Make some noise

I adapted Geek Thoughts‘ “Making Noise with ImageMagick” in creating video noise — a video simulating what you used to get when you turned on a television with no signal, back in the analog days. To combine the noise frames created by ImageMagick I used Netpbm, which I had to install separately (that is, it wasn’t installed by default in Lenny).

Here’s the Bash multi-liner I used to generate 48 frames worth of noise:

(for i in `seq 1 48`; \
do convert -size 640x480 xc: +noise Random \
-blur 1x1 -fx intensity -normalize ppm:-; done) \
| ppmtompeg kohina.txt

And here’s kohina.txt which specifies how ppmtompeg packs the frames. Note that I just threw this together without too much thought, so it definitely needs tweaking depending on what the video is used for and so what (quality, compression, speed) matters. For example, I only used I-frames due to lack of imagination.

PATTERN IIIIIIII
OUTPUT kohina.mpeg
INPUT_DIR stdin
BASE_FILE_FORMAT PPM
INPUT_CONVERT *
GOP_SIZE 8
SLICES_PER_FRAME 30
PIXEL HALF
RANGE 2
PSEARCH_ALG LOGARITHMIC
BSEARCH_ALG SIMPLE
IQSCALE 1
PQSCALE 1
BQSCALE 1
REFERENCE_FRAME ORIGINAL

And here’s what it looks like, recompressed with Theora (using Oggconvert): kohina.ogg (2,8 MB). Generating an accompanyng soundtrack is trivial with Audacity.