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

[Marton Balint]

On Wed, 14 Aug 2019, Marton Balint wrote:

>
>
> On Wed, 14 Aug 2019, Gyan wrote:
>
>> 
>> 
>> On 09-08-2019 04:59 PM, Ilinca Tudose wrote:
>>> Hi Marton,
>>> 
>>> The issue with the out of sync TC was reproducible on all tapes and decks
>>> that we tested. I don't have the exact number now, but a few dozens, less
>>> than 100. They all had between 7 and 17 frames out of sync. We were not
>>> able to obtain anything more in sync than 7 frames.
>>> 
>>> The TC sync was tested by setting up the deck to "burn" the TC with the
>>> image while capturing the content with TC through ffmpeg. We then play the
>>> file in a player that supports timecodes and compare the burned-in TC with
>>> the one captured in the metadata.
>>> 
>>> We used Decklink quad 2 and several Sony decks: J30, J3, JH3. We tested on
>>> multiple decks from each model and confirmed the issue was present + that
>>> Gyan's patch seemed to fix it. We have used several types of Betacam tapes
>>> and HDCAM tapes. I can not comment on whether this is the best solution,
>>> but can confirm it works.
>>> 
>>> Let me know if you need more info.
>>> 
>>> Thanks,
>>> ilinca
>> 
>> Ping.
>
> Sorry, I need a bit more time to investigate.

OK, I did a couple of tests myself for HD and SD pal signals, and it seems 
to me if signal autodetection is used, so no format_code is specified 
then timecode is readily available in the first frame. I was using 
BlackMagic SDK 11.1 for testing by the way. Can you confirm the same 
behaviour with your setup?

Because that would make the patch uneeded I believe.

Thanks,
Marton