Is Shuffle Really Random?

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Level 1

7 points

Is Shuffle Really Random?

Hey all,
My iTouch (and iPhone) have 14GIGs of music on them, but quite often in a 20 minute drive (on shuffle) I hear +two songs+ off the same album. Now, there's thousands of songs to choose from in a random rotation, how can it possibly play two from the same record in a matter of 20 minutes? Once, sure, but this happens quite often.

For instance, there's a Talking Heads album that it likes A LOT. I mean I hear something from that particular album almost every time I take a drive.

Just curious, but does anyone know what algorithm they use? This is too much of a coincidence for it to be truly random. There's songs on there I've never heard, while some have gotten 6-10 plays. (all songs are unrated)

3GS 32 gig, iOS 4, Wonky ios4 WiFi

Posted on Aug 25, 2010 3:59 AM

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Answer 1

Top-ranking reply

drumboi88

Level 2

435 points

Sep 28, 2010 12:50 AM in response to mugwamp

I read that the shuffle algorithm actually has variables that prevent it from being truly random. It's supposedly like genius, and I believe this is true. The shuffle will take all the songs you want to shuffle and attempt to pick songs of opposing "values". Let's say you have an album of 10 songs:

Track 1 : 7 plays.
Track 2 : 0 plays.
Track 3 : 14 plays.
Track 4 : 22 plays.
Track 5 : 4 plays.
Track 6 : 9 plays.
Track 7 : 1 play.
Track 8 : 25 plays.
Track 9 : 15 plays.
Track 10: 29 plays.

The shuffle looks at the amount of plays you have, and attempts to pick (at random) a song of high plays, and a song of low plays. Now, effectively, it's trying to get you to listen to songs you haven't heard with ones you have. Another thing it looks at is the most recently played. Let's say you heard Track 7 once, but it was over 3 months ago, and Track 5 was heard only 30 minutes ago. Track 7 automatically is higher target because of low song count and oldest song heard, making it prime to pick after a song like Track 10, which was just heard.

The other portion of the algorithm is supposed to be based on artist and albums. If an artist has a high track count (45 songs out of a possible 200), obviously it has a higher chance to get picked. The chances improve based on those tracks play counts in comparison to the rest of the library.

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Answer 2

Aug 25, 2010 11:00 AM in response to mugwamp

If the algorithm were truly random, it would be possible for an entire album to play in order. So what you're seeing is perfectly "random". What shuffle does is put all of your songs into a playlist in a pseudo-random order. As long as you keep playing, it will play each song only once until it has run through all of them. If, however, you stop, navigate to another playlist or play something else, Shuffle will generate an entirely new playlist the next time you select it. In that case, you may here the same songs you heard the previous time you selected Shuffle. Or you may not.

You can avoid some of this be setting up a smart playlist with the criterion: Last play is not in XX (e.g.30)days. Make sure live updating is selected. Then, put that playlist on Shuffle. Songs will drop off until it has been more than XX days since they were playled.

Best of luck

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Answer 3

srich1

Level 1

1 points

Sep 27, 2010 8:44 PM in response to mugwamp

I too wondered about the randomness of random. Here's a few of thoughts from my experiences.

One time I discovered I had the same song on a different albums, so I unchecked one of them in the library so it wouldn't sync.

Another time, I discovered the random 'shuffle' stopped shuffling and began playing alphabetically when it was connected via a usb accessory that was powered down or unplugged and but then powered up and remotely choosing 'play'. Although the ipod continues to play the song it had been playing during the shuffle, the very next song was in alphabetical order and that's when I discovered an identical song or song title. To prevent the shuffle to alphabetical I connect the ipod only after starting the car or powering the accessory.

Lastly, it also has been my experience the shuffle on my ipod seems to favor particular songs, but never during the same shuffle session. One time I heard 'Cold Turkey' by John Lennon nearly every time I started a new shuffle session even though there were about 500 songs from which to choose.

I've learned to live with it by just skipping the song.

Thanks to the other folk on this thread for the tips too.

Best of luck

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Answer 4

Aug 25, 2010 5:50 AM in response to mugwamp

I can't tell you anything about the algorithm, but I agree it's not very random. One of my play lists has 11% of its songs from a particular artist, but it's typical for it to play two of hers in a row, and once I got three out of five--with the other two being from a single other artist. Another artist represents 14% of that play list, and comes up much less often.

I do know that if you set up a play list to select songs that are least-frequently played, it does not choose randomly among those at the bottom. For example, suppose you set up a list to "randomly" pick 20 of your least-played songs, and you have 100 songs with a play count of 0. It'll take those 100 songs, arrange them in reverse alphabetic order by artist, and then give you the first 20 on the list.

To avoid hearing the same songs over and over, I've created a smart play list that gives me a random selection of least-played songs, and then I shuffle that. It took some doing to overcome the issue in the preceding paragraph.

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Answer 5

Aug 25, 2010 11:31 AM in response to IdrisSeabright

Yes, a truly random shuffle of a 15-track album could result in all 15 tracks being played in order. But that would be expected to happen about once every 1.3 trillion plays. Look at it another way, if you were playing poker and your opponent dealt himself five royal flushes in a row, would you think he was lucky or cheating?

I mentioned only a couple of unexpected "random" shuffles, and certainly those would not be enough to question the randomness. But over many shuffles, it's clear that it is consistently playing some artists considerably more than expected and others considerably less.

But I think you're right about the solution. My "least-played" approach works for me, but your "last played" is a good one as well. Wasn't aware of that capability. Thanks!

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