14 Replies Latest reply: Oct 3, 2010 3:12 PM by turingtest2
ron App Level 1 Level 1 (15 points)
Every time launched, iTunes 10.1 is determining "Gapless Playback".

Technically, there is no such thing as gapless playback. There are just tracks which have to be played as they are - without adding any gaps between them.
There are antique programs though (early iTunes might have been like that) and devices (early iPods) which were unable to play tracks without adding "gaps" between tracks, and then next version with "gapless" playback was like a big thing.

So what, now mythical "gapless playback" is a nostalgic contribution to those times, or somebody in Apple has no clue what the music player should do?
Apple's own kb/HT1797 says that gapless playback is "always on", which means iTunes is able to play tracks properly. What to "determine" then?

This is not an anti-apple joke or something.
Selling individual tracks from albums in Apple store (I have always seen this as an evil; imagine selling chapters of the novel separately) can twist one's mind to the level where understanding of how music has to be listened, disappears.

MBP i5 2.53GHz, Mac Mini 2,1 (2GB), Mac OS X (10.6.4)
  • Natboy Level 1 Level 1 (0 points)
    I would also like an answer to this. This particular feature seems to stop my iTunes from launching. I can't shut it off, I can't see my library I have just readded. And all I get to see is "Analyzing 108 of 12097:......" When what I want is to be able to use my iTunes. ******** is what it is.
  • Jolly Giant Level 7 Level 7 (25,440 points)
    [_*What is Gapless Playback?*|http://support.apple.com/kb/HT1797?viewlocale=enUS]

    JGG

  • ron App Level 1 Level 1 (15 points)
    Jolly Giant wrote:
    [_*What is Gapless Playback?*|http://support.apple.com/kb/HT1797?viewlocale=enUS]


    Thanks, I know that article, I even mentioned it in my original message, but it does not explain anything.

    Well, article says that "gapless playback" is always on, and that is good - would be rally weird to add gaps to the music. What would you say if there was *noiseless playback, meaning no additional hiss and clicks would be added to your music, and then iTunes would determine noiseless playback every time when started?

    So - there is nothing to determine, just play tracks as they are.

    Then, there is a potential issue with crossfade. But, how iTunes could possibly know in what order I am going to play tracks? How it could possibly "determine" anything upon startup?
    Normally, it means nonsense. But, if there is any reasonable meaning in all this, I would like to know.

    So, once again - what is that what iTunes is actually "determining"? What is that what any one in his right mind would want to "determine" upon loading the music library in the player?
  • turingtest2 Level 9 Level 9 (53,700 points)
    The original mp3 format uses fixed size data frames so any given track might have a small amount of silence encoded at the end of it. Not a problem if the mp3s are distinct tracks ripped from a CD which normally include about 2 seconds of silence at the end of each track, but noticible if the tracks are meant to play continously. The transistion from one track to another needs to managed carefully if the original gapless effect is to be recreated. Obviously if you're playing two tracks that are not sequential on an album, or tracks from different albums, it doesn't matter. However if cross-fade is enabled and the transition is from one track to the next on the same ablum and they are marked as *Part of a gapless album* then instead of a cross-fade you want a smooth gapless transition. This is the point of marking the tracks so that iTunes knows ahead of time which effect to go for and hence why iTunes performs its "Gapless Playback Analysis" after import.

    Note that while the articles clearly state that the setting only affects the behaviour of iTunes I have sometimes found some benefit for gapless transitons on my iPod if I disable and then reset the *Part of gapless ablum* option. My assumption is that iTunes is caching information about the gapless transition for the iPod so that it doesn't need to be analysed on the fly during playback. Occassionaly reworking that analysis has a positive effect.

    tt2
  • ron App Level 1 Level 1 (15 points)
    No amount of analysing is going to give the answer how much silence is added to the track. Normally this info is embedded in metadata and player just trims it off. Even if analysis and determining could give that answer, just embed it in metadata and use, it is not going to change.
    And, regarding crossfade, again - iTunes has no way of knowing in which order you are going to play tracks.

    If you iPod behave in such a strange way, there must be something wrong.
  • turingtest2 Level 9 Level 9 (53,700 points)
    No amount of analysing is going to give the answer how much silence is added to the track.

    Read this for some more info: http://en.wikipedia.org/wiki/Gapless_playback

    I guess that, unlike me, you're not old enough to remember early PC media players that couldn't do gapless playback on the fly, the relief when they finaly came along or the disappointment of early portable devices that again couldn't do it.
    Normally this info is embedded in metadata and player just trims it off.

    I don't know that it is. You're assuming there is an agreed standard as to how to encode the information that is in use by all media players. Different playback software possibly needs different information in order to know just when to start preprocessing the next track or how to manage the data from the two different streams.
    Even if analysis and determining could give that answer, just embed it in metadata and use, it is not going to change.

    The assumption that the answer is not going to change holds only if no changes have been made to the algorithm or the track-order of the album since the tracks were first imported and that iTunes identified the tracks as gapless to start with. iTunes often fails to correctly group and order tracks when first imported, an issue I deal with here - http://samsoft.org.uk/iTunes/grouping.asp - and there have been plenty of new builds during the time I've been using iTunes.
    And, regarding crossfade, again - iTunes has no way of knowing in which order you are going to play tracks.

    But while playing the current track it knows which track it is about to play next... If that track is the next seqential track from the same album and crossfade is enabled and the (current|next|both?) tracks are marked as gapless then crossfading will be ignored in favour of gapless transition.
    If you(r) iPod behave in such a strange way, there must be something wrong.

    My iPod is fine thanks, while my findings are necessarily subjective I'd hoped you would find it a useful indication that iTunes is doing something when it claims to be doing "Gapless Analysis" and that, just possibly, that something might even be related to the final user experience.

    tt2
  • ron App Level 1 Level 1 (15 points)
    turingtest2 wrote:
    I guess that, unlike me, you're not old enough to remember early PC media players that couldn't do gapless playback on the fly, the relief when they finaly came along or the disappointment of early portable devices that again couldn't do it.

    I guess you are wrong . Those players were just poorly designed, many of them couldn't even play lossless without introducing gaps.
    Regarding wiki/Gapless_playback, I know all that and more. And, if there is unknown amount of silence before/after the track, there is NO WAY how to "determine" that with any kind of analyzing, except comparing with known actual track.
    But certain encoders (like Lame3.90+) include necessary information in the metadata. Assuming that iTunes has some *magical way of calculating this information without relying on this metadata, it would make sense to add this info to metadata, not determine every time when iTunes starts.

    ...and that iTunes identified the tracks as gapless to start with.

    Again, there are no such thing as "gapless". Gapless only applies to properly encoded music, as opposed to flawed original mp3, and of course, to way of properly playing the music against introducing pauses(due to poor design) like in early iPod.
    iTunes does not have to identify anything, except if the next song belongs to the same album than previous. And you don't do that at launch.

    But while playing the current track it knows which track it is about to play next...

    Again, I am talking about "determining gapless playback" when iTunes starts, every time...
  • turingtest2 Level 9 Level 9 (53,700 points)
    Aha "detemine every time iTunes starts" is a very different kind of problem from "what is gapless playback?" iTunes is supposed to perform this magical analysis on a one-time basis. It should do it as a one-time pass, in a background process following import. If it is doing it every time you start iTunes then I guess something is going wrong when iTunes tries to save the results of the process or it is crashing out before completing.

    I haven't any personal experience with the problem but it would seem to be a persistent issue for a minority of users since introduced in iTunes 7 some three years ago. Looking around the web there is a slight hint that it may be caused by specific problem files, however the only way of testing would be to create a second test library and import your media in stages to see if and when the problem reoccurs.

    tt2
  • ron App Level 1 Level 1 (15 points)
    Actually, I am not trying to solve the problem (I don't need iTunes 10 anyway), but to clear things - haven't seen anything like that before, and problem is only linked to iTunes 10 update. After reverting back to 9.2.1, "determining" has again disappeared. If it was some kind of problem with saving info, I would normally expect an error message or something.
    Also not really trying to discuss theoretical possibilities of gapless playback.

    What I want to know is - what exactly is iTunes doing when it says it is "determining gapless playback".
  • turingtest2 Level 9 Level 9 (53,700 points)
    ron App wrote:
    Actually, I am not trying to solve the problem (I don't need iTunes 10 anyway), but to clear things - haven't seen anything like that before, and problem is only linked to iTunes 10 update. After reverting back to 9.2.1, "determining" has again disappeared. If it was some kind of problem with saving info, I would normally expect an error message or something.

    You're optimistic... iTunes is particularly bad at error reporting either giving no feedback at all (e.g. silent fails to update information) or obscure error messages which often don't reveal which files it has had a problem accessing.
    Also not really trying to discuss theoretical possibilities of gapless playback.

    What I want to know is - what exactly is iTunes doing when it says it is "determining gapless playback".

    Exactly? Who knows? Since Apple have chosen not to make it explict in their support documents we're left with deduction. If you take a random selection of tracks and import them into iTunes you should find that, following import, some are marked as *Part of gapless album* and some are not. My guess, is that it's trying to guess how to behave in different circumstances (e.g. when cross-fading should be avoided) and, where necessary, do what ever pre-analysis might help with gapless transitions. When it works nobody notices, but if it goes wrong it causes problems. Personally I recall disabling cross-fading features in older software like Winamp because they would do the wrong thing for gapless transitions and that was always much more annoying than a slight gap between unrelated tracks.

    tt2
  • ron App Level 1 Level 1 (15 points)
    turingtest2 wrote:
    ..following import, some are marked as *Part of gapless album* and some are not.

    Well, this is exactly the thing I do not understand.. because there are ONLY gapless albums out there, to my knowledge. There are only songs that belong to same album, and ones that do not, but that is easy to determine "on the fly".
    Therefore - there is nothing to determine. If this determining would mean analyzing some kind of mp3 album properties related to gaps - other story, but it is unlikely.

    Therefore, knowing how other illogical things are done in iTunes 10, I am a bit worried if is not indeed trying to calculate all possible song combinations in the playlists or something equally strange.
  • turingtest2 Level 9 Level 9 (53,700 points)
    ron App wrote:
    Well, this is exactly the thing I do not understand.. because there are ONLY gapless albums out there, to my knowledge.

    I've a horrid feeling we're going around in circles each not understanding the other.

    An alternative way of looking at things is that some tracks are meant to blend gaplessly into the next one while others come to a definite end, whether abrubtly or by means of a fade out, followed by a bit of silence or gap, and then the next track.

    Ideally a crossfade feature should not attempt to blend continuous tracks but it would be nice if it could remove unwanted silences between tracks (even those on the same album) if the user wants to use the feature. As far as I can tell the *Part of gapless* setting records and controls this aspect of iTunes behaviour but, short of asking the user what value should be used for each track, iTunes has to have some automated process for determining the initial value. I don't know why iTunes can't make this "to crossfade or not to crossfade" decision on-the-fly but given the property is there and editable it doesn't appear able to do so yet.

    The best guess I have is that iTunes is setting this property while doing the job it describes as "Performing gapless analysis". Again my guess is that not only is each track assigned a binary value for *Part of a gapless album* but also, where necesary, iTunes records some extra data which will subsequently let it, or supported devices, manage gapless transitions smoothly.

    BTW This feature isn't new to iTunes 10 and dates back to iTunes 7.

    tt2
  • ron App Level 1 Level 1 (15 points)
    turingtest2 wrote:
    An alternative way of looking at things is that some tracks are meant to blend gaplessly into the next one while others come to a definite end, whether abrubtly or by means of a fade out, followed by a bit of silence or gap, and then the next track.

    But track is still the whole, "gap" is not separately attached, it is a part of the track and therefore not for iTunes to determine how it is to be played. It has to be listened as artist/producer intended.

    Ideally a crossfade feature should not attempt to blend continuous tracks but it would be nice if it could remove unwanted silences between tracks (even those on the same album) if the user wants to use the feature.

    I strongly disagree, for me that would be a rape of music. Then not far to adjusting levels, changing tempo or something like that.

    As far as I can tell the *Part of gapless* setting records and controls this aspect of iTunes behaviour but, short of asking the user what value should be used for each track, iTunes has to have some automated process for determining the initial value.

    Would be not a concern if it would happen only with cossfade enabled. But I have never used crossfade, therefore this sudden "determining" looks worrying to me.
  • turingtest2 Level 9 Level 9 (53,700 points)
    ron App wrote:
    But track is still the whole, "gap" is not separately attached, it is a part of the track and therefore not for iTunes to determine how it is to be played. It has to be listened as artist/producer intended.

    The "attached" gaps are not the problem... Add an extra 2 millseconds silence due to issues with how lossy tracks are encoded and reproduced and it is only a problem *when there isn't supposed to be a gap!*.
    I strongly disagree, for me that would be a rape of music. Then not far to adjusting levels, changing tempo or something like that.

    I don't use crossfade personally, but say you're playing music at a party - you might want it played without gaps whcih is what the crossfade is trying to achieve. If you want it played without gaps you might want it to crossfade tracks in your playlist whether they've come from the same album or not. However I don't think you'd want tracks that normally play gaplessly to have an artificial and unecessary crossfade. Since you don't need the feature the details hardly matter however all but the simplest software contains features which some users won't want or need - just ignore them.
    Would be not a concern if it would happen only with cossfade enabled. But I have never used crossfade, therefore this sudden "determining" looks worrying to me.

    Well, as I said, iTunes has been doing this since version 7. With small numbers of tracks it probably takes a few seconds and happens after the getting album artwork thread. If it is done quickly enough then iTunes may not bother to put a message in the notification area. If you upgraded to version 10 and then rolled back you might have triggered it into reanalysing the entire library. If you let it finish the job, and there aren't any other issues, it should only have to do it the one time.

    tt2