Digitizing the Collection
Most of the early films included in American Memory were taken from the Library's Paper Print Collection of more than 3000 titles. When they were deposited for copyright from 1894-1912, these films were printed as positive pictures frame by frame on long rolls of paper. In recent years, in order to serve the goals of access and preservation, the Library of Congress has been copying the paper rolls onto 35mm motion picture negative film. Next, a positive film print is made from the 35mm negative and this is transferred to Betacam SP videotape to produce the master for digitization. In order to present an authentic record of the paper prints as artifacts, some of the edging and perforations evident on the originals have been left in the digital frame. Likewise, original labels, titles, and other tagging documentation has been retained, as well as other imperfections.
The motion pictures chosen for digitization were all black-and-white and silent, whether originating from the paper prints or from early film copies in other collections. The original motion pictures were shot with hand cranked cameras at varying frame rates, generally at 16 frames per second (fps). (In fact, the frame rate may vary within a single title.) In the video mastering process, the playback speeds were adjusted to present the appearance of natural motion to the greatest degree possible.
The MPEG and Quicktime versions of titles with running times greater than four minutes have been divided into segments to reduce the file sizes to 40MB or less. A typical 28.8 internet connection achieves a theoretical maximum download rate of approximately 3.5 KB/sec (210 K/min) under ideal conditions. Therefore, a file of 40 MB would take approximately 190 minutes (3 hours 10 minutes) in optimal conditions and more likely much longer than that (up to 2 to 3 times depending on internet traffic load).
The majority of sound recordings included in American Memory were taken from cylinder and disc recordings in the Library's collections. The analog audio from the cylinders and discs were transferred to Digital Audio Tape (DAT) to produce a master source for digitization. Some surface noise and scratching may be apparent on the recordings since they have not been enhanced or altered in any way from their original state. WAVE and RealAudio versions have been supplied for each recording.
Due to the limited audio quality (bandwidth capability) of the cylinders and discs, the WAVE files were created from the DAT tape at 22Khz, 16-bits, and a single mono channel.