Downloaded a CD quality flac file and was listening to it but after a while my iPhone got extremely hot. Killed ARC and things went back to normal.
Not sure if this specific to the 14 Pro Max, iOS 16.0.1 or just the nature of local playback via ARC.
Probably because the iPhone is upsampling your CD quality file 48/24. This takes a lot of power. This should not be happening and needs to be fixed.
Same thing happening to my iPhone 11 pro. Running ARC always makes it hot, dim the screen consequently. This is something should be fixed.
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Hi @DrTone, @c2c2c2, @Sehune_Lee,
Thank you for the reports. Please note that the team has an open investigative ticket for this issue, so I wanted to check if you’ve experienced this again since your original posts.
Do your iPhones11 Pro or iPhone 14 Pro Max phones reliably heat up when using ARC, and if so, is there a specific file type or connectivity condition that seems to trigger this behavior?
We don’t want to assume upsampling is the only trigger here, so please let us know if you notice other conditions leading to the same behavior, and we’ll promptly pull diagnostics.
I haven’t tried it since. FWIW, I was playing back a 16/44.1 FLAC file.
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I wanted to give you an overview of my testing of Roon ARC and the issues related to the load it places on the iPhone – in my case, an iPhone 12 Pro.
First, in broad terms, the problem is that Roon ARC places a ridiculous amount of load on the phone as compared to other applications that are performing an identical function. For this posting, I am going to limit my feedback to files downloaded from the phone and then played from the local copy – versus streamed. Streaming has its own set of issues, but for clarity I am focusing on downloaded files.
The load on the phone has been assessed by the temperature of the phone (very very hot) and the amount of time the phone can play from a full charge until the battery is exhausted – less than 25% of the time versus other applications. I have compared this to several other applications that do a similar function – downloading a Redbook or above quality file to the local device and then performing playback. No application is as resource intensive as Roon ARC.
My library files are ~50% Redbook (44/16) and ~50% high resolution formats ranging from DSD/DXD to 192/24 and down. They are all in FLAC or DSF format. In the case of my library, when I’ve downloaded a file, Roon ARC will ALWAYS need to resample the file as none of these are in 48/24 which is what the iPhone wants to play. I don’t know if playing a FLAC file versus another lossless format makes a difference.
The inability to download a file in 48/24 for playback using the iPhone’s playback mechanism is one source of the load. I notice extended usage times and slightly lower temperatures when I am playing a file which I downloaded into Roon ARC at 48/24. (As a work around, I’ve created a full duplicate copy of my library in which all files (>10K Albums! – 82 hours of processing time on 20 cores! multiple TB of space!) have been resampled to 48/24 and I select that version for download.)
I have observed other cases where Roon ARC uses comparatively high amounts of power to perform functions which are much more efficient on other apps. I presume this is a collection of multiple small issues rather than a single big one – if this is the case, it’s just application tuning that is needed.
Until then, please allow phone users to choose to download a version of their music file in the native sample rate/bit depth of the phone. This will be a big step in resolving the problem.
This is also happening on my Samsung Galaxy S20. Is there way to prevent it from getting so hot? I also tried pre-downloading and listening in offline mode, but rhe phone gets eaqually hot after a while.
Hi @Chrissi,
Thank you for the report. We’ll keep your topic regarding the Galaxy phone separate rather than merge these threads for now, as the team is tracking this issue independently by operating system.
iOS reports we will begin to merge into this thread, as we have several reports with iPhone 11 Pro and iPhone 14 Pro Max.
At this time, the team is investigating the issue internally to try pin down triggering conditions. We’re not assuming it’s a result of normal or even extreme operating conditions on ARC or the phone. Transcoding won’t cause a hot phone in normal conditions, even with high-quality file types; neither should connectivity conditions.
We’re particularly interested in reports with downloaded, offline mode, and ARC playback using connected endpoints (like USB DACs).
Hi @c2c2c2,
Thank you again for your diligence and for the precision of your feedback.
Having investigated diagnostics, we’re seeing strong evidence that the size of the library is affecting Roon ARC’s performance. A library of 300k+ tracks, with 50% of them being high-quality DSD files, is unfortunately on the sunset end of the bell curve for database size that will function with any mobile sync setup.
Simply put, due to the size and file quality breakdown of your library, your Roon database may be too big to use reliably with ARC. In order to support operation with poor or limited connectivity, Roon needs to synchronize information about your music library onto your mobile device. While the data synchronized is much more compact than what is stored in the Roon Core, libraries above a certain size will naturally be too big for a mobile device.
Aside from limitations in device performance, there are also restrictions on resource usage imposed by Apple and Google which make this scale of data transfer, synchronization, and storage impractical within a mobile app.
There’s no hard barrier, but the team finds a natural limitation starts to assert itself in the range of 300-600k tracks. Of course, this depends hugely on the phone and the file qualities of the tracks. 400k low-quality files might still work; 600k large DSD files very likely won’t sync at all.
Keep in mind, however, that this might be fully independent of your report of a hot phone during downloading. There is memory pressure evident in logs during downloading, but there’s no direct evidence it’s responsible for the heat. It may be you’re encountering memory pressure in addition to the issue the team is investigating above, so we are by no means dismissing your useful insight or discontinuing further deep investigation into your reports.
Being the thread starter I should report that my library is about 159,000 tracks of which maybe 5% are HD PCM or DSD.
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Hey @DrTone,
It’s unlikely your library size is causing the issue, or @c2c2c2’s for that matter. At the risk of addressing two issues in one thread, I wanted to respond generally to the overview of performance in ARC provided above in post #7.
Similarly, even upsampling from CD Quality to 48/24 quality for system output is not causing overload on the phone, despite the common assumption that it would. Upsampling or transcoding alone are not the culprit, as we’ve deeply and consistently tested these mechanisms on these devices and operating systems both prior to and in the context of these hot phone reports. This issue very likely results from several processes in ARC overlapping in ways they shouldn’t, triggered by certain conditions.
The team has escalated and will be providing updates in this thread shortly, as well as in the thread @Chrissi has begun for Android users over here: Arc heating up my Samsung Galaxy S20
Thank you all again and I hope that this problem isn’t overly interfering with ARC. We’ll have more information soon.
XS Max here. Do you expect the phone to get hot while downloading files for offline use? I noticed this last night after downloading around 124 tracks. But I never noticed it before the last update when I downloaded album after album.
A little more data for you. Noticed the phone getting hot yesterday while using Arc (no downloads, just streaming), and the interface froze (music played fine) for a moment and then resumed, scrolled some more and it froze again. Happened both with wifi and 4G. Shutting down the app and starting again didn’t help, but restarting the whole phone did and now it’s working fine again (as it has since launch).
iPhone 13 running iOS 16.
Roon runs on a NUC10, 16GB RAM and SSD’s, 250k files (flac, alac, mp3)
Edit: Now it freezes up and getting hot again. Tried scrolling through the list of albums, no music playing.
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Hi everyone,
We’re continuing to make incremental progress in pinning this down. If the issue is persisting still on the latest build released this month - and particularly if it’s preventing everyday use of ARC - then please report here and we will do our best to provide a workaround in the interim. Thank you again for your patience.
Note that this release does not contain a fix for the overheating issue, but does include a constellation of fixes that may improve performance and help relieve symptoms overall.
Whatever you guys did seems to have fixed my issues at least. Been listening on the commute to the office and at the office (about 8 hours total) with no extreme heat or freezing. 
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Adding to this my 2020 SE gets very very hot when downloading and the app gets very slow and unresponsive, it does also use more battery than any other app. Not noticed it get overly hot whilst playing but then I use BT headset which doesn’t require it to resample all the time and on cellular I am on compressed feed so again resampling done on the core.
Xiaomi mi10 with custom rom. Its a top performance phone.
Roon core via windows with +300k flac files. 1tb up/dw network.
Issues are the same of users on this thread, app freezes the phone, consuming battery as hell.
Hope you fix this issue.
I have issues on the 14 Pro Max when downloading a large playlist (~10K tracks)
The phone gradually gets very hot and drains the battery (if I keep it on MagSafe then it drains faster than it can charge) It also crashes after a few hundred tracks. The crash starts with the screen flickering and glitching a lot, then the app crashes after a while.
Downloading a play list of this size takes a long time as it will crash many times.
@connor ,
Thank you for the reply, I do believe this is conflating two issues. Memory/resource pressure during sync/download and resource pressure during playback of downloaded files - say perhaps in off-line mode.
To address the issue of the phone overheating with downloaded files that are not in 48/24, I’ve had to double the size of my library by creating 48/24 versions of all my albums which I can then download to Roon ARC.
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