The original setting features either a 2k or a 4k video feed and cristal clear audio. Here are some example stats of what the stream packs in for you:
Name: Original also HQ38
aka: 4k or 4096p or 2k, 2048p
Container: MP4
Video Codec: H.264(mpeg4 part 10)
Resolution: 4k - 4096x2304 (~xxxx kbps) or 2k - 2048x1152 (min. 1570 kbps)
Aspect Ratio: 16:9
Audio Codec: AAC 151+ kbps VBR, 44.1kHz stereo
So far I only saw 2 channel audio feeds, what is actually fine with me, because I mainly feed the earphones only. The rest of the youtube codecs and how to record videos and extract audio is described here.
(interesting: transcoding with lame.exe delivers catastrophic results for the first 10s)