Defining Digital Reciprocity Under Sampling

‘…its like looking at the ocean from above and seeing that every island is the tip of the mountain, part of a larger substructure that coheres beneath the surface.’ 1

The mechanics of the miniDV camera are integrally linked to the DRUS technique of image making by the way digital images are made with this device. This camera, is designed for use based on similar conceptual principles to the motion picture camera. It has multiple still frame exposures, and the digital image processing has a different methodology of capture, storage and retrieval of video data. This is what gives the unique look to the DRUS images.

Digital Reciprocity Under Sampling defines this technique for creating images. Digital refers to the original recorded medium, a series of 1s and 0s. Reciprocity refers to the fast forward and rewinding action necessary to distort the video imagery. Lastly, ‘under sampling’ refers to a process in which sampling of the digital data is undermined in the digital to analogue process. The fast forwarding or rewinding movements economises and edits picture elements on the videotape known as sampling functions. The sampling of pixels represents a process of change. In that process, some pixels will default to black, or pixels from the previous frame will remain.

Encoding                 

Encoding is made up of three processes. These take place before any information is transferred onto the videotape. Contained within the video camera’s relatively small housing is a system comprised of three components: a charge-coupled device (CCD), an analogue-to-digital converter (ADC or A/D converter) and a DV codec (compression/decompression rate device). Understanding these three components is necessary to understanding the process of DRUS.

The CCD is an optical scanning mechanism 2 that generates electrical current in proportion to light input. This allows the simultaneous capture of picture elements with multiple brief exposures. 3 As these picture elements are captured they are simultaneously stored for the ADC converter.

The ADC converter is a device or processor used for converting an analogue signal, which the CCD has stored, such as a voltage level or video signal. The ADC converter works with numerical 1s and 0s rather than voltage to create an image; hence, an image must be converted to numerical form before processing. This conversion process is called digitisation. The image is divided into small regions that are similar to silver halide grain in silver photography, called picture elements or pixels. Within each pixel are a number of discrete bits (short for binary digit) that determine the pixel’s value in terms of the intensity colour and luminance. 4 In addition to the characteristics within the two-dimensional space, the image is divided into horizontal lines made up of adjacent pixels. This common subdivision scheme is the ‘rectangular sampling grid’.

The final component, the DV codec, basically takes the digital data and compresses the pixel information to save storage space. This allows the information to pass faster, and requires less processing time. A compression method based in a ‘lossy codec’, this compression/decompression method device saves digital data files by removing non-critical data per second rather than per frame. Pictures are analysed looking for redundancy and repetition and so it discards unnecessary data. These techniques were primarily developed for digital transmission but have been adopted as a means of handling digital video in computers and reducing the storage demands for digital video tape recorders (VTRs). Digital video is a good editing codec because it doesn't assign frames of video with partial information known as ‘inter-frame compression’, but rather each frame of video contains all of its information. Thus, every frame is known as a keyframe. 5 Any adjustment to the video in the post-production editing stage will not cause degradation to the quality of the image.

Though these components of encoding – CCD, ADC converter and DV codec – generate the digital signal that is recorded onto the video tape, it doesn’t describe how those digital elements are manipulated.

Decoding

The configuration of the digital data on the videotape describes the initial three stages in the framework for video signal, ‘source message/schemata’, ‘encoding’ and ‘conduit’. This ‘encoding’ section of the framework controls how the digital data is composed. However, it is in the process of ‘decoding’ the composition of the individual image frames that DRUS is generated.

For the ‘source message/schemata’ to be transferred to its ‘representational message/schemata’, in this case the video display, it must be ‘decoded’ from the digital video tape. This is the rearrangement of the digital data files into electric currents that transfer it from digital back to analogue information. This is represented in the moving image on a video display. However, due to the way in which that data is decoded, one is never aware of the elements that make up the data. It is only when the data is scanned in the fast forward or rewind function that one witnesses the scrambling of rectangular elements known as ‘blocks’. 6 These rectangular areas of picture, usually in two sizes of 8 x 8 pixels or 16 x 16 pixel macroblocks, are artefacts of compression that when subjected to rapid scanning are visible. Additionally, they are also sometimes visible in general viewing. 7 These are described as ‘misplaced blocks’ that show momentarily as a misplaced rectangular area of picture with distinct boundaries. The 8 x 8 pixel blocks are seen as one of the major defects of digital compression. Its visibility generally depends on the amount of compression used, the quality of the original signal, and the quality of the coder. The 16 x 16 pixel macroblocks are due to the failure of motion prediction/estimation in the encoder or other motion vector system, such as a standards converter. 8

The objective of the DRUS technique is to locate single frames of abstracted digital imagery. A system had to be developed to deliberately bring these blocks out of the digital video footage and hold them. Recording the digital video onto an analogue video deck created a way of playing back the previously recorded fast forwarding and rewinding actions of the digital video tape. The frames of the analogue video could be analysed one by one, and the appropriate level of image deconstruction could be selected.

A New Context and a New Process of Working:
The Origins of DRUS

With living in the new environmental setting and cultural context of Tokyo, I began working in mediums beyond emulsion-based photography. A job in an international secondary school focused my attention on video production. The facilities combined outdated analogue postproduction equipment, such as 3/4 inch U-matic tape decks, with miniDV cameras. This combination of outdated and cutting edge technology created an environment of experimentation and ingenuity. In the time spent viewing countless hours of videotape, I began to see frames, still moments of captured gestures, juxtapositions and distortions that I had not witnessed in the frame of my single lens reflex.

With miniDV footage shot in the city, I returned to the analogue editing suite and scanned randomly. Single images, frozen by the paused frame, captured the psychological spaces and emotional conditions of the inhabitants of Tokyo. But these were not merely clear frames of imagery, they were semi-complete assemblages of digital information indicating what was to come or what had already been, images caught in process, in flux. The miniDV camera, with its lightweight body and retractable Liquid Crystal Display (LCD) had generated an entirely different relationship between the body and instrument. This camera became an image-capturing device more akin to the actual physical and perceptual experience of moving through Tokyo.