Video Encoding at 5 bytes/frame

Bad Apple on 32K EEPROM

This is part two of a two-part series. Read part one here.

In this post we use Python to encode the full Bad Apple video (3m39s) into 32 kilobytes. Our playback hardware has no CPU so our video “compression” is limited to the features of our HD44780-powered LCD display.

We create an illusion of a full bitmap display by carefully juggling 8 CGRAM characters across the 8 x 4 video area and lean on LCD display persistence.

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Bad Apple on 32K EEPROM

Bad Apple on 32K EEPROM

This is part one of a two-part series. Read part two here.

This post covers how we interface a 32K EEPROM, a clock and an address register to a 20 x 4 LCD character display module and use it to play a video. We “decompress” the video by expanding our 8-bit data stream to 9 bits for playback in hardware. There is no CPU or microcontroller involved.

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Repeating Subfields and Multiple Text with ckanext-scheming

ckanext-scheming 2.1 now support Datasets with repeating subfields and repeating text fields. Repeating subfieds support custom snippets and validation just like regular fields.

This work is inspired by the excellent ckanext-composite extension and replaces ckanext-repeating repeating_text fields.

You must be using CKAN 2.8 or later and a custom IPackageController plugin to index datasets with repeating subfields.

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Faster datastore_search in CKAN

CKAN’s datastore_search now comes with format options and is up to 17x faster.

This article covers:

  • new total row calculation
  • new result generation
  • new record formats

datastore_search Performance Improvements

TL;DR:

  1. Use CKAN 2.7 or later and resource views and other code that uses datastore_search is faster with no other changes required
  2. Update your datastore_search client code to use one of the new records_format=csv and/or include_total=false options to make it much, much faster
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