[FFmpeg-devel] [PATCH] avdevice/decklink: adjust for timecode lag

[Gyan]

On 22-08-2019 01:10 AM, Marton Balint wrote:
>
>
> On Tue, 20 Aug 2019, Devin Heitmueller wrote:
>
>>> A couple of follow-up Qs:
>>>
>>> Is auto-detection available for all Decklink devices?
>>
>> No, but AFAIK it is for all devices which support SDI. Generally it's
>> the older analog capture devices which don't support it.
>>
>>> For those for which it is available, are there any edge cases in which
>>> it sets inaccurate mode?
>>
>> I don't trust the existing detection code enough to use it in
>> production.  It often fails to detect and thus ffmpeg will exit at
>> startup.
>
> Can this be fixed by simply increasing the timeout from 1 sec to 2 
> seconds?
>
>> Also, there are cases where it will misdetect 1080i59 as
>> 1080p30 depending on the card.  It's been on my TODO list for a while
>> to make that code more robust (I believe I know what most of the
>> issues are), but it hasn't been critical for any of my use cases.
>
> Hmm, interesting... When you say the issue is card-dependant, does 
> this mean card _model_ dependant or that the issue can affect one card 
> and not the other with of the same model/fw?

If an user can't or won't use format auto detection, then there is no 
way to reliably obtain the correct timecode without this patch or some 
similar hack.

Maybe the offset-related ops could be guarded by a check for auto 
detection, even though the patch won't hurt even if it was used in that 
case.

Gyan