Regarding the 5.1 mix - I’ve only reviewed one episode (S01E02) - but if that’s consistent with the rest of the series I can say the following:
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I believe the 5.1 mix is the results of taking the stereo “music and effects” tracks, and running it through a Dolby surround decoder to get Left, Right, Surround Left, Surround Right and a low passed LFE channel - the mono dialog track is used to populate the center channel. My evidence for this is:
– Zero dialogue leakage to left, right, surround, or LFE channels
– Surround and LFE channel activity correlates pretty much 100% with activity in the left and right channels
— Checkout the dialogue heavy section between 02:14 and 03:48 (Giles spins a globe and spouts exposition), no LFE, no surround.
– Seems they’d likely have a M&E/Dialogue split so they could do other language dubs. -
This means a mixdown should be transparent-ish (see below images)
– A downmix of the 5.1 streaming track I made using ffmpeg looks pretty similar to the original soundtrack, there might be some minor equalization differences - but notice the ~15khz CRT whine in the spectrogram particularly at ~16 minutes present in both it looks to be identical (seems to be coming from the dialogue track)
– There is a question of the relative phase of the surround channels to ensure correct Dolby Surround compatibility in the downmix - would need to check that
Assuming this holds, it should mean that the streaming soundtrack can be downmixed (with the right ffmpeg command) to produce something very very close to the broadcast stereo soundtrack at much higher quality than any actual recording of the original broadcasts we happen to have copies of.
5.1 Streaming mix
DVD Audio 2.0
Streaming mix downmixed to 2.0 in ffmpeg
