[FFmpeg-user] DeckLink Output Controls
reuben.m at gmail.com
Sat Oct 8 22:53:08 EEST 2016
On Friday, October 7, 2016 5:25:10 PM CDT Matthias, Thomas wrote:
> Hi There,
> I’m looking into using FFMPEG for its DeckLink device control. The capture
> part of the API seems fairly fully featured, however the output/playback
> controls seems to have some strange limitations. Specifically, on output,
> there is a hard-coded limit of only 8 channels of audio.
HDMI is limited to 8 channels. Sombody somewhere probably didn’t want to
implement the logic required to make channel limits depend on the output
> What’s strange,
> is that the capture partition can handle up to 16, which makes sense
> considering most DeckLink cards have SDI input/output, and 16 channels is a
> standard workflow for SDI. Also, is there a reason why only 2 and 8
> channels are supported, instead of just “n” channels (4 or 6 channels, for
HDMI offers stereo mode, and 8 channel mode when using PCM streams. There is
no a’la-carte audio mode. Dolby / DTS has things like 5.1, but that is an
entirely differnt stream type separate from PCM.
> Would it be possible to output 16 channels of audio? Is there a better way
> to do this (via the command line?)? Could a custom version of the
> decklink_enc files be built to handle 16 channels or is there some other
> limitation I’m not aware of?
Probably. Depends on what the API supports.
> Thanks in advance, I really appreciate any advice/ideas here. Also, is
> there a specific reason that input/output are limited to only 48khz for
SDI is 20bit 48k audio only. There’s really no good reason for anything else.
Technically SDI also supports 48048 and 47952 to allow for pull up/down, but I
think that is done by manipulating the clock rather than explicitly changing
the sample rate.
More information about the ffmpeg-user