[Bug 771734] Add support for duplex mode configuration to decklinkvideosrc

[GStreamer (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=771734

Florent Thiéry <florent.thiery at ubicast.eu> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|NOTABUG                     |---
            Summary|decklink internal data      |Add support for duplex mode
                   |stream error with           |configuration to
                   |device-number 2 and 3       |decklinkvideosrc

--- Comment #14 from Florent Thiéry <florent.thiery at ubicast.eu> ---
Apparently, the latest SDK (10.8) allows configuring the duplex mode using
bmdDeckLinkConfigDuplexMode (in this case, trying to use input 3 would require
disabling full-duplex mode on inputs 1&2 which are linked); would it sound
right to automatically reconfigure the mapping instead of failing like it does
today ? Also, is the current behaviour good enough (Internal data stream error)
?

Unfortunately the return code #define E_FAIL ((HRESULT)0x80000008L) is
completely generic, so it doesn't indicate wheter the channel is just unmapped
(a quick helpful error message is not an option then)...

AFAIK the full-duplex feature is designed for looping out the input, but also
performing hardware-based keying -- is that an actual use-case for gstreamer
currently (hence, a reason for not disabling full duplex when trying to open an
unmapped channel)?

I tried to query if the device supports duplex mode
(BMDDeckLinkSupportsDuplexModeConfiguration and getting
BMDDeckLinkPairedDevicePersistentID) but it's not in the current headers
included in gstdecklink (only in the latest SDK headers). Also, when i query it
for BMDDeckLinkSupportsFullDuplex, i always get 0 as return code (on all
inputs), so i think that the SDK needs to be updated anyway (the card i'm
trying to use is probably more recent than the current SDK release).

As a workaroud, users can use the BMD utility to disable full duplex on
channels 1 and 2, which enables capture channels 3 and 4, but i still believe
it would be good to support this, if you don't mind i would like to reopen this
ticket and adjust the title.

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