Hello,
i recently got the impression, that PlexAmp downloads tracks multiple times, if the same Track is present in a Playlist and in a Album, both set to downloa for offline use.
This impression originates just from watchin at the progress report on the downloads screen, say a Album and a Playlist only containing the same Album both seem to download. So my question is, if PlexAMP performs some kind of duplicate checking prior to downloading tracks?
Best Regards
Dominik
it does not because 1) it was much simpler not to and 2) it’s not a super common scenario for there to be a lot of overlap and 3) space is cheap.
Thank you for droping in @elan, but i guess this scenario might be more common than you assume.
Given that PlexAMP is advertised for the “Audiophile” and “Enthusiast” i expect that serveral of that user groupe maintain things like ratings for their songs. Now given you create a Playlist like “5 Star Ratings” it is near to certain, that the songs of your favourite albums are on that list.
What would you sync to your device? Right, the list of your favourite Songs and your favourite Albums. So there are duplicates already. Than you may also sync “Recently Played” because its highly likely that the songs your listend to yesterday, are a good choice for today too. This creates even more duplicates. Than you may already have different playlists for driving to work, cruising, runing etc… Again, more duplicates.
This does not only come with costs of device space, but also with costs in transfer/refresh-duration and not to mention calculation-time on the server to eventually convert tracks multiple times.
So, what are the costs of deduplication? As far as i understand, in Plex-Server tracks are identified by a “ratingKey” which is a integer. A naive inplementation of deduplication would be to keep a list of "ratingKey"s present on the device, and check against that prior to sync. This would be a simple integer-comparison with a maximum cost of O(n) and an average cost of O(n/2) for already present tracks for every new sync request. To reduce that list, you may even keep a list of "parentRatingKey"s, and check those first, which, on an aveage of 15 Tracks/ Album should reduce cost even further.
Concerning cheap storage, i would think, it would be more valuable for users to use that space for pictures and videos of their precious time with say their children, than for a offline cache for their music.
I am highly interested in the teams reasoning against this cenario and highly appreciate your work an Plex and PlexAMP!
I agree @elan with the previous poster. Space is not cheap, and the chance of duplicates very much depends on use which I believe to be high between ratings playlists, favourite albums, favourite playlists (including the previous 2 categories), recently played playlists, most played playlist, up and comers playlists and newly added tracks. In my own experience, I could easily have 3, 4 or 5 copies of the same track on my phone.
This is on top of the still baffling decision to only allow a maximum of 24 hours of music downloaded per playlist, which leads to multiple playlists being required to ensure that all the music I want to have on my phone, is definitely on my phone.
While I love Plex and Plexamp and admire the “keep it simple” attitude taken here, I consider it to be the wrong decision.
Sometimes this duplication problem also affects Plexamp caching system. I downloaded a playlist with some songs. Some minutes later i download an album with a song included in that playlist. Then i listen that album from Artist view. Plexamp stream the song included in playlist i downloaded some minutes ago instead playing from offline cache. If i download that album first this problem does not happen. Spotify mobile client and Finamp uses an unique identifier for each song to avoid duplicates
Noted.
That’s not true. There was a bug on iOS but it was fixed recently. We do have the same unique identifier system when “Prefer Downloaded Media” is on.
I had that issue at download that playlist before upgrade from 3.7.x to 3.8 and downloading the album after the upgrade. I did a clean reinstall, downloaded all albums included in playlist before downloading that and i hadn’t any issue. Tested on Android 11
Then perhaps you’re being fooled into thinking it’s streaming because it shows up on the web dashboard?
If not, we can’t really guess at what you’re seeing w/o a log.
This is a bummer. I like Plexamp, but will be unable to use it given my desire to sync playlists as well as individual albums. Space may be cheap on a laptop/desktop, but not on mobile.
Are things really going to overlap that much that a few 10s of MB will make a difference?
Yes. I have several large playlists for different purposes - exercise, car, my favorites, kids favorites, etc. Many of these overlap, even multiple times.
That’s besides the fact that (unless something changed recently - I had a particularly annoying failure in trusting Plexamp on a vacation trip once and discovered this), if I am without a data connection, I can only play what I’ve downloaded. In other words, if I sync a large playlist, I will be unable to search for individual songs or albums, I can only play the giant playlist. Conversely, if I only download albums, I will lose playlist capability.
I’m not trying to complain btw, I just really like Plexamp and would like to use it. I can accomplish what I need above with the regular Plex app 
Hi @elan I think you’re significantly underestimating the amount of overlap between playlists. 4 and 5 star rating for tracks (2 separate playlists because I can’t get both ratings in one playlist due to the 24 hour limit on playlist downloads in Plexamp), Artists I always want downloaded (unsurprisingly my favourite artists which tend to get higher ratings), Most Played tracks (influenced by what’s downloaded, my favourite tracks and highest rated), recently added albums, recently played tracks, favourite albums which I can’t search for when Plex is unavailable (or I don’t want to waste cellular data) so I need to make standalone playlists for each album.
All this is made worse by the fact the amount of music I can download on a single playlist is limited to 24 hours worth of music.
And this isn’t about how much music I can listen to in a day, it’s about having the right music available when I feel like it.
Ideally I could have one playlist I could sync to Plexamp which I could then search locally for the artist, track or album I fancy right now, but the arbitrary restriction on the amount of data I can download in a single Playlist and the fact that search doesn’t work without a connection to my plex server makes the only option available to download MANY, MANY playlists which currently comprise over 6000 tracks (From a library of over 20,000 tracks), and I have only rated about half of my music so far after moving from Apple’s music app, so it’s going to get worse.
This isn’t 10s of MB of wasted space, this is GB and GBs of wasted space. Of the 53GB of music I have downloaded, I suspect that somewhere between 20-40% is duplication e.g. 10-20GB. As I continue to rate my library, I expect the number of tracks downloaded to double.
I’m sorry if this is coming across as angry, i’m not angry, I’m passionate about my music and disappointed that the only way to ensure I have everything I want available at all times is such a compromise.
Have to agree with the previous posters–this is a really serious oversight. Tbh, I just took it for granted that the app must perform this check and not download duplicates, until I watched it closely as it was refreshing. Having refreshed my 4-star list, I expected the 5-star list to just perform the check and be done. But no, it’s re-downloading more than a Gig of music. Then I have playlists of favorite tracks from my top artists, so that’s another couple GB of duplicates. I’m just guessing, but I think the overall size of my Plexamp downloads would be cut by nearly 50% if there were duplicate checking.
This is a bummer. I’m planning on going on a trip and wanted all of my music available on my phone but it seems that plexamp may not be the right option for me as the offline usability is not that great. I think I’ll go back to MediaMonkey until there is a true offline mode.
That is not what Plexamp is designed for.
Thanks Elan, that’s the first time this has been mentioned even though many, many times people have said that they want to do just that.
All I’m aware of is that it’s a music specific client for Plex. I’ve seen people talking about wanting all of their music on Plexamp, I’ve said that too, but no-one’s told me the product isn’t for that.
So that was it designed for? (if read within context, this post may sound angry. it’s not, just frustrated)
I’ve covered this in a number of other forum threads, but the offline system in Plexamp was designed to keep a “reasonable” amount of music offline, but not entire music libraries. Instead, we recommend making use of the flexibility of the system to download smart playlists which “window” into content, stations, etc.
Please understand that what many people consider to be a reasonable amount of music to store on their device is entirely subjective. It’s clear that many believe it would be reasonable for them to store their entire collection. For me personally, my entire collection (nearly 1300 hours worth) would be unreasonable, and unnecessary. What WOULD be reasonable, though, would be all of my playlists and a great number of my favorite albums. That would consist of (as a guess) between 350 to maybe 500 hours of music. So I would have no issue with allocating the storage for this, but overlapping would definitely cause the required storage to jump considerably, and should therefore be addressed.
I’m a little miffed at how often I’ve seen you respond with “this is/was the easiest way to to deal with issue x, y, or z”
I’m not sure what you’re referring to, but engineering is a series of tradeoffs in general.
There’s one instance
Another (would not let me quote, but…) you said “capping it is obviously easiest 
there will always be someone who wants more”
Can you please address the main body of my comment. Thanks
