Correcting the speed of American programmes

Just wanted to bring this up because it came to mind a lot over the Christmas break. As most of will probably know, when American programmes are shown over here, the increase from 24fps to 25fps causes a subtle change in playback speed, as it does on home video before Blu-ray came around.

Personally I have an ear for things that don't sound quite right, especially when there's a song in a movie or a theme tune I'm quite familiar with. My family were watching some Fresh Prince when it popped up on Sky Comedy and I found the higher pitch of the theme tune to not only be noticeable but quite distracting. I must be in a minority because nobody in the room could pick up on it.

As any normal person does, I'd recorded Planes Trains and Automobiles on Channel 4 because I was curious to see how they'd edit the infamous profanity-laden scene when Steve Martin's rental car hasn't shown up. I'm quite fond of the soundtrack of this film, and having used the Blu-ray to watch it the last few times, I expected the music to be unpleasantly fast. It could've just been me, but it sounded like it does on the Blu-ray at 24fps.

Anyone who's spent ten minutes in a video editing program knows it's quite easy to change the playback speed and pitch of a video. Assuming Channel 4 went to the effort of getting the film to play at the correct speed, how come UK broadcasters seem content with playing out programmes and films faster than they should? Laziness? A subtle opportunity for more advertising time?

Of course, if I've just misheard the music in PT&A, then this post is completely redundant and I apologise

"Correcting" it might end up being more of a problem - presumably to "correct" the speed of a show at 24fps to 25fps you end up having to play one of those frames twice per second, which might just end up being jumpy. Most people won't notice a show being played slightly faster - and frankly for most broadcasters that extra minute or two of ad time you get as a result is going to be welcome.

Fresh Prince was an NTSC to PAL conversion though, as it was an electronic studio sitcom shot at 59.94 fields per second. No speeding up should have been done, unless somethings gone very wrong.

I asked about that on here a while back, as to why 29.97fps to 25fps resulted in faster playback instead of slower. Had something to do with the programme being converted to 24fps with the original speed intact. I can't remember the technicality behind it to be honest.

If you are filming for American tv you would shoot at 24*1000/1001 so,that you can do 2/3 pull down
Into N/ATSC Rates. 30*1000/1001.

These day conversion between tv standards of a file is potentially just a matter if re rendering the interpolated frames at the right time ....
and good one can tell where a 2/3 pull down had been edited .... and correct..
And if you want to put 2/3 pull down into a USA version ...

But if the material is on film it has be customary to run at 25 FPS and thus shorten the programme and frequency shift the audio.

One question about the OP mentioning the Fresh Prince though... that show was shot on video, so why would it have the PAL speedup when it wasn't shot at 24fps to begin with?

Well if it was done on videotape in the US wouldn't it have been at 30fps (give or take)? I know its not as simple as slowing it down to 25fps (refresh rates and all) but in theory the soundtrack should be slower?

I don't think you slow down from 60i to 50i, you use various methods that remove or blend fields instead, no speed change.

Well, technically the us is 59.94i, and maybe they speed that up to 60 to make the conversion simpler, but even then if they do, it's a speed up of around 0.1% so shouldn't really be detectable even to people who do notice these things.

Theres an episode or two of Scrubs that are "slower" than the others, which I'm assuming was down to a conversion error when making it suitable for PAL broadcast and it was never noticed or corrected. It was like this when the show was on 5 STAR as well as on E4 and 4 Music so I'm assuming its an error with the source and not something to do with how the UK broadcasters put it out.

But zooming in the 4:3 picture to make it 16:9 by losing the top and bottom IS down to the broadcaster and something that's really annoying about the show on 4 Music. It's in 4:3 on All 4. Other 4:3 programmes are either cropped also or stretched horizontally to fill the 16:9 frame so everything looks distorted and wide. At least on All 4 the show is uncut too, compared to the awful daytime edits on 4 Music.

I'd be very surprised if Channel 4 played PT&A at the correct speed. 24 just doesn't go into 25, so your options are either to repeat one frame every second (you could do it at field level, but that's just asking for more trouble), or to play it fast and adjust the audio.

One rare example of the latter was Torchwood: Miracle Day, presumably because it was thought that UK audiences would be too likely to notice the pitch-shift on the familiar character's voices. It made it an ache to watch for me, though, as years of video work has left me sensitive to stuttering video.

(Fresh Prince shouldn't have suffered any of this, because it was shot and edited on video, not film. The video would have been fully standards-converted which would have made it a bit blurry at times but wouldn't have affected the speed)

If you just speed up the audio, you get a pitch shift. That's what usually happens, as you've noticed. But you can do more a convoluted adjustment which changes the speed to match the video, but doesn't change the pitch. It's one of those things that doesn't have an exact mathematical solution, though.

Channel 4 has form for experimenting with this. Enterprise and Stargate SG1 were given this treatment in the noughties, but not with a great deal of success. There was a definite "warble" to the audio.

I think they also tried the same thing on a broadcast of the film The Spiderwick Chronicles , which was even worse. The audio was bubbling all over the place.

But perhaps they've finally (more or less) perfected it. It reminded me of the DVD release of Stardust , because I found to my surprise that the Take That song over the credits was the correct pitch, though now I think about it they may have just redone the credits for PAL territories.

They may have done this to the recent series 1-4 blu-ray boxsets of Doctor Who , which they slowed down to 24fps so they only needed one master. (On the Specials, and on the Day of the Doctor blu-ray, they inserted additional fields to get it up to 60fps which made for stuttered viewing. More info here: http://horman.net/doctorwho/specials.php

Pitch-shifting came up once in an interview. Jack Coleman, who played Noah Bennet in Heroes[i], was interviewed on [i]This Morning and mentioned that his voice sounded weird when he watched an episode in the UK. He asked Phil why, but I don't think Phil knew.

I have the Sabrina the Teenage Witch DVDs, and the episodes on there seem to be a mix of ones that are sped up, and ones on which a standard NTSC>PAL conversion has been done on the footage and they play at normal speed (but have jerky motion as a result). Most episodes are the latter (which stuck out to me at first with the voices sounding deeper than I was used to), most of the speedup episodes are on seasons 2 & 3.

The ones that have been sped up have been de-interlaced too- as you can tell from the effects on the title sequence and the animated scene transitions(obviously the show itself was shot on film, but those bits are 60i video effects), whereas the ones that aren't sped up are still interlaced.

Whenever I've seen the Channel 4 early morning repeats of Cheers over the last couple of years, they also seem to be at the normal speed, which again sounds odd after I got used to the DVDs, which are sped up.

Speaking of The Fresh Prince though, the versions on the BBC iPlayer seem to be filmised for some reason, even though the iPlayer is one of the few streaming services to (usually) run videotaped content at 50fps. It is encoded at 50fps, in fact it's upscaled to 720p50, but has been filmised somewhere along the way.

That's not how I remember it, and Wikipedia says it was shot on videotape. Are you sure it wasn't el-cheapo 60->30 fps?



I've just download an iPlayer episode at random and the pans are remarkably smooth and stable at 25fps. Comparing it to a YouTube video of the same episode (30fps, every other frame dropped), I found that per shot/scene, the BBC version has exactly 80% the number of frames, not the 83% you'd expect of a straight NTSC to PAL conversion, and it does seem to be running fast. The video quality's also a lot higher than I remember it being on first broadcast in the 90s.

So, at a guess... for reasons best known to themselves, the distributor made a high quality motion-compensated conversion to 24fps (not adjusting playback speed), and the BBC sped it up to 25fps.