ogg Vorbis, AAC, ATRAC and normal WMA, when you unpack a FLAC file it is identical to the original it was made from. FLAC also supports tags for artist, title, and so on and can be batch converted, tags and all, to whatever other format you want. Apple Lossless and WMA Lossless are both very similar to FLAC except that they are not free nor open but are instead owned and licenced (or not) by Apple and Microsoft respectively. Since the formats are lossless there are no frame-gap issues so any player which does its job properly and supports these formats will play them gapless. Of course, very few players do their jobs properly: The Karma will play FLAC gapless but don't expect an iPod to play Apple Lossless without pausing between tracks. The other problem, for portable audio, is that the files are huge and the size-quality trade-off probably isn't worth it unless your music collection is small. Still, portables will continue to get larger, and FLAC & friends are great formats for archival and computer use (see below).

  5. Ogg Vorbis

    Although they don't seem to make any kind of fuss about it, the Ogg Vorbis audio compression format supports gapless album playback and it works! It works on live albums. It works on Abbey Road. It works on The Fragile. It works on Pink Floyd. It works on Parabol/Parabola! It's completely free for anyone to use in their software or hardware and free to use for encoding. It compresses as well as MP3 with no quality compromise (the claim is it's better). Winamp supports it out of the box (see above) and it has reasonable hardware support (about as much as AAC). Of course, just because some hardware plays Ogg Vorbis files doesn't mean it plays them gapless (e.g. the iRiver).

    There are some downsides to Ogg Vorbis. At least with current generation decoders, it uses more computational power to decode, which translates to slightly lower battery life. (Karma can play MP3 for 16 hours but Ogg Vorbis for only 11 hours. That's a fair difference but still a decent amount of time and equal to the much celebrated playback time you would get from 2004's 4th generation iPods.)

    Ogg Voris also requires a significant amount of pre-computation before a track can begin to play. Using the Karma as an example again, this results in a slight delay when you hit play or jump tracks, instead of the instant response you get with MP3 files. (With MP3 the Karma will also buffer up the first seconds of the next few songs in the playlist so they're ready should you choose to skip to them, but this doesn't happen with Ogg Vorbis because the overhead is too great.) The pre-compuation overhead also means that gapless playback is more difficult and, compared to MP3, the player has to start working sooner to get the next track buffered up. In the case of the Karma the gapless playback actually fails very occasionally with Ogg Vorbis files, approximately one time in every hundred track changes, although this has only ever been reported when the Karma is playing a track for the first time. The theory, which hasn't been confirmed or denied, is that the extra work the Karma does after playing a track for the first time (it saves a little picture of the complete waveform, plus some other metadata) may sometimes take too long for it to get the next track started in time.

  6. ATRAC and Sony MiniDisc and Flash/HDD players

    Sony's ATRAC codec has always been gapless. The new Hi-MD format offers as much storage as the smaller HD players on changeable discs that allow you to scale how much music you carry around reasonably cheaply by buying more discs. Obviously, if you want a 40gig library then it becomes a pain to carry that many discs, but many people don't need that much so Hi-MD is worth considering. Battery power on MD players is still better than almost all types of MP3 player (at least those with moving parts) and Sony's newer flash players have stagering battery life quotes in the region of 50 hours. Their players tend to be reasonably small and quite rugged.

    That all sounds pretty good, doesn't it? Unfortunately, there's one major downside to all of Sony's portable music players: SonicStage. SonicStage is Sony's software for putting music onto MiniDisc and, by all accounts, it completely sucks. You have to use SonicStage for transfering music as manually copying to the device does not add the files to the music library. SonicStage is slow and badly designed and generally people seem to wish it wasn't there.

    Sony's newer players finally support MP3 (without having to transcode) in addition to ATRAC but gapless playback only works for ATRAC and even then you must rip the CD using SonicStage. This means that you have to go through the slow, tedious process of ripping all your music if you want it to play gaplessly on a Sony. Even if you've got lossless rips of your music collection you will still have to at least write each album to a virtual CD and fool SonicStage into ripping it. SonicStage won't even produce a gapless album if you have locally stored ATRAC files; the input has to come from a CD. Lame.

Future-Proof your Music

If you care enough about your music that you're reading this page, you probably want to make sure that whatever format you buy or convert your music to is going to last you into the future. Here are a few suggestions. Take 'em or leave 'em.

Refuse to buy DRM'd music.

The big record companies only want to sell you music online if they can control what you do with it via Digital Rights Management. In principal, I don't have any problem with them using technology to prevent piracy, but DRM takes away significant rights and choices from consumers and should, in my opinion, be boycotted. There is no one standard format for DRM'd music. The iTunes store will sell you AAC files wrapped in a proprietary FairPlay DRM wrapper. While AAC is a standard format supported by a semi-reasonable number of players, the FairPlay DRM wrapper around it is owned by Apple. Except for HP who are making iPod players to meet demand, Apple have refused to licence FairPlay to anyone, whether they want to sell DRM'd music compatible with iPods or make competing music players which can play music bought from iTunes. Pretty much the only other popular DRM'd music format is WMA. Many more online stores and music players support DRM'd WMA files, but not all of them do...

Do you really want to pay money for some music that starts making choices for you about which hardware and software you play it back on in the future? What if you buy a DRM'd WMA album today and next month a kickass new iPod comes out that can't play it? Do you skip the iPod, or buy a second copy of the album? If you buy music from the iTunes store you'd better be really, really sure that for the rest of your life you're only going to buy Apple music players because it looks likely right now that nothing else will play them, HP's version of the iPod aside.

Of course, DRM, like any software-based protection can be broken and worked around.

The crudest, and worse, workaround is to sample the soundcard output while the music is playing. This obviously leads to pretty awful quality. A slightly better idea is to burn the music to a standard audio CD, which most DRM licences allow, and then rip the CD and compress it to some other format. Aside from wasting a CD, this will still reduce your audio quality because, unless the original DRM'd music was bought in a lossless format, it will have been through a lossy encoder twice and this reduces audio quality. (Although it's technically very different, you can think of each lossy compression as a recording to old fashioned cassette tape. Each recording-of-a-recording will have slightly degraded quality and the same thing happens when you re-compressing music with lossy codecs like MP3, AAC and Ogg Vorbis.)

There are more sophisticated ways to unshackle your music from DRM systems which involve tools written by clever people which break the protection and give you a plain AAC or WMA file as a result. The legality of using, or even talking about, these tools varies greatly around the world, depending on how much influence the record industry has over your local authoritarian corporate-led sellout piss-poor excuse for a supposedly-elected-for-the-people government, but they are out there if you look for them, and they're supposed to work quite well. You'll still be stuck with an AAC or WMA file at the end of it, but at least you'll be able to play it on a wider range of hardware/software.

Store your albums in a Lossless Format.

Ripping hundreds of CD is a pain in the ass and, if you have a sizable collection that you want access to on your computer, is best done once and once only.

New and better audio compression formats come and go. Even within a given format, over the years better encoders come along which improve the quality and or filesize of what they produce. Remember when 128kbps CBR MP3s seemed great? Then 160kbps seemed like a better idea. Then VBR encoders came along and that sounded like a good idea so you used them. Then you realised some stuff sounded awful with VBR so you switched to 192kbps. Now the VBR encoders are a lot better so it's worth using them to get higher quality from the same filesize. Now there's also Ogg Vorbis, AAC, MPC and other audio formats... You really don't want to spend a weekend re-ripping all your CDs every time a better audio format comes along, nor do you really want to store all your music in AAC, WMA, Ogg Vorbis or some other format that your current portable player supports but your next one might not.

The answer is lossless compression. Use FLAC, which is free and open and can be plugged in to virtually anything. Use Apple Lossless, which isn't open but is trivial to use if you're an iTunes fan. Use WMA Lossless, which also isn't open but is trivial to use if you're a Windows Media Player fan. It doesn't really matter which one you use because they all have the same compression levels (about 50%) and they all support tagging your music with artists, titles, and so on. Since they're lossless you can convert from one to the other if you have reason to later. The important thing is that you have on your harddrive an exact copy of what's on your CD. You can then convert it into whatever lossless or lossy format you need to when it comes time to put it on a portable. If you need to convert your music to another format tomorrow you can do it in a batch overnight and not have to waste days re-ripping CDs, getting those problematic ones to read in you CD-ROM, tediously correcting tags set by the awful online databases, and so on. The only price you pay is harddrive space but, if you've looked recently, harddrives are dirt cheap. 300meg per album instead of 60meg? So be it. My time is worth more money than the disk space.

All the advertising and articles I've seen suggest the iPod is god's gift to mankind; it must support some of those workarounds and alternatives, right? It's an expensive device specifically made to play music; surely it does the job properly?

Nope. Apple seem more intersted in the way the iPod looks and peripheral features such as address and phonebooks than the ability to play music, despite people sending them complaints for years now.

I admit: I was suckered. I hadn't seen a single complaint about the iPod (these days I know where to look :-/). All the advertising and articles made it sound fantastic. It was an expensive device. It was made specifically to play music. I was sure they would have made it able to play albums properly -- it seems a basic requirement of a music player to me -- and so I bought one. For 300 ($500). How wrong I was. If you care about album playback then don't make the same mistake I did and definitely don't rely on the fact that Apple may one day improve their firmware because they don't seem to care. Still, the iPod does look pretty cool so if that's all you're worried about then go for it!

To be fair, most other hardware MP3 players are just as bad at gapless playback as the iPod, and many people who don't care about the issue love their iPods. The iRiver players can't do gapless playback. One of their CD players can't play audio CDs gapless, which is a joke. Even Rio, who produce the brilliant Karma, continue to produce a whole range of lesser players that fail to do gapless playback. In short, the DAP industry is a bit lame at the moment and has a long way to go before it's taken seriously by people who take music seriously. It's just that the iPod is the most expensive, the iPod is the one we're all told is the best thing ever made, it's the market leader by a long shot, constantly mentioned and shown gratuitously in the news to the point of utter irritation, white headphones worn with pride like a status symbol by millions of sheep on the train every morning, and the one I wasted my own money on only to discover it's stupid, expensive toy with hacked-together firmware made by a company with its head firmly up its marketing department's arse... Not that Apple don't make some cool computers; I have nothing against them, I just wish people would get a bit more objective about the other things they make and the iPod in particular.

(I shouldn't have to say this but a few people have written to me about it so here goes: iTunes, the program you use to play music on your Mac or PC, may well be able to do gapless music playback. I don't use it so I don't know but I'll take your word for it, although people on HA say it can't and I'm more likely to believe them. Either way, this has absolutely NOTHING to do with what the iPod can or cannot do. The iPod does not run a little copy of iTunes inside of it; it's music playback engine is COMPLETELY different. Hope that clears it up. Thanks.)

There's an online petition you can sign if you want Apple to fix gapless playback in the iPod.

Which portable player should I buy if I care about gapless album playback?

I decided to replace my 20gig iPod with something that had the same storage capacity (or better) and which did gapless playback of albums and supported the Ogg Vorbis format. The Rio Karma was the clear winner. In fact, it was the only player that did all that I wanted.

  1. Rio Karma

    The Karma seems to have been discontinued, pending the follow-up, long-delayed Chroma. You can still buy Karmas in some shops. I am still using mine and the only wish I have is that it had more than 20gig (it's possible to put a 40gig drive into it if you're brave). If my Karma broke I would still buy another one tomorrow because it's basically still the only music player that does the job properly (without the hassle of SonicStage), in my opinion, and I've yet to hear a better sounding portable device, either.

    The Karma does gapless playback of MP3, Ogg Vorbis and FLAC. Ogg Vorbis gapless playback can, very occasionally, go wrong the first time a track is played (see above), but even on those rare occasions it's still no worse than any other player. There also seems to be a subtle issue with gapless MP3 playback where there is a very, very small portion of the next track cut out, at least in some cases. The MP3 issue is usually not detectible as the cut is a tiny fraction of a second which is hard to hear in most transitions -- indeed only discussed in the forums when the Karma was a year old and none of us had noticed it before -- but there are some tracks where it can be heard easily, at least if you're looking for it. For example: On Abbey Road when Polythene Pam becomes She Came In Through... you may notice a beat, and the very start of the first guitar chord, is dropped. This may become an irritation and after the issue was discovered I went back to Ogg Vorbis on my Karma. (The MP3 rips were done using EAC/LAME and play perfectly in Foobar2000.)

    The sound quality is superb and the 5-band equaliser can add demonic levels of bass without any distortion, which is often overlooked in portable players. (The iPod also had good quality sound and bass, to its credit, but the equaliser was nowhere near as good.) The Karma has a bunch of other cool features such as RCA line-out on the docking station (so you can plug it in to your speakers), Ethernet as well as USB1 & 2 (as fast as Firewire), flashing lights :-) and a much better, more informative and configurable display and user interface compared to the iPod (in my opinion)...

    Some of the people who make the Karma are active on various Internet forums and provide extremely useful technical information as well as actually listen and talk to people about their suggestions and issues.

    Sounds too good to be true, doesn't it? Well, there are some buts... Quite a few people have experienced harddrive failure, which seems to be an issue with the Hitachi drives the Karma uses. A smaller number have also had the scroll wheel break off. (I've had mine for 9 months now without a single problem but other people have had two units fail on them in the same time.) Accurate failure percentages are impossible to know, since none of the DAP makers publish such details, but, although it's not really an excuse for anyone, it's an unfortunate fact that high percentages of all portable MP3 players from all manufacturers (and I mean all!) have hardware problems. The main variation is how companies deal with the problems. If you're in the USA my advice is to buy an extended warranty from your place of purchace since otherwise you only get a 90-day warranty and you have to deal with Rio if something goes wrong. All accounts of dealing with Rio customer services suggest it's something best avoided, to be honest, so an in-store warranty is a good idea, not just to get more than 90 days. If you're in the UK then there's no need to worry about any of this since you get a minimum 1-year guarantee from your place of purchace, by law.

    I've had zero problems with my Karma but even if it did break out of warranty I'd still buy another one because, as far as I'm concerned, other music players (which have similar physical fault levels anyway) are broken out of the box by their inability to play albums properly. As far as I'm concerned, other players are guaranteed not to work whereas Karmas tend to work. If you look on the web you'll find pretty much equal anecdotal evidence of hardware failures for every type of harddrive-based DAP, be it iPods, iRivers or Karmas. It's just you have to go through more hassle if a Karma dies and you're in the USA without a third party warranty.

  2. Other Rio Players

    The Karma, and probably the coming follow-up Chroma, are their only players which do gapless playback. Other Rio players do not do gapless.

  3. Sony flash and harddrive-based players

    According to a review on The Register, the new models which support MP3 will also do gapless playback. I'm not certain if they'll play MP3 without gaps or only manage it with ATRAC, but if you've got your music stored in a lossless format it doesn't really matter. You'll have to use the awful SonicStage software but it's nice to hear that there will be more choice in gapless hardware soon. Sony have released a firmware update for their Vaio Pocket flash players which reportedly adds gapless playback.

  4. iRiver

    The iRiver harddrive-based players seem to have similar specs to the Rio Karma and now support Ogg Vorbis but they do not play it gapless. The firmware update which promised gapless playback was finally released and turned out to be a complete joke that doesn't work. (See above.) Very annoying for those who had invested money into iRiver players and waited so long for the promised feature. Maybe they will realise their mistake and correct it, but I wouldn't recommend holding your breath.

  5. iPod

    In case you haven't got the message already, the iPod, the iPod Mini and even the very latest 4th generation iPods with fancy wheel on the front and oh-so-improved (hah!) battery life cannot play gapless music to save their fashion-victim behinds.

  6. Creative

    I've heard mixed information about the Creative players. It seems they are "almost gapless" in that their gap is small but they are not actually gapless.

  7. RCA Lyra

    A friend in Asia tells me his RCA Lyra MP3 player does gapless MP3 playback, at least on his mix albums. I don't know a great deal about them, and they're not available where I live, but they may be worth investigating.

  8. MiniDisc

    Will do gapless but with some pretty major downsides. See the file formats section above.

  9. Others...

    There's a list of hardware which supports Ogg Vorbis here: Just remember that Ogg Vorbis support doesn't guarantee gapless playback.

Update History

  • 4th January 2004
    First version. (Finally got annoyed enough to write all this down.)
  • 20th January 2004
    My Rio Karma arrived and the gapless playback works! Added info about the Karma and Foobar2000 both being able to play MP3 gapless, despite the inherent problems with the format. Added example recordings and graphs of the iPod being crap at playback and the Karma doing it properly.
  • 21st January 2004
    Tidied things up a bit. Changed example MP3s to 64kbps to save bandwidth (they still do their job just as well).
  • 1st September 2004
    Big ol' update.
    Added some details about iRiver's long-awaited, just-released, complete-and-utter-failure of a firmware update. (There I was, thinking that if two companies made players that worked properly maybe it would mean the whole industry would wake up and fix the problem in all future products. Now I'm worried again that my children will grow up thinking The Fragile has one-second gaps between each song, and isn't it weird, daddy, how the start of each track sounds a bit like the end of the previous one...)
    Corrected a bunch of minor things (in particular the stuff about LAME VBR track-length tags).
    Added some extra detail and removed some old/unnecessary detail here and there.
    Added some side-points / rants about DRM and lossless codecs.
    Moved some of the vitriol around slightly. :-)
    I expect it's full of typos and terribly constructed, rambling paragraphs right now. Sorry about that. You know how it is, reading something right after you wrote it. Thought that counts, and all that. Goodnight.
    Update-update: Added stuff about MiniDisc/ATRAC that I forgot about before.
  • 19th December 2004
    Minor update to add mention of Sony's new, and allegedly gapless, HD-based players. Also added a link to an online petition asking Apple to fix their iPods.

Thank you!

Thanks for reading this page and making it worth writing. Thanks to everyone who cares about this issue as much as I do for making me feel less like an obsessive-compulsive psycho. Turns out more people care about it than I first thought, and thanks to all those who took the time to write a thank-you email (they're not expected but I appreciate them). Thanks to those who have provided additional details and corrections. Thanks to those who spread the word about the issue or the page itself or both. It's not the end of the world if our music has some gaps in it but it still sucks so let's try to do something about it.

Get DOpus Now! Image and audio bandwidth provided by GPSoftware, makers of Directory Opus. (Ta Jon! (Even if you did buy a Nano. :-)))


A short section of Tool's Parabol/Parabola is used to demonstrate gapless playback abilities. These tracks are (C)2001 Tool Disectional, L.L.C./Volcano Entertainment II, L.L.C. and are used here under the assumption that it is fair-use to use a small section of them for demonstration purposes. If you have a problem with this then please email me and I will replace them with some other demonstration.