Video Capture On PC
This describes how we captured bird box video using a computer fitted
with a video capture card.
As the picture quality was inferior to using
a TV+DVD recorder, this approach has been abandoned for now.
The Equipment
I
resuscitated an old AMD Sempron 3000 based computer, plugged in 1GB of
RAM, installed an ancient Pinnacle PCTV pci card, and loaded Ubuntu
8.04 (Hardy) as the operating system.
Although we had lost the Pinnacle CD, the Linux 2.6 kernel supports the bttv chipset via a v4l (video for Linux) driver.
The Pinnacle PCTV card has a video input in addition to the rf
(analogue TV) input, so it can be used to capture composite video from
cameras, DVD players and other suitable video sources.
Running VLC to display video from the PCTV card requires a number of
settings or arguments. Its easier to create a desktop shortcut and
specify these arguments in the command line, for example:-
vlc -vvv --fullscreen v4l:/dev/video0:norm=0:channel=1
where --fullscreen displays at fullscreen, norm=0 is auto
mode (can set norm=pal or whatever country standard applies), channel=1 is composite video input.
(don't now what -vvv does).
To view and capture video using VLC requires a rather more complex command line:-
vlc
-vvv v4l:/dev/video0:norm=pal:channel=1 --sout
'#duplicate{dst=display,dst="transcode{vcodec=mp4v,vb=1024,scale=0.5,acodec=mpga,ab=64,channel=1}:duplicate{dst=std{access=file,mux=mp4,dst=/home/steve/Videos/myVideo.mp4}}'
where vb sets the video bitrate, ab is the audio bitrate, scale is
reducing the video to half size, and recordings are initially saved to
the myVideo.mp4 file.
The Results
The displayed video showed a lack of detail in the bright areas of the
picture. Basically more of the picture appeared to be "burnt out" that
the straight TV equivalent, and the lower density areas were "soft" and
lackinnng detail. I think the most likely cause is poor frequency
response in the PCTV card, although I suppose I should not rule out
some problem with the software...I may take a second look if time
permits.
It seems to me that selecting a consumer video capture card or USB
device is tricky, because there is no way from the published
information to determine how good or bad the picture quality will be.
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