[ubuntu-us-mi] screencasting Ubuntu

[Scott Moser]

On Tue, 10 Feb 2009, Robert Citek wrote:

> Thanks, Tony.  Lots of good info in that thread.  Cinelerra, Kino, Blender.
>
> What have folks here tried?
>
> When I went from ogg to avi and back to ogg using ffmpeg, the quality
> suffered tremendously.  What was your experience with converting it
> from ogg to dv?
>
> BTW, I'm using Ubuntu 8.04.

all video compression is lossy (like jpeg rather than png or "raw").
the more advanced video codecs (mp4, ogg) gain their small size and high
playback quality with lots of tricks that largely come at the cost of
editing.

I would guess that it is possible to do "in place" ogg or "mp4" editing,
but I'm not aware of any software that does it.  Even then, you'd get
lossy re-compression on at least parts of the frames that you modified.
Outside of that you're going to be stuck with converting to a more
edit-friendly format.  mjpeg and dv formats end up with much larger
files that are more easily editable... mjpeg is essentially a jpeg for
each frame.

"Non-lossy" editing tools do exist for compressed audio
(http://freshmeat.net/projects/mpgedit/ is one)

The key for video editing is:
- do your edits/saves "all at once", such that you only suffer one lossy
to lossy conversion.  I know in my very limited experience with kino
that it is quite easy to "save" multiple times, which end up doing lossy
saves each time and thus more data gone.

- make sure that your conversion from ogg/mp4 -> editable-format is done
a the highest quality.  Ie, if the video is 640x480 native resolution,
you dont want to convert it to 320x240 mjpeg and then edit.

If you do everything well, the lossy->lossy conversion wont be *that*,
possibly not even noticeable.  But, you're never going to get the same
quality as the source.