Dropping Frames...The Notice Factor

[Tom Saurus]

I think idealy when one is recording a movie or tv show that they feel is important to archive, that no frames are dropped. Should one feel terribly bad if out of a 90 minute movie some 170,000 frames get captured, and one gets dropped? I had a situation like that yesterday, and part of me felt like "just delete it, it will come on again and then try to capture it again without one frame being dropped", and part of me felt like how could I possibly notice one frame not being there when watching it on tv; because one gets thirty frames a second. 1/30th of a second would go by pretty fast, but yet I feel bad about it anyway.

What is your oppinion on such things? I am curious what other people feel about this topic.

[FulciLives]

It shouldn't be an issue i.e., it shouldn't throw off A/V sync at least not to any degree that you would even remotely be able to tell. Also sometimes a frame is dropped here or there to keep the video in sync with the audio so there may not even be a 1 frame A/V desynch issue, you know?

- John "FulciLives" Coleman

[JohnnyMalaria]

I've been rigorously testing our new app for dropped frames and stumbled across the following observation...

I captured 3.5hrs of DV without one lost frame (over 370,000 frames). This was done when an equally huge, previously captured file was playing back from the same hard drive. I was quite happy with that.

Then I tried again and, much to my consternation, it dropped a couple of frames. It didn't make much sense and I set about trying to understand what caused it. Well, to generate a long and interesting DV file, I used the analog output from standalone DVD player, fed it into a Sony DSR-11 DV deck and captured the DV from the deck. I found I could reproducibly drop the same frames from the same part of the incoming video. The DVD was concert footage with lots of flashguns going off. One of the flashes was causing the dropped frames - either because the DSR-11 was getting overloaded or the analog signal was out of spec from the DVD player. Further playing about revealed that I would get dropped frames when I would turn the DVD player on and off - presumably, the DV deck was trying to genlock to the DVD player's signal and creating timing issues when the player was turned on or off.

Of course, it didn't help resolve the two dropped frames but at least I knew it wasn't something my software was doing wrong!

[Tom Saurus]

FulciLives: Thank you for input, it was kind of you to take the time to respond to my questions.

[SatStorm]

10 frames per hour, won't be a problem. 1000 frames per hour is a huge problem!

Most capture programs, have ways to keep A/V syncronization, even with a great amount of lost frames. Mainconcept Encoder's capture plug in for example, is notorious on this (but very CPU demending also...)