[PD] pix_video: composite or Firewire ?
simonxwise at hotmail.com
Fri Nov 16 10:39:47 CET 2007
On 16 Nov 2007, at 10:47 AM, Alexandre Quessy wrote:
> I didn't like much using Firewire (ieee1394) under GNU/Linux, since
> the driver is pretty slow.
As I understand it, if you are using DV codec with firewire you are
going to get several frames delay (on any OS) - I guess this system
is optimised for capturing media for editing, favouring accuracy
rather than latency, not so good for real-time use. I have tried many
different combinations of DV camera and capture system, always there
are several frames delay with DV. Composite capture cards can be much
faster, and can be better resolution too - but they get very
expensive for higher resolutions. Without locking the camera's
framerate and the capture card together you are always going to get a
frame or more delay. Very high end digital mixing systems have a
exactly one frame delay, allowing for processing the signal etc and
all the cameras are locked in sync.
I settled on a PCI framegrabber from Eurosys, not cheap but quite
nice, and get a delay of less than 2 frames - just fast enough to get
away with putting the image of a performer speaking up onstage
without the sync between live voice and image being too bad.
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