[FFmpeg-user] Capture from Decklink card on Windows 7 and display it (preview) and on demand record it (while still displaying/previewing).

[Bjorn Ramakers]

Hey,

Cant seem to wrap my head around this, seemingly easy, but cant put it all
together. I am using Windows 7 to accomplish this.
My requirement is to capture video+audio from a Blackmagic Decklink card
which delivers 720p from a video source.
This capture should be displayed (preview) and on demand I should be able
to record (and stop recording) the same stream to a file.

My initial though on how to solve this was having ffmpeg capture the
video/audio from the Decklink card and create a network stream. I would
have vlc player pick up the network stream and display that.

Now I would have a second ffmpeg process started and record the same
network stream to a file whenever it's needed.

This is the command I used to setup the network stream :

ffmpeg -f dshow  -i video="Decklink Video Capture" -f dshow -i
audio="Decklink Audio Capture" -r 60 -vcodec mpeg4 -q 20 -acodec libmp3lame
-ab 128k -f mpegts udp://127.0.0.1:6666?pkt_size=188?buffer_size=65535

Using VLC I tried to open this network stream via the address : rtp://
127.0.0.1:6666

But immediately I get the following error :

SDP required:

A description in SDP format is required to receive the RTP stream. Note
that rtp:// URIs cannot work with dynamic RTP payload format (65).


Following some posts I found on forums I tried to add > config.sdp after
the command I create the network stream with, but the file never gets any
input.


My question, would this be a good way to handle the requirements I have?
And if so, what should I do to create the correct SDP for the stream?


Many thanks in advance.


Best Regards,


Bjorn.