Re: Video motion tracking and speed estimation

On a sunny day (Sun, 15 Mar 2009 17:54:06 -0500) it happened "Anthony Fremont"
<nobody@xxxxxxxxxxx> wrote in
<2N6dndU0N42NGiDUnZ2dnUVZ_vvinZ2d@xxxxxxxxxxxxx>:

I can get YUV from the linux driver too, but I went with RGB instead. YUV
might have advantages that I could use.

As you are using a composite camera, the signal is already split into Y and U +V for the color.

The idea of YUV is that you need less resolution for color vision, so many times
the signal is transmitted as YUYV, or YUVYUV, where U and V each have 1/4 the resolution as Y.
Anyways, there are many formats for that sort of encoding, but I have sort
of standardised on the 'mjpegtools YUV format'.

That has a number of advantages.
You know about Unix pipes, for example you can do:
cat file.txt | grep 'Hello"
where 'grep' is used as a filter to only get 'hello' through (if it is in the file.txt).

The mjpegtools project created a simple format to send YUV (color video of any format)
from one application to the next.

This means you can do filtering, resizing, displaying, encoding, even sending via the net
*without needing intermediate files*.

YUV format (uncompressed) files are huge.
But now we can do for example this, to send a H264 stream via the internet:
camera | scaler | encoder | netcat

Or use a lowpass to get rid of noise:
camera | filter | scaler | encoder > H264.avi


As mjpegtools yuv allows you to chain things, you can for example lowpass filter, de-interlace,
resize, and even feed it back into a v4l device and have flashplayer use it so it is broadcast
to many other users via some sites, for example for video conferencing.
http://mjpeg.sourceforge.net/

There is a whole lot of tools in that package, xine, mplayer, and ffmpeg can read the format.

An other advantage of working with YUV in general is that you can process color and BW content separately.

last but not least I wrote 'subtitler-yuv':
http://panteltje.com/panteltje/subtitles/index.html
that program can be used in the chain of filters, to not only add subtitles, but also scrolling text,
pictures, and do fade -in fade-out of those objects, change their color, all controlled from a simple
text file with frame accuracy.
I use it to make my youtube videos... together with the transcode package.

.

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