How would a VCR play tapes too fast?

[aramkolt]

Was watching this YouTube video where the user was comparing a blu-ray release of a film to his genuine VHS copy and he found that his VHS copy was playing about 5% faster than the blu-ray. This isn't something I've heard of before - you'd think it'd cause some significant issues, but maybe not if the issue is that it is playing fast since the card or TBC would just start dropping frames every 20th frame or so maybe?

This link goes right to where it is discussed (10:43):
https://www.youtube.com/watch?v=jrvih1gSN4w&t=643s

I assume if it can happen with commercially released tapes that it could also happen with other tapes. I'm sure the actual causes is related to the drum/capstan speed feedback which probably works on FG/PG pulses, but I'm kind of surprised that there are no other actual playback issues created by this.

I wonder how fast or slow you could potentially (purposely) watch a tape in regular play mode on a CRT and have zero tracking issues etc? Sounds like an interesting party trick.

My question is - how would you normally know that this is happening? I assume you'd just get tons of dropped frames during a digital capture? However, if it was going through a frame TBC first, then it'd drop those frames without telling you.

Wondering if anyone here has ever come across this?

I wonder if for a tape playing fast if the linear audio track would be higher pitched than the hifi track to be noticeable?

I guess maybe the easier way to tell would be determining if the tape counter is accurate - by displaying the on screen the tape counter at the beginning of a long capture, then put it back right at the end and then see if your captured duration matches the elapsed time per the tape counter?

[Aya_Rei]

Copying the comment MintyRoot said

Quote:

You mention your VHS copy running 5% too fast, I don't believe this is an issue with your aging VHS player, but it might be due to owning the PAL copy. Since PAL runs at 25fps, they'll often just speed up the movie from 24 to 25 fps and pitch correct the audio, giving it a 4% speedup.

I've heard this is pretty common with PAL releases. So no need to get all crazy here, simple explanation is "Movie studio sped up movie so that the 24 FPS film works within the 25 FPS PAL standard"

[aramkolt]

Ah, That must be it!

On the tape, it shows an approximately 146 minute runtime: https://www.ebay.com/itm/356268546351

On the DVD, it shows 152 minutes as the runtime: https://www.ebay.com/itm/226945165597

The bigger issue would have been if the captured time didn't match the reported runtime on the tape, but that's not something I would have otherwise thought to check.

Learn something every day

[Aya_Rei]

Usually the reported runtime on a tape is never 100% accurate which is why they tend to write down the approximate runtime. Like a tape that is labeled to be 45 minutes might only have 42 minutes of actual content.

Was told that with Blu-Ray this whole speed up thing is dead as Blu-Rays can be watched at native 24 FPS, however movies are still sped up when broadcasted on TV.

Video games are the reverse, where the 60hz NTSC game is slowed down to fit within the 50hz PAL standard.

[dpalomaki]

FWIW: 146:152 corresponds to 24:25. matching the film to PAL ratio (144:150 would be exact).

[latreche34]

It's not easy to speed up the capstan motor without screwing the fields, The head drum is servo locked regardless the age of the VCR, so I don't believe for a second that the capstan can speed up or slow down without consequences.

[lordsmurf]

Quote:

Originally Posted by Aya_Rei

Copying the comment MintyRoot said
I've heard this is pretty common with PAL releases. So no need to get all crazy here, simple explanation is "Movie studio sped up movie so that the 24 FPS film works within the 25 FPS PAL standard"

Yep. This is the correct answer.

Any time differences tend to be in the conversion methods, or lack of conversions.

Trivia: In my earliest streaming studio days, converting PAL back to NTSC was a requirement. It was a PITA when the source was interlaced. It also didn't always match the automatic metadata, so I'd sometimes have to manually edit the sidecar files. After they saw the time costs of conversion (or the drastic lowering of quality with quick methods), combined with computers (and then-new HDTV) which were mostly PAL/NTSC agnostic, they removed that requirement from my workflow. It saved both money and quality, positive ROI.

[timtape]

We grew up with feature films on Australian TV running 4% fast on our PAL TV system, even Australian feature films. It was particularly annoying when already well known popular recorded music tracks appeared throughout the movie playing tonally sharp and with faster tempo.

I believe the initial reason for the change from "silent" film speed of maybe 16fps, to 24fps for the new "talkies" was the improved sound quality obtained plus of course somewhat smoother visual movement.