[time-nuts] Re: Where do people get the time?

[Lux, Jim]

On 1/2/22 12:39 PM, Peter Vince wrote:
>
> I used to work in broadcast television, and find that most people would
> notice a couple of "frames" (80ms here in the UK) - we, trained and looking
> for it, would notice one frame (40ms).  But it is more disturbing if the
> sound is early, as that is so unnatural.  At that sort of level though, it
> is quite hard to tell if it is early or late, especially as the actors
> won't just stand there saying the same thing time and again :-)
>
> Because the sound and video don't use the same frame rates, MPEG codecs
> have a hard time getting it right.  We developed a test signal which
> measured the time between a blip on the sound and a flash on the vision,
> and used it regularly when lining up links.


The curse of the USB 8 kHz frame rate (derived from telephony, of course).

Neither 24 nor 60 divides into 8000 evenly. 50 does, but that's cold 
comfort for the US centric industry.  And let's not even talk about 
59.94 or 29.97 for NTSC video.