[nycbug-talk] Screencasts using ffmpeg [PARTIALLY SOLVED]

Eric Radman ericshane at eradman.com
Wed May 9 22:37:23 EDT 2012

----- Forwarded message from Eric Radman <ericshane at eradman.com> -----

Date: Tue, 8 May 2012 08:33:59 -0500
From: Eric Radman <ericshane at eradman.com>
To: talk at lists.nycbug.org
Subject: Screencasts using ffmpeg
X-Mailer: Mutt 1.5.21 (2010-09-15)

> Has anyone used ffmpeg for doing screencasts? FreeBSD 9 and OpenBSD
> 5.1 both deliver 4fps

I don't have a good solution yet, but I learned that the framebuffer
read rate is primarily bandwidth limited, and a feature of the hardware
and video driver [1]. I never noticed before, but x11vnc prints an
estimate of the throughput when you start it

09/05/2012 22:23:45 fb read rate: 7 MB/sec

One interesting solution is to disable hardware acceleration by adding
Option "ShadowFB" "true" in the Device section of the xorg.conf. This
will keep a copy of the framebuffer in main memory where can be read
at high frame rates.


[1] http://www.karlrunge.com/x11vnc/#limitations

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