General comments on digital reproductions of motion pictures
for American Memory
The motion pictures available in the American Memory collections are
all early silent movies. They include actuality films and entertainment.
Most were deposited through the Copyright Office as paper print rolls.
Digital formats for motion
The Library of Congress does not yet make computer-based digital
recordings of motion pictures for archival purposes. The conversion
process for these motion pictures involves several steps. First, they are
transferred to 35mm film from the paper prints or other media, where
necessary. The film is then converted to BetaCam-SP videotape, with
speed- correction to allow for 30 frame-per-second playback although the
original films were hand- cranked at an average 15-16 frames per second.
This videotape is edited to add character-generated titles. Finally, the
edited videotape is sampled twice to generate the digital versions.
Motion pictures that are more than four minutes long are divided into
For the serious user with more powerful equipment, an MPEG-1 version
is created at 30 frames per second and at a spatial resolution (size) of
320x240 pixels (at a data rate of approximately 1.2 Mbits per second of
playing time). For service to a wider range of users, a QuickTime version
is created at 10-15 frames per second and a size of 160x120 pixels (at a
data rate of approximately 640 Kbits per second, usually quoted as 80
Kbytes/sec, of playing time). In the future, the Library expects to
create and serve a streaming video version.
To provide a "thumbnail" preview of each video, the Library picks two
or three representative images and combines them in a GIF image.
For each movie, an item-level MARC record is available. In an 856
field, the combination of subfields $d and $f provides unique identifiers
for the associated digital reproductions. Files representing the motion
pictures are available in a directory structure (known at the Library of
Congress as an "aggregate") for which $d identifies the root.
Filenames for the different digital versions and segments of a motion
picture are created by combining the $f value (which identifies the item)
with distinguishing suffixes and file extensions.