[FFmpeg-devel] [PATCH] doc/outdevs: Add declink signal generator example

[Marton Balint]

On Thu, 15 Mar 2018, Mike Goins wrote:

> On Fri, Mar 9, 2018 at 3:38 PM, Devin Heitmueller
> <dheitmueller at ltnglobal.com> wrote:
>>
>>>> +ffmpeg -re -f lavfi -i "testsrc=s=1920x1080:rate=30000/1000" -f lavfi -i "sine=frequency=1000:sample_rate=48000" +        -ac 2 -acodec pcm_s16le -pix_fmt uyvy422 -format_code Hi30 -f decklink 'DeckLink Studio 2'
>>>
>>> You should not need the -re flag, the decklink outdev blocks if it gets too many frames and because of this the "encoding" speed should be limited to realtime even without -re. Or you see something different?
>
> If don't use -re I get an average of ~31 fps and speed 1.03x, but with
> -re the status stays at 30 fps and 1x.  No idea why the difference.

I'd say that is due to the initial buffering, it should smooth out to 
1.000 in time. So I'd avoid -re because it depends on the local computer 
clock.

Regards,
Marton