[HN Gopher] Smoother sailing: Studying audio imperfections in St...
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Smoother sailing: Studying audio imperfections in Steamboat Willie
Author : firloop
Score : 167 points
Date : 2024-01-25 16:05 UTC (1 days ago)
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(TXT) w3m dump (www.windytan.com)
| h2odragon wrote:
| also: https://hackaday.com/2024/01/24/steamboat-willie-never-
| sound...
| NoZebra120vClip wrote:
| The film has been played on endless repeat, with "original
| sound", since the 1970s, at Disneyland's Main Street Cinema.
| https://en.wikipedia.org/wiki/Main_Street_Cinema
|
| It would be interesting to see if anyone has made remarks on the
| sound quality and whether the flutter has been noticeable over
| the past 50+ years.
| djmips wrote:
| It certainly has been noticeable. It just gets mentally filed
| under 'old timey' sound.
| m463 wrote:
| and people just must have been more frenetic in old-time
| movies, moving faster and more jerkily
|
| not a hand-cranked/fps mismatch
|
| I kind of wonder if the cameramen cranked slower sometimes to
| save film
| thrdbndndn wrote:
| I never understand why playing at wrong FPS for these old-
| time footage is a thing. It was so obviously wrong.
|
| (By that I meant in "professional" settings, like a
| commercial release. You see people stretching 4:3 videos to
| 16:9 all the time on YouTube, Tiktok etc. but at least
| Warner Bros. isn't going to do that. However the FPS
| incorrectness used to be prevalent even in the industry.)
| ok_dad wrote:
| How do you suggest taking 24 FPS and turning it to 29.976
| NTSC? A lot of times, they would just convert it 1:1, so
| the 24 frames would go by in a 24/~30th of a second, so
| it looked faster. Further, a lot of old, old film was
| actually meant to be played at slower FPSes than 24, I
| think 8mm was like 18 FPS.
|
| Today, we do key-framing and other tricks to make
| transfers from different FPSes easy and imperceptible
| (plus with digital stuff we can playback at any FPS), but
| back in the 80's and 90's the tech was a lot less
| advanced to turn a film image into an analog or digital
| format, and in previous decades you didn't even have
| analog or digital, you just had to use 1:1 frame
| transfers to get onto a larger or smaller film format.
| sgtnoodle wrote:
| 24FPS is typically converted to 60Hz using 3:2 pulldown.
| Show one frame for 3 fields, then the next frame for 2
| fields, then 3, then 2, etc.
| thrdbndndn wrote:
| > How do you suggest taking 24 FPS and turning it to
| 29.976 NTSC?
|
| 3:2 pulldown, which has been done for decades.
|
| You can also just duplicate frames (un-evenly). It will
| introduce jitter but most of people aren't very sensitive
| to that, and it's better than playing at wrong speed.
| charcircuit wrote:
| As professionals they should be shooting at 29.976 fps if
| that is the fps the end product is supposed to be.
| Messing up and using the wrong framerate when recording
| is for amateurs.
| rjmunro wrote:
| The end product is supposed to be 24fps for a cinema. But
| then a TV company wants to show the already-existing
| film. It needs to be solved.
|
| In PAL countries, 24fps movies are often played a bit
| fast at 25fps on TV so that each frame fits nicely in the
| 50hz signal. It's not a "Squeeze more adverts in" thing,
| it's the best way to show the film, otherwise you'd have
| to introduce an extra frame every second, which would
| look jarring.
| callalex wrote:
| Well, tv stations these days speed up the playback of
| older shows by a few percent so they can fit more
| commercials in than the original creator provided time
| for. I'm so glad I haven't payed for cable in a very long
| time.
| toast0 wrote:
| If you're lucky they speed up the playback. If you're
| not, they cut to commercial on a schedule, damn the
| content. Doesn't matter if you miss the punchline of the
| joke that was being setup this whole time.
|
| Of course, it's worse with online tv with ad breaks. The
| online ads cut in 2-5 seconds before or after the program
| break, so it interrupts the content, and if you skip back
| to try it again, they play another ad, also inserted
| incorrectly. To make it even worse, the ads are usually
| at a different framerate and resolution from the content,
| so you get a new resync and a new hdcp handshake, so
| there goes another few seconds of content; unless you set
| your player to fixed resolution and framerate which isn't
| ideal.
|
| I'm in prime circumstances to be a couch potato in front
| of the tv, but it's so damn frustrating, it's not worth
| it. You can't even channel surf, because tuning a new
| channel takes too long, so you've got to plan your
| changes.
| toast0 wrote:
| > I never understand why playing at wrong FPS for these
| old-time footage is a thing. It was so obviously wrong.
|
| Old-time footage isn't always at 24 fps, but once the
| film industry standardized hard on 24 fps, not standard
| film becomes very hard to use correctly, even in a
| projection environment --- projectors were engineered
| around 24 fps all the time, and likely can't be adjusted.
|
| Tv of course was fixed at 60 fields per second (or close
| enough) or 50 in Europe. Even today, a US market tv is
| going to do terrible things with a 50 fps signal
| (although I gather EU market tvs work at 50 and 60 and
| probably 24). If your old-time film was shot at 22.3 fps,
| you don't have good options to show it, except on a
| computer with a VRR display, and even then, I don't know
| if the whole chain will actually be fine with it. Options
| are: pretend it is 24 fps and it plays a bit fast and you
| can use your 24fps pipeline; show some frames twice and
| have nasty judder; interpolate 24 fps from the data you
| have which is kind of terrible and only recently a real
| option.
| thrdbndndn wrote:
| Off topic, but what's the difference between the term
| jitter and judder?
|
| I've tried to google it multiple times, but every time, I
| can only find various forum posts which are all over the
| place (if not straight up contradict to each other).
| tetris11 wrote:
| From context I would guess that judder is a global effect
| (e.g. when the film pauses and then suddenly jerks
| forward playing), and that jitter is more local (e.g. to
| do with the movements of the actual characters on screen
| moving with sudden velocity)
| keithwinstein wrote:
| My understanding is that jitter refers to essentially
| stochastic variation of an ideally isochronous/periodic
| process or signal. You might say "the event is supposed
| to occur exactly every 1 second; in practice we observed
| jitter of +/- 50 milliseconds," referring to the RMS
| (1-standard-deviation estimate) of a sample of inter-
| event durations. Wikipedia has a nice article:
| https://en.wikipedia.org/wiki/Jitter
|
| In the context of video, I think the most common use of
| "judder" is about the deterministic and periodic
| variation in timing that occurs when content of one frame
| rate is shown on a different-rate display. The most
| common situation is a "3:2 pulldown," where 24 frame-per-
| second film content is adapted to a 60 field-per-second
| or frame-per-second video signal. This is done by
| repeating one film frame for 3 video fields/frames (so
| 3/60 seconds), and then the next film frame for 2 video
| fields/frames, then the next one for 3, then 2, then 3,
| then 2, etc. (2/5 = 24/60 so it works out on average.)
| That repeating variation in frame duration or number of
| repetitions is seen as "judder." With a cinema projector
| or recent TV, you don't have this; the frames are shown
| 1/24 s apart and with an equal number of flashes each.
| But on an older 60 Hz TV, you'll have judder.
|
| (I've also seen "judder" occasionally used to refer to
| the stuttery motion that comes from showing 24 fps
| content on a sample-and-hold display, like an OLED
| [without black-frame insertion] or a "good" LCD that just
| shows each frame with constant brightness for the entire
| 1/24 s and then almost-instantly switches to the next
| frame. But I don't think this is the correct usage.)
| toast0 wrote:
| Adding on, jitter is something you can address with
| better precision (various mechanical and later electronic
| means were devised to ensure a precise time between
| frames during recording and projection to reduce the
| jitter between frames in a film) or in modern times,
| larger buffers (if you're streaming video and packet
| delays vary by 50 ms, a small buffer will allow for even
| playback). Jitter buffers improve perceived quality at
| the expense of delay and memory use, but for recorded
| video and audio, delay isn't a big deal.
|
| On the other hand, judder is often due to a limitation of
| the system. Fixed frequency displays can't display off
| frequency content without compromises. And TV
| broadcasting was tied to fixed frequency displays. NTSC
| had no hope of 24fps support, sending two fields per
| frame at 48Hz or three fields per frame at 72Hz would
| both be way too far from the spec frequency of 60 Hz. I
| wonder if PAL@48Hz could have worked though --- 4% off
| spec is a lot, but also not that much.
|
| And bringing it back to old time film that's not at 24
| fps, that's definitely more hopeless.
|
| ATSC and I presume DVB can broadcast content as 24fps,
| and the decoder will do the 3:2 pulldown as needed, but
| variable rate displays can show 24 fps (it's also usually
| not too hard to detect and invert 3:2 pulldown, at the
| cost of adding a few frames of delay). I don't think
| modern broadcasting does better for a 22fps old-timey
| film than analog broadcasting did though; it's still not
| something the system was built for, and you're still
| going to have off speed playback or a pattern of some
| frames shown more times than others (which is my
| essential definition of judder)
| WalterBright wrote:
| The way movies used to be shown on TV was the movie was
| projected on a screen and the TV camera was pointed at
| the screen. The "interpolation" was simply the analog
| aspect of the TV camera tube.
|
| Low tech, simple, and effective.
|
| Some of my old family movies were converted to VHS that
| way.
| pavlov wrote:
| Btw, the industry term for transferring film to video is
| telecine:
|
| https://en.wikipedia.org/wiki/Telecine
|
| And going the other way, before the introduction of
| videotape, the only way to store TV programs was to use a
| kinescope to produce a film recording of the broadcast:
|
| https://en.wikipedia.org/wiki/Kinescope
| actionfromafar wrote:
| Wow, the tech was really intricate! 1
|
| It could invert negative film to positive, and it could
| color correct scene by scene by looking at correction
| codes or counting frame numbers, then applying the
| correct color correction.
|
| Later, broadcast TV started using flying spot scanners
| instead of just a video camera in front of a film
| projector. 2
|
| 1: https://en.wikipedia.org/wiki/Film_chain
|
| 2: https://en.wikipedia.org/wiki/Flying-spot_scanner
| babypuncher wrote:
| Modern TVs in any market will take 24 (23.976) hz, 50 hz,
| and 60 (59.94) hz. It's been pretty common to support all
| common refresh rates since displays went all-digital.
|
| The vast majority of midrange and better TVs can also
| spot 24 fps content being sent in a 60 hz signal and
| render it properly.
|
| Most TVs however will not look good with 50 fps content
| in a 60 hz signal and you will want to set your output
| device to adjust its refresh rate based on the frame rate
| of the content being played. Set top streaming boxes
| actually worth using have this option, but it is usually
| disabled by default.
| sgtnoodle wrote:
| If they cranked slower, maybe the film would overheat and
| burn from the lamp?
| madaxe_again wrote:
| Undercranking was generally used for dramatic effect, but I
| definitely have read about it being used to allow longer
| takes with a fixed film reel length - if you undercrank by
| 10%, you get 10% more time before you have to stop and
| reload.
| deredede wrote:
| It's even better due to the way percentages work - if you
| undercrank by 10% you get a bit over 11% more time (after
| 100% of the original time, you still have 10% of the reel
| left, but you keep undercranking, so by the end of the
| 10% extra time, you still have 1% of the reel left,
| etc.).
| WalterBright wrote:
| If a flywheel was used, the erratic nature of hand cranking
| would be smoothed out. I bet a governor system could be
| devised to make the speed correct.
| weinzierl wrote:
| _" filed under 'old timey' sound"_
|
| A little flutter was an unavoidable part of our audio for a
| very long time.
|
| I think producers sometimes add a little flutter even to
| modern music productions to make them sound less digital. At
| least that is my assumption from the number plugins that are
| available for that purpose and from the obsession producers
| and mixing engineers have with vintage tape machines.
| Onavo wrote:
| Neural upscaling would make it even better
| bagful wrote:
| In what sense? Higher resolution formats provide more true-to-
| life fidelity, but that's only more true-to-nonsense when the
| additional information is produced from extrapolation.
| thsksbd wrote:
| "This is an experiment [...] soundtrack was being read in the
| same way as the picture is - stopped 24 times per second? Would
| this be the ultimate flutter distortion?"
|
| That bothered me like crazy - how did they scan the audio whilst
| the frame was physically stopped? Then I realized how it was
| done: the soundtrack of frame A is stored in frame B, where frame
| B is far enough away that it has constant velocity.
| postmodest wrote:
| "Technology Connections Did It"
| https://m.youtube.com/watch?v=tg--L9TKL0I
| WalterBright wrote:
| > Then I realized how it was done
|
| Oh, I love ingenious solutions like that!
| thsksbd wrote:
| Aint it neat?
| stavros wrote:
| How does it have constant velocity? Is there a physical
| "buffer" for the stopped frame (ie slack in the reel)?
| Otherwise you can't stop one part of the reel while the other
| is still traveling.
| HPsquared wrote:
| There must be some "slack", the entire reel isn't going to
| stop and start 24 times a second.
| thsksbd wrote:
| Short:
|
| There _is_ a buffer!
|
| Long:
|
| So the frame being projected has to stop. Otherwise you'll
| get blurring unless your shutter is very fast, but then you'd
| burn out the film from the intensity of the light.
|
| The film is stopped.
|
| But, of course, you cant start-stop a 15 lb spinning reel 24
| times a second millions -> itll all fall apart.
|
| So the feed is a simple rotation at constant velocity
| (linear? Angular?). Then a piece of film ten to twenty (?)
| frames long gets put into a buffer (an empty box) and a
| mechanism akin to a sowing machine single steps through each
| individual frame.
|
| Now the stepping mechanism only has to start-stop ten frames
| worth of film, a negligible amount of mass compared to the
| mechanism itself and the projector can last a long time of
| heavy use with simple maintenance.
|
| Aint it neat?
| stavros wrote:
| That _is_ pretty neat, is it on both sides of the lens
| (entry and exit)? The synchronisation mechanism between all
| these things also sounds very interesting.
| thsksbd wrote:
| I dunno! I know nothing about projectors except what I
| dug out when the sound issue started bothering me. I
| imagine the buffer on the exit is just slack.
|
| The sync though is actually pretty easy, at least
| compared to computers and electronics - shafts and gears
| ensure synchronization with little effort (or you'd brake
| a shaft!)
| stavros wrote:
| But you'd need very tight tolerances to do it over
| thousands of revolutions (or you'd cut the film reel!).
| wiml wrote:
| Yes, if you look at a simple projector you can see it:
| there's a little half-loop of film before and after the
| shutter/lens assembly and you can see it vibrate as it
| buffers between the intermittent motion at the shutter and
| the smooth motion in the rest of the film path.
| derbOac wrote:
| I've often wondered, if there are multiple different prints of an
| older film available, they could be averaged or something using
| modern ML or computational statistics. I get the sense that
| "unsupervised" methods are underutilized a bit in film and audio
| restoration but I know next to nothing about this area.
| morsch wrote:
| Yeah, there are tools that do this. I know nothing about this
| stuff, but a recent Tech Tangents video had him combining
| multiple degraded prints of Contact. It's the final segment and
| the tool is called Id-disc-stacker. You need a lot of time,
| space and processing power.
|
| https://youtu.be/RduEpIiG0O0?si=uurvcfzVoOkf3zSW
| saberdancer wrote:
| I really liked the bit about first rule of government
| spending.
| enriquto wrote:
| I've seen this done for vinyl discs. You play several copies of
| the same old disc. The noise defects appear in different
| places, and can be easily removed by merging the aligned the
| tracks. Even with just two discs, the output result is
| spectacular.
| Solvency wrote:
| What software?
| enriquto wrote:
| It was a project by some signal processing students in my
| lab. As far as I know, they didn't get to publish anything
| besides writing a technical report; and the code was a
| matlab thing that just ran on the computer of one of
| them... But their presentation was excellent! They brought
| their vinyls, the turntable, and did a live demo of the
| whole thing running.
| Solvency wrote:
| Weird, why not sell it, or at least open source it? I
| imagine thousands of people would use it.
| modeless wrote:
| I've noticed a lot of jitter in the video, even in "stabilized"
| versions. It seems like there was jitter in how the cels were
| placed on the backgrounds, in addition to jitter of the whole
| frame. It's not so easy to stabilize it out. It would be cool to
| clean that up too with modern techniques.
|
| More speculatively it seems to me like AI is approaching the
| level of image understanding where it could draw new in between
| frames in a much, much smarter way than typical terrible frame
| interpolation. That would be a great project and potentially
| commercially valuable. Steamboat Willie is animated at 24 FPS but
| it's common for animated TV shows to be done at 8 FPS and they
| could really benefit.
| actionfromafar wrote:
| It doesn't look to me like Steamboat Willie is animated at
| anything close to 24fps. I couldn't step frames, but just look
| at the video, the animation is jerky. (Not worse than animation
| usually is, but it's not 24fps.)
| jlarcombe wrote:
| very interesting indeed, reminds me of some of the work done by
| Jamie Howarth and co with the 'Plangent Process' which uses the
| bias tone recorded by analogue tape machines to correct flutter
| on high-sample-rate transfers from tape...
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