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

Marton Balint cus at passwd.hu
Fri Mar 9 22:58:44 EET 2018

On Fri, 9 Mar 2018, Devin Heitmueller 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?
> Also, isn’t -format_code a capture parameter?  Is it even valid to provide that on output?

Yes, it is capture only indeed. Wonder why does ffmpeg accept it in the 
first place?

> I had plans to add support for -format_code for output - if it’s already working then that’s great.

The decklink outdev finds the correct mode by searching for the 
properties (frame rate, field order, dimension) of the stream which is 
provided to it. So specifying the format_code should not be needed.


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