Gentoo Archives: gentoo-user

From: Stroller <stroller@××××××××××××××××××.uk>
To: gentoo-user@l.g.o
Subject: Re: [gentoo-user] [OT] using ffmpeg for screen cast
Date: Mon, 27 Jun 2011 11:10:09
In Reply to: Re: [gentoo-user] [OT] using ffmpeg for screen cast by Mick
1 On 26 June 2011, at 19:54, Mick wrote:
2 >>> ...
3 >>> ffmpeg -f x11grab -s xga -r 25 -i :0.0 -aspect 4:3 /tmp/out.mpg
4 >>>
5 >>> but the result is rather blurred as you can see in the attached
6 >>> screenshot, when I play it with mplayer.
7 >> ...
8 >> Try passing "-sameq"
9 >
10 > WOW! Exceptional improvement in a single stroke! Thanks! :)
11 >
12 > Why is it that ffmpeg degrades the quality with default settings? What does
13 > it assume that the setting is? (sorry for the newbie Qs, but this area is
14 > until now outside my cognitive map! ;-)
16 I don't know about the "default" settings, but I would interpret the file extension of your original command as telling mplayer that "the destination file should be encoded as mpeg2". This is a pretty poor codec by today's standards.
18 I could well be wrong, though. Do you know what format the output file is?
20 IMO you're best encoding to h264 (in an mp4 container) for distribution, but I think it's possible the encoding load of that might affect your screencast. So you might wish to use sameq or the r210 or rawvideo codecs and then transcode to h264 (or WebM or whatever) afterwards.
22 > Now, I hope I'm not getting greedy, but how do I add voice recording to the
23 > above stanza? Or do I have to record voice and then package it along with the
24 > video in a container as a separate step?
27 Video and Audio grabbing
28 FFmpeg can grab video and audio from devices given that you specify the
29 input format and device.
31 ffmpeg -f oss -i /dev/dsp -f video4linux2 -i /dev/video0 /tmp/out.mpg
33 Note that you must activate the right video source and channel before
34 launching FFmpeg with any TV viewer such as xawtv
35 (<>) by Gerd Knorr. You also have to set
36 the audio recording levels correctly with a standard mixer.
38 Audacity is widely used for simple audio editing.
40 Stroller.


Subject Author
Re: [gentoo-user] [OT] using ffmpeg for screen cast Mick <michaelkintzios@×××××.com>