[FFmpeg-user] Blackmagic DeckLink Quad 2

[Robert Frazier]

Thank you so much for your help, Moritz!

On Thu, Jun 7, 2018 at 7:12 AM Moritz Barsnick <barsnick at gmx.net> wrote:

> On Wed, Jun 06, 2018 at 15:52:48 -0600, Robert Frazier wrote:
>
> > *ffmpeg -video_size 1280x720 -pixel_format uyvy422 -framerate 60 -vsync
> > > drop -f dshow -rtbufsize 150M -i video="Decklink Video Capture (5)" -i
> > > video="Decklink Video Capture" -i video="Decklink Video Capture (5)" -i
> > > video="Decklink Video Capture" -an -filter_complex
> "[0:v][1:v]hstack[t];
> > > [2:v][3:v]hstack[b]; [t][b]vstack" -c:v libx264 -preset ultrafast -f
> mpegts
> > > pipe: | ffplay pipe: -vf scale=1280:720 \ pause*
> [...]
> > > video=Decklink Video Capture: No such file or directory
>
> I don't use Decklink, but what you did is to provide the input options
> "-pixel_format uyvy422 -framerate 60 -f dshow" only to the first input
> "-i". The three others ffmpeg doesn't realize are DShow devices. You
> need to provide your input option before *every* input.
>

This definitely was my problem. I've had syntax errors this whole time, how
embarrassing! My program works now at least, albeit kind of slowly, with a
lot of overused buffer errors, and some occasional hiccups loading all my
videos. Any tips on cleaning up latency and buffers perchance?


>
> > So my optimistic concern is just that I'm using the wrong naming
> > scheme;
>
> Wrong syntax, actually.
>
> > my only other idea is that I can't read two streams from the DeckLink
> > card simultaneously (though I feel like I've read I can).
>
> I have no idea, but my guess is that it will work.
>
> > streams does not run with frame rate set to 60fps, I need to set it to
> > 59.94fps to work, otherwise it is a black screen.
>
> That may be a Decklink limitation, or have to do with the actual input.
> BTW. 59.94 is also wrong or at least inprecise, you should probably
> write it as "60000/1001", as ffmpeg accepts rationals.
>

This part as it turns out, is probably just a fluke on my part. Yesterday
that input would only take 59.94, but today I started with a different test
video loaded, and it is happy to use 60. So I'll just have to be careful to
check those before hand, but I will keep in mind the fractional form.


>
> Cheers,
> Moritz
>

Many thanks!
Robert


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