4K Video Downloader's quality level : real download or upsampling ?

[Captain'Flam]

Hi !
I'm using 4K Video Downloader to download mp3 extracted from YouTube videos, and I wonder how it can offer so many bitrates...
On the extraction dialog box, I can chose between :

- Original quality
- High quality      320k
- High quality      256k
- Normal quality    128k  (same size as "original")
- Low quality       96k
                               ...and so on...

So I wonder if YouTube actually offers all these bitrates, or if 4K Video Downloader downloads the "original quality" and then re-samples it to the selected bitrate.
--> If it re-samples, does it mean (as I suppose) that it's useless to download better quality than "original" ?


Thanx in advance !

[badyu17]

I don't know if Youtube offers mp3 as audio codec today (maybe for very old videos?) but nowadays I only see AAC-LC and Opus for audio codecs when I list available formats with youtube-dl. So your program is probably converting to mp3.

[Captain'Flam]

Thank you for the answer+trick !
I downloaded and tried youtube-dl, and I get this :

format code  extension  resolution note
249          webm       audio only DASH audio   63k , opus @ 50k, 2.06MiB
250          webm       audio only DASH audio   82k , opus @ 70k, 2.74MiB
140          m4a        audio only DASH audio  128k , m4a_dash container, mp4a.40.2@128k, 5.20MiB
171          webm       audio only DASH audio  153k , vorbis@128k, 5.16MiB
251          webm       audio only DASH audio  156k , opus @160k, 5.41MiB
17           3gp        176x144    small   36k , mp4v.20.3, mp4a.40.2@ 24k (22050Hz), 1.47MiB
36           3gp        320x180    small   53k , mp4v.20.3, mp4a.40.2 (22050Hz), 2.19MiB
18           mp4        640x360    medium  149k , avc1.42001E, mp4a.40.2@ 96k (44100Hz), 6.10MiB (best)

(I omitted the "video only" formats)
I understand that my program convert audio to mp3.
So my question is now : which format is less destructive ?
I see "best" after "mp4a.40.2@ 96k", but 96k sounds more destructive than "opus @160k"...
And which mp3 bitrate is enough to contain it ?
I have chosen 320k, but it may be too much in regard to the 160k of vorbis...
Maybe 256k is enough to save the original quality ?

[badyu17]

Yeah, I forgot about Vorbis. Opus for Dash audio should be good enough, it's an awesome codec I hear.