[Greenears]

Thanks for all the responses. Note the real archive will be lossless FLAC.  All the tracks will be batch converted to a single lossy format.  So there will be two copies of each track.  Candidates are MP3 320, MP3 256 or AAC 256 a distant third.  It would be nice if they all ABX against lossless at least for 95%+ of material.  But the lossy format playability is key.  Compression is not such an issue anything in the 250-300 range is fine storage has become cheap.
 
One of the main reasons for the batch conversion is that Apple doesn't support FLAC.  And I'm not willing to archive in a proprietary format.  Beyond that a bit of compression is nice for the tiny portables but within 2 years it will be moot lossless will be enough compression.

 

[bigshot]

I did extensive A/Bing of various lossy formats and the most efficient was AAC, which became transparent at 256. MP3 LAME became transparent at 320, resulting in a little bigger file. I found a track that gave Frau 320 difficulty, but for 99% of cases, it would be fine. If you use AAC, make sure to use VBR. It can't hurt, but can only help.
 
By the way, neither ALAC nor AAC are proprietary formats. They are both open source and have wide support. If you have a Mac and an iPhone and use iTunes, there is no reason to use FLAC or MP3.

 

[Greenears]

  I did extensive A/Bing of various lossy formats and the most efficient was AAC, which became transparent at 256. MP3 LAME became transparent at 320, resulting in a little bigger file. I found a track that gave Frau 320 difficulty, but for 99% of cases, it would be fine. If you use AAC, make sure to use VBR. It can't hurt, but can only help.
 
By the way, neither ALAC nor AAC are proprietary formats. They are both open source and have wide support. If you have a Mac and an iPhone and use iTunes, there is no reason to use FLAC or MP3.

Thanks @bigshot!
 
That saves me a bunch of testing, I will trust your results.  I'll probably spend 10 minutes doing an ABX on the final choice just because it's easy but I'm not going to spend a lot of time.  Based on this I'll skip 256 MP3 and the most likely is 320 MP3 LAME vs AAC 256 VBR second choice.
 
The AAC is partly irrational - the current library has every format and encoder imaginable in a big jumble.  I still today run into non-playable tracks on both Windows and Android.  You install some random plugin and it goes away, only to return at some point..  The non-playable track is NEVER an MP3, ever, that I recall.  Maybe 320 will trip some up but I doubt it.  With some work I could figure out the real cause, but I only want to do this once.  Bit rate is no longer an issue - it might have been a while back.  128G storage solved that problem

 

[nanaholic]

   
Youtube and many streaming services use AAC. It's pretty standard. Even car stereos play it now.

 
No doubt.  You won't have any issues when it comes to PC related equipment and it's safe to say that any consumer electronic you buy now that is made within the last two to three years will play AAC without you needing to read the "supported file format" list.  The issue is what type of equipment you have in that bag of "exotic stuff".  I would not be certain that a head unit from say, 7 years ago, which claims to be "mp3 compatible" or "plays file from a USB stick" would play AAC, yet those things are still circulating in the market and quite widely.  In that sense, mp3 is still the way to go for maximum compatibility unless you are absolutely sure the type of equipment you have or will be buying.

 

[Greenears]

@nanaholic  It's all over the device map.  For instance a Samsung HDTV has a DLNA player in it which seems to have very limited choices.  It's not that important I use it rarely for this, but if I choose to, I never want to see that dreaded "unplayable file" message ever again.

 

[bigshot]

That's why I always make sure my players are swiss army knives. My disk player is a region free modded Oppo BDP103D. I can plug just about anything into it and it plays.