[FFmpeg-user] DeckLink Duo 2 duplex_mode doesn't work

Moritz Barsnick barsnick at gmx.net
Wed Aug 7 17:30:31 EEST 2019

Hi Rik,
I don't have Decklink experience, but:

On Wed, Aug 07, 2019 at 15:04:32 +0200, Rik Roukens wrote:
> However, when I try to run the following recording command on DeckLink Duo
> (3) or (4), it doesn't work:
> ffmpeg -format_code Hp25 -f Decklink -i 'DeckLink Duo (3)' -duplex_mode
> half -c:v libx264 -preset ultrafast -map 0 -segment_time 20s -f segment
> /media/primary/rolrec-cam2/output%03d.mp4
> [decklink @ 0x55ff0e2022c0] Cannot enable video input
> I do not understand what I'm doing wrong, according to the manual
> <https://www.ffmpeg.org/ffmpeg-devices.html#decklink> you are supposed to
> add -duplex_mode half to the command to set the card into half duplex mode
> for the specified output.

"-duplex_mode half" is an input option. In order for it to take effect,
it must be placed *before* the "-i" to the decklink device.

> Does anyone have any idea of what might be going wrong?

Assuming that that option is missing for it to work, then my hint
should fix it. Please let us know. ;-)


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