Answer of FAQ

How do I reduce the size of the exported AVI, FLV or MPEG videos?
There are multiple strategies for reducing the file size of exported videos. The strategies depend on whether a lossless output format such as FLV or a lossy format such as AVI or MPEG is used. In the first section, strategies for the lossless FLV format are described. In the second section, you will find strategies for lossy formats such as AVI or MPEG.

The following strategies work well for reducing the file-size of the FLV (flash)-output:

  • reduce the frame-rate from the default 25 to, say, 10, by using the commandline option "--fps 10"
    Please experiment which frame-rate is still within your quality requirements.
    It depends a lot on what you are actually recording. For many applications, a frame-rate of 10 still looks pretty good.

  • scale the video to a lower size and resolution.
    Scaling is done with a high quality anti-aliasing algorithm, so the result may still look very good.
    How much of scaling still looks good really depends on what you are recording.
    Scaling can be done with the commandline option "--resolution 512x384" (replace the numbers with numbers of your choice)

  • While recording, avoid unnecessary movements of the mouse-pointer.
    Movements of the mouse-pointer contribute a lot to the size of the video.

  • If your recording does not contain audio, please disable audio in the exporter by using the option "--no-sound"
So, for example you get a commandline like

    demorec-to-flv-with-player --fps 10 --resolution 512x384 --no-sound ~/demorec/yourvideo yourvideo.flv

For AVI or MPEG output, we suggest the following strategies

  • reduce the frame-rate from the default 25 to, say, 10, by using the commandline option "--fps 10" and at the same time reduce the output-bitrate by the same amount.
    Please experiment which frame-rate is still within your quality requirements.
    It depends a lot on what you are actually recording. For many applications, a frame-rate of 10 still looks pretty good.

  • scale the video to a lower size and resolution.
    Scaling is done with a high quality anti-aliasing algorithm, so the result may still look very good.
    How much of scaling still looks good really depends on what you are recording.
    Scaling can be done with the commandline option "--resolution 512x384" (replace the numbers with numbers of your choice)

  • While recording, avoid unnecessary movements of the mouse-pointer.
    Movements of the mouse-pointer contribute a lot to the size of the video.

  • If your recording does not contain audio, please disable audio in the exporter by using the option "--no-sound"
  • Please experiment with the output bitrate. Lowering the output-bitrate will decrease file-size but will also decrease quality. Which quality you prefer really depends on your requirements.
    The output-bitrate may be set with the option "--output-bitrate" and is specified in kbits/sec, so for example "--output-bitrate 1000" specifies 1000kbits/sec.
    The defaults are as follows:
    for AVI, MPEG4 and MPEG1:
    2000 kbits/sec
    for MPEG2 and VOB:
    6000 kbits/sec
  • So, for example you get a commandline like

        demorec-to-avi --fps 10 --output-bitrate 1000 --resolution 512x384 --no-sound ~/demorec/yourvideo yourvideo.avi


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