"Usually makes 320kbps files 2-10% smaller LOSSLESSLY"

That sounds useful... If it was still 2005...
I have 27 000 mp3 files (320kbps) - 177GB... ripped from CDs, so I'd save 8,5GB of space (on average, plus minus).
I'm actually re-ripping all my albums to FLAC (feels like a never ending job) - I'd rather have my music in lossless format than save peanuts of HDD space.

Didn't say it was huge gains.

Most of the music of 192kbps or higher i don't notice any issues with, so it's fine for me.

I didn't say you said it was huge gains. I just wanted to add something, not criticise what you said. I actually learned something new - I didn't know you could optimise mp3s without reencoding.

Whether you hear the difference between mp3 and lossless depends on a couple of things: bitrate, the original (type of) music, playback system, your hearing. People who say that there's no difference at all - usually, conveniently - don't mention these variables.
"there's no quality difference between mp3 and lossless!!!" (not mentioned: bitrate / I'm half deaf / I listen to dance/metal via my crappy laptop speakers).

I've ripped all my (+/- 1500) albums to 320 kbps mp3, starting in 2003. Back then, I didn't have the money to buy sufficient hard drive space for lossless. A few years ago, I started converting them again to FLAC (I don't know when I'll ever be finished). For some music, I don't hear the difference - but it's obvious for other music! (listening to good (monitor) speakers). Anyway, obvious or not - lossless is like a perfect backup.

I didn't know either til about 2 months ago when i stumbled across the tool. I'm looking for other tools that will do others, but not finding much.

True, the type of speakers or setup would make a difference. What was it, back 20 years ago i spoke with a guy who was talking about the technology, about how much you can compress the data down so it could be transferred via MP3 or other codec, but for the actual speakersystem you would have to turn it up so loud to be able to hear some of the details, the amount of data that is lost (but we generally don't notice).

Course he also spoke about how they tested speakers and stuff using bats and sonar to make sure the equipment was working...

OGG is probably a better format than MP3, as MP3 made certain assumptions and certain ranges that they drop for the compression (Or so i understand, though at a high enough bitrate it probably keeps it). OGG also makes it easy to do lossless as well compared to MP3.

If you wanted i could provide a script to convert the MP3 files, but re-reripping would ensure any loss of quality didn't happen.

I don't care about the format - I have no device that has issues with (any) format. There's just no way to turn mp3s into lossless without re-ripping the original CDs.

At home I play my music on my desktop PC (audioengine a5+ speakers). Not at home, on a smartphone with a 400GB SD card - FLAC is too big for that - but 320kbps is good enough considering the headphones and enviroment (bus).

Somewhere in the (near) future, I'll install my standalone CD player again, for whenever I feel like playing my music the old school way.

What MP3packer does, is not what I was talking about.
Essentially it just saves some space changing CBR MP3 files to VBR ones (constant to variable).

I've never been a fan of Variable Bit Rate. Players can have enough issues, without needing to deal with constantly changing bit rates. You are making them work hard etc for a miserable gain in space.

Maybe. And maybe not.

I remember back when i was converting some anime dvd's to AVI, and i was using DivX or XVid or some codec. And you know, there was a raining scene, and the scene looked TERRIBLE!, blockly and unviewable. Then i learned about 2 pass variable bitrate which i could pass through VirtualDub, where it does one pass, finds where the bitrate needs to be, and divvies up the bitrate so the raining scene looked good and others that didn't need all the space looked good too.

The biggest issue with VBR is that when you seek to a different part of the audio it isn't sure where the actual start there is. But if you are just playing it straight through it's generaly not an issue (Probably).

Not really comparable with audio, and the truth about what you are saying for video, is that the portion of the video that needed it, got a higher bit rate. You could have also improved the overall constant bit rate and achieved the same thing ... with obviously more space used, and with a video that space might be a significant increase.

You rarely gain much space when converting CBR audio to VBR, though of course that is playing time dependent, so I am talking an average length music track (3 to 5 mins) and not some 15 minute opus. VBR may have been a good option back when you needed every Kb you could get, but not really worth the bother nowadays, when even thumb drives are quite large. VBR takes longer to convert to and makes whatever player work harder, and some barely cope. And personally I see every audio file I create as a backup and I want the best form for that.

Depends on the audio. If you have raw audio of oh i don't know, a lobby going 24/7 for surveillance, you'll have dead quiet times (middle of the night) then you'll have busy portions. When analyzing the audio, 1/100th of the data could go to overnight when the feed was dead or white noise. For a 3 minute song where it's all active, yes you'll get very little difference in conversion, though if encoded that way to begin with you may get a bit better.

Considering i was targeting the usual size of 200Mb an episode (which is what a lo of them seem to be 200-400Mb), assuming 10Mb/min, That's about 1400kbps to work with; Though i think i was going 800kbps + 196kbps audio.. So if the quality of the video for the rain section that lasted say 2 minutes, needed a 10x quality in order to be good, Assuming i stay CBR and raise it to 8,000kbps and keep it CBR... At the cost it now takes up 1,160Mb in space for the episode... for a 640x480 episode of anime of 20-24minutes of time. Assuming i'm wrong and it only needed 5x, that's still 590Mb.