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979,140 Views ā¢ Mar 24, 2023 ā¢ Click to toggle off description
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Views : 979,140
Genre: Science & Technology
Date of upload: Mar 24, 2023 ^^
Rating : 4.979 (238/44,814 LTDR)
RYD date created : 2024-05-14T11:13:26.650385Z
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YouTube Comments - 2,665 Comments
Top Comments of this video!! :3
This technique is still a thing in digital recordings. In a "joint stereo" MP3 encoding, the sound is encoded as a mono channel and a stereo difference channel. The reason is that it compresses more efficiently and results in smaller files for the same quality.
2.2K |
Fun fact: I often accidently heard only the stereo difference: When the headphone jack is not plugged in all the way, and both channels have contact but not the ground, you hear only the differences between the audio channels. Happened a lot in the good old days with mp3 players
355 |
When you started discussing stereo difference channels using Audacity, it was very satisfying. I have a fun story about a radio station that did this by accident, causing me to make a curious detour on a job.
Back in 06, I was at university, and also working for the university's media department. They wanted to play the campus radio station over the ceiling speakers in the lobby of the student union, so we put a receiver in a closet and connected the signal. Only -- the ceiling speakers weren't in any kind of stereo configuration; the whole array was driven off the same mono signal, so we had to pass the radio station through a little downmixer. At first I didn't have the part with me, so I just shoved one channel through the speakers to test them, and then I went and got the downmixer to install.
When I did that, I found the audio almost totally went away.
I checked the wiring and I hadn't messed up; everything was connected the right way. The level indicator wasn't zero, though, so I went from the closet into the lobby with the volume turned up and it sounded like I was underwater. The signal was there, but coming out mud. I tried a different source signal, and it came out fine (after I almost blew out the speakers from nearly forgetting to reset the volume levels). That's when I had the thought, "oh crap, the radio station, they're broadcasting their stereo channels 180 degrees out of phase."
One of my roommates had a radio show and worked as a technician at the station so I told him about it. To prove what I was saying, I captured a segment of the station's live Internet stream, which I knew from my roommate was driven off the same mixer as the FM broadcast, and the software I used to capture it was Audacity. All I had to do was combine the left and right channels -- without having to invert one -- and play it back.
"I think you've got something wired backwards," I said. We went into the station the next morning and fixed it. They were using analog audio equipment, not digital mixers, and at some point the polarity of one channel had been reversed in the feed.
That is the first time in my life I got to fix something by reversing the polarity, and it did satisfy a good chunk of the childhood engineering dreams I had since watching ST:TNG at age 3.
1K |
Vinyl record trivia: Monty Python (back in the day) cut an album that had two sides on one side: Each 'side' was cut in one spiral grove right next to another spiral grove. Depending on how you set the needle down, you'd get one track or the other. They had no mention of this on the album notes, just left it for you to figure out. Of course, each track was half the length of a regular album side. Crazy!
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My hearing is degrading and I usually have captions turned on (and hearing aids). I just about lost it with the captions on the Audacity playback! š¤£
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Here I am, retired and in my 70s with a lifetime (well almost) in electronics and it never occurred to me to question how stereo sound works on a vinyl record. Thanks for the ātraining sessionā.
109 |
i've worked at a record store for 8 years now and the technology behind vinyl still blows my mind thank you for doing this
113 |
iām a mix engineer and sometimes when I master digital recordings i re-introduce a bit of crosstalk to taste because sometimes it makes the imaging sound a bit more grounded! so much of digital recording involves re-introducing imperfections that you just kinda had to live w in analog. Like saturation, for example. love that you played the stereo difference signal of the outro music lmao. cheers
42 |
Fun stuff. I'm old enough to remember the coolness of the original stereo records. But honestly, what really WOW'ed me was "quadrophonic" records. That could also be an interesting follow-on to this...
273 |
I never expected Alec to add papercraft to his list of tools to explain with but I am ALL for it!
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Loving the inverted credit music haha! Phase cancellation is essentially what weāre listening to. The difference between the sounds that isnāt cancelled. Love the video!
77 |
A tip for anyone doing restoration of stereo audio off records. Because dust and crud sits in the bottom of the groove, it proportionally affects the stereo difference signal more than the mono signal. Convert from LR to MS then do your de-clicking etc. on each separately. Be careful not to use anything that might affect the phase relationship between the two signals. Then convert back to LR after processing.
318 |
BTW, fantastic job on describing the audio in the captions! Many people never seem to get that captions are more than just what words are being said...
259 |
I'd be super interested in hearing you cover quadraphonic records.
206 |
Fun fact about the mono and āstereo differenceā signals (better known as mid and side): There is a drum micing technique built around this principle! If you take a cardioid mic, and put a bi-directional mic right next to it, but pointed perpendicular from the sound source, you can get stereo drums that collapse perfectly to mono. Simply add the two signals together in one channel, then subtract the bi-directional signal from the cardioid in the other, and you have stereo drums!
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That concept would also be used in FM radio broadcast. The combined channel is the main band while the difference channel is a side band. When the signal strength is weak the radio will swap to mono to retain quality.
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It's worth mentioning that vinyl stereo is in a way a bit more limited than stereo on another medium like tape or CD.
For example, there's a limit to how loud you can have a panned sound. If you have a really loud bass drum hit in just one of the channels, you risk launching the stylus out of the groove. One of the things I was told when it comes to dance music production is that, for vinyl mastering, you absolutely must not pan your kick drum or bassline. CD doesn't have this restriction.
220 |
My favorite part was the stereo - difference outro. š I love hearing things that you can't normally hear hidden in the stereo - difference channel.
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Your closed captions are just A++! Such a small detail that screams attention-to-detail! Love your content!
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@TechnologyConnections
1 year ago
A CLARIFICATION: My script is missing two important words in describing the stereo groove: "behaves like." When discussing stereo-difference signals, I declared that that's what's on the record - which is arguably true but only when you consider lateral and vertical stylus movements in isolation. The raw L&R channels are still encoded as purely diagonal groove movement, but the phase difference in the the cutting head's actuators ensures that those movements, when combined and equal to one another, only result in lateral motion. The cartridge also has its pickups wired with the same phase arrangement to ensure the L&R channels are in phase with one another when playing a mono record (or the virtual center of a stereo record). Is that a mono signal in the lateral motion with stereo-difference information in vertical motion? Well... you decide!
1.3K |