Producing Video Clips of JFORCES


Two programs, ffmpeg and xvidcap, are required to capture screen activities for incorporation into video productions. These programs are not generally installed as part of a standard Linux installation, so they will have to be installed manually. To do this ffmpeg must be installed first. Download the source either from the JFORCES download site or go to www.sourceforge.net to get the latest version. At this date it is only available in source version, so it will have to be compiled on the target machine. To do this:


  1. log on to the target computer as root
  2. extract the source code as follows:
  1. Assuming all went well, xvidcap can now be installed. This is similar, except it is mandantory to verify that the configure step recongnized the presence of ffmpeg. In my case I had to force xvidcap to recognize the presence of xvidcap as described below. Here are the steps, with notes on critical items to look for and manual steps that might have to be made.

checking for img_convert in -lavcodec... no

checking for avienc_init in -lavformat... no

./configure --with-forced-embedded-ffmpeg 


At this xvidcap is installed and can be tested by typing 'xvidcap'. But it's more convenient to setup xvidcap to automatically save the screen captures by creating a ~/.xvidcap.scf configurution file. My current file follows for reference:


# xvidcap configuration file
# frames per second
fps: 5.000000

# file pattern
file: capture-01.mpeg

# max frames
max_frames: 0

# max time
max_time: 0.000000

# quality (JPEG)
quality: 15

# compression (PNG, GZIP)
compression: 0

# use shared memory
shm: 16

# video codec used by ffmpeg
codec: mpeg4

# what kind of mouse pointer should be recorded? 0 = none, 1 = white, 2 = black
mouse_wanted: 2

# toggle audio capture (0/1)
audio: 0

# device to grab audio from
audio_in: /dev/dsp

# sample rate for audio capture
audio_rate: 22050

# bit rate for audio capture
audio_bits: 32000

# number of channels to use in audio capture
audio_channels: 1


This file sets the output to MPEG4. This appears to produce the best quality video in the smallest file; an important consideration since the expectation is that these video files will be downloaded via the internet. This file disables audio capture; the expectation is that narration will be added at a later time using a video editor.


Be forewarned that there is a problem in using MPEG4 as an output format. MPEG4 is not a common format, so many standard video players and editors will not work with the resulting file. Go to www.divx.com and download (and install) the latest DivX playter to get a good video player for MPEG4 on MS windows machines. By good fortune this program will install a codec on the the Windows PC, permitting both the standard MS Windows Media Player to play the files and the MS Windows Movie Maker to edit the files and add narration. To date narration has been added through the MS Windows Movie Maker. The only problem with this is the resulting format can only be saved in .wmv (Windows Media Video) format. This is good in that it can be viewed on any standard Windows PC configuration, but takes more space and reduced video quality. An MPEG4 editor would offer a superior solution, but no good public domain MPEG4 video editor has been identified to date.