I am very non technical so please excuse my ignorance. I have a large music collection collected over the past 15 years with various file extensions. My latest difficulty has been in getting Roon arc to work with some of them and I have discovered that I can play files with AAC extensions I cannot play any of them on my Android device that have M4A extensions. Can I just manually rename the files from xxx.m4a to xxx.aac or do I need to get one of the many audio converter programs to do this? Thanks for any advice. I am always amazed that in our world of advanced technology, half of the things do not work with the other half because of business/money reasons.
AAC is the actual audio codec that was used to compress the audio, while m4a is just a file extension.
It causes confusion because most m4a files have AAC content, but they don’t have to, they can also have content that was created with a different codec. In this case, renaming them from .m4a to .aac won’t change that content.
The most likely cause for the failure to play them is exactly that, the m4a files contain content from a codec that is not supported by Roon. In this case you will need an audio converter to convert them.
Also see Audio Stream Format Not Supported here:
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Thank-you for that very clear explanation. If they have AAC content, but an m4a extension, will Roon still import them or does it need a .aac extension?
.m4a files that contain AAC or ALAC streams should play, is my understanding. It’s just that if it’s .m4a but contains something unsupported like MPEG-4 it won’t play.
You could open the files in QuickTime and it should tell you what the actual codec content is
The thing that got me going on this was that Roon Arc would report “corrupt media” on AAC files that Roon plays correctly on my PC. When I ripped these files from CD to MP3 files, Roon ARC worked fine.
Once I started looking into it on my pc, I noticed the “skipped files” and saw I have thousands of MP4 files that Roon itself did not import, even though it plays the ones with .aac extensions fine. So I think I will get a music converter and start converting my .m4 extensions to .aac - which should take care of the main Roon playing all my files. But for Roon arc it seems I have to stick to mp3.
I have around 800,000 tracks and am getting up there in years and do not want to spend the rest of my life glued to a screen converting things. I love Roon for many reasons but might have to see if there is anything that plays mp4s as well as mp3s.
I have m4a files playing fine on my Android, see …
… and here’s the file details …
Guess, you’ve got a different problem …
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Marin - thanks for sharing this. It certainly is confusing for someone not schooled in all the file formats and licensing agreements and the differences in the “Format” and the “extension” I thought even though aac formatting was supported by Roon, .m4a extensions are not - from the support website - and my experience seeing all the .m4a files in my "skipped’ folder. I get “corrupt media” on Roon Arc for every CD I rip in windows media player using aac with an m4a extension. I do not think there is any hope for me figuring ever figuring it out on my own and that I should just spend my time listening to the radio. 
Thanks for all your patience and information. I think you are exactly right. I have been ripping music to CDs for numbers of years using whatever pc, os and music programs I randomly have so my library is a mess of metadata, formats, extensions, etc. I think mentally I have come to the conclusion to use new technology as it was intended to be used - with all new, forward looking ways of listening to music, and not all the esoteric ways to listen to old things. Otherwise I will spend the rest of my life converting, renaming, sorting metadata, etc of my old stuff. If I want to listen to the old stuff I should just pop in a CD or put on a record. Thanks for all you help but I think it is hopeless!!
Why are you using that codec and container, anyways?
Do you have no other/better choice of format available?
Marin - I am an older guy and have been ripping files for many years using a variety of PCs as well as music software programs SW programs. I made the decision early on to keep all my music organized on a PC in windows file folders, organized as I like, as mp3s so I could find what I want. I now have over 800,000 legacy tracks. I keep these on an 8TB drive (in my windows folder file structure) in a Dell PC and run the Roon core on 1TB SSD c:drive. I find ROON to be a wonderful way to interface with and play the majority of these and present a user interface that is informative and educational. To answer your question I use Windows Media player for simplicity to rip files and then I move them to my own file structure and let Roon deal with them from there as a player - I have not found another player who does this so elegantly. I listen on a very low fi system to a variety of styles throughout the day. I admit that I am technologically challenged and would love to hear what you think might be a better way handle my situation. Is there any single solution out there that can organize the metadata and extensions of a library of this size, be used to rip new things and add to it and be used for listening to it? Although with CDs on the downturn maybe ripping isn’t the way things are going.
I’m an older guy myself.
Ripped CDs with iTunes to ALAC in m4a container back in the days.
Never used win media player.
Haven’t got 800,000 tracks to manage.
So I better back out of this, sorry to have intruded.
Maybe others are better versed in that sort of territory to give sound advice.
Roon is good for the listening and discovery part of your question.
I would NOT use windows media player for anything. My mother did this for a while until I got her using dBpoweramp (I went through a lot of files fixing what she had accumulated over the years)
I would recommend using dBpoweramp to rip and convert all your music to FLAC or ALAC. The format you want is really up to you but I have been using FLAC for a very long time and it works well for me. dBpoweramp also has a “batch converter” that would allow you to convert a lot of files with just a few click.
Marin - Thanks for the ALAC to m4A information! I appreciate you sharing your knowledge.
Bear - I used to use dbPoweramp and really liked it so I think this might be a solution to my current problem. I never encoded into FLAC because disk size (320mb!) used to be a concern, but now storage capability does not seem to be a limiting issue. I think my strategy will be to keep all my .mp3 formatted files and use dbPoweramp to convert the m4a extensions to .aac. It is my naive assumption that this will get rid of the bad stuff for Roon yet not manipulate the original encoding too much. On an ongoing basis I will use FLAC or ALAC for ripping and see how it works. Thanks for all the help!
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FLAC and ALAC are both lossless formats for audio.
FLAC may result in smaller files with the same quality as FLAC does have some form of internal compression in the codec.
I believe ALAC just strips away unused bits to result in a smaller file.
Neither are lossy like mp3 or AAC.
Thank-you FFK!
ALAC compression rate is comparable to FLAC but requires about four times as much CPU power to decode than FLAC does. (Not ideal for ARC battery life I suppose)
Kind of applies to both formats I guess…
FLAC compression can be set from 0 to 8. This will greatly change amount of cpu required to decode.
Well, it has the most effect for FLAC encoding time, less so for decoding, but anybody changing it away from the default 5 makes they own bed.
And of course a comparison of encoding/decoding time only makes sense when comparing the same actual compression, and ALAC seems to fare worse when comparing like for like
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