opus - Jun 2018 - Is this the best method to keep audio quality when converting MP3 to opus?

Hello, I have a large collection of audio files contains music in mp3
format, due to need to free space of hard disk, I need to reduce their
size.

It seems opus is the best format for this purpose, in order to have the
quality of original mp3 files, currently I use ffmpeg command to
convert them to FLAC and then use opusenc, the official opus encoder,
to convert FLAC files to opus.

By using one standard and good quality headphone, My ears don't notice
any difference between original mp3 files versus new opus files.

1. Is this the best method to keep audio quality when converting lossy
audio to another lossy audio?

2. Is there any quailty loss in this method? if yes, is it noticeable?
how much is it?

THANKS FOR HELP

On Jun 01 13:46:11, farhadbenyamin at yahoo.com wrote:
> Hello, I have a large collection
How large?
> of audio files contains music in mp3
> format, due to need to free space of hard disk, I need to reduce their
> size.
You most probably don't. Buy yourself a bigger disk,
it's dirt cheap nowadays.

> It seems opus is the best format for this purpose, in order to have the
> quality of original mp3 files, currently I use ffmpeg command to
> convert them to FLAC and then use opusenc, the official opus encoder,
> to convert FLAC files to opus.
You will spend a lot of CPU time doing that,
depending on how large your collection is.
> By using one standard and good quality headphone, My ears don't notice
> any difference between original mp3 files versus new opus files.
> 
> 1. Is this the best method to keep audio quality when converting lossy
> audio to another lossy audio?
Converting from one lossy format to another is a bad idea in general.
> 2. Is there any quailty loss in this method?
They are both lossy formats, so yes, there is a loss.
> if yes, is it noticeable? how much is it?
It depends.

	Jan