imaging/getting-started-with-image-streams.md

@@ -192,6 +192,37 @@ It would look as following (press ctrl-c, when you want to stop):
 
 Depending on your desired video quality, frame rate, compression, etc, you might need to change the command line parameters of **ffmpeg**. Sometimes it's not easy, but there is a lot of **ffmpeg** online documentation, Q&A, recipes, etc.
 
+## cv-cat log: image stream logging
+One **cv-cat** filter worth mentioning is **log**. E.g. if you want to log your camera feed in the current directory, you could run for some 20 seconds and then press **ctrl-c**:
+```
+> cv-cat --camera "log=.,period:10;null"
+```
+You will see in your current directory a couple of files named as something like:
+```
+> ls
+20201121T110413.284712.bin  20201121T110423.380330.bin
+```
+Each file will contain 10 seconds-worth image data starting from the time as in the file name.
+
+Further, try to run for some 20 seconds and then press **ctrl-c**:
+```
+> cv-cat --camera "log=.,period:10,index;null"
+> ls
+20201121T110831.643421.bin  20201121T110841.736154.bin  index.bin
+> cat index.bin | csv-from-bin t,uw,ul | head -n4
+20201121T110831.643421,0,0
+20201121T110831.687222,0,921620
+20201121T110831.757203,0,1843240
+20201121T110831.826652,0,2764860
+```
+**index.bin** allows conveniently search specific frames or frame ranges in the log files. For each logged frame, the **index.bin** file record contains frame timestamp, number of the log file in which it can be found and offset from the beginning of the file in bytes.
+
+For more logging options, see **cv-cat --help --verbose**; look for **log=**.
+
+**snark** has other camera data acquisition utilities like **fire-cat** for firewire cameras. They comply with **snark** image format. Or you can write your own camera data acquisition utility. If your utility outputs raw image data or implements **snark** image data format, it can be seamlessly used with **cv-cat** and other **snark** image utilitities.
+
+It writes image stream into files based on 
+
 # **cv-calc**: more image manipulations
 **cv-cat** essentially deals with image filter pipelines, i.e. for each input image there is exactly one output image.
 
@@ -199,13 +230,11 @@ Depending on your desired video quality, frame rate, compression, etc, you might
 
 **cv-calc** has operations for cropping, regions of interest, primitive drawing, equirectangular map generation, striding, thinning, etc.
 
-See **cv-calc --help --verbose** for details and meanwhile try **cv-calc life** which runs a generalised version of [game of life](https://en.wikipedia.org/wiki/Conway%27s_Game_of_Life) on an arbitrary seed image.
+See **cv-calc --help --verbose** for details and meanwhile try for fun **cv-calc life** which runs a generalised version of [game of life](https://en.wikipedia.org/wiki/Conway%27s_Game_of_Life) on an arbitrary seed image.
 
 ```
 > cv-cat --file cat.jpg "resize=64,64" | cv-calc life --procreation 3 --stability 5.255 --step 0.02 | cv-cat "invert;resize=512,512,lanczos4;count;view;null"
 ```
-## logging
-todo
 
 # converting images from/to csv
 ## image-from-csv