[FFmpeg-user] Decklink timestamp_align, what should it do?

[Bouke]

> On 2 May 2021, at 11:02, Marton Balint <cus at passwd.hu> wrote:
> 
> 
> 
> On Sun, 2 May 2021, Bouke wrote:
> 
>> From the manual:
>> 'timestamp_align
>> Capture start time alignment in seconds. If set to nonzero, input frames are dropped till the system timestamp aligns with configured value
>> 
>> Ok, when I put -timestamp_align in my command, it  does wait ‘a bit’ before starting capture.
>> That’s what I’m after, but i have no clue how long it waits. It’s not a ‘wait X seconds’ for sure.
> 
> It waits until UTC modulo timestamp_align becomes 0. So for 60 it waits until a full minute boundary is reached.

Ok, but what is ' UTC modulo’ ?
If i enter 0, it starts capturing immediately, higher values do give ‘a’ delay, but it’s not predictable at all.
(It’s off by a random value, up to 30% difference from what I expect…)

Bouke


> 
> Regards,
> Marton
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