Master WAVE (wav.) files were created at a sampling rate of 96,000 samples per second, 24-bit word length, and a single (mono) channel. The master files, due to their large size, are not included in the Web presentation but may be accessed in the American Folklife Center’s Reading Room.
Three derivative copies of each master file are included in the online presentation. They include WAVE files created at a sampling rate of 44,100 samples per second and 16-bit word length as well as MP3 and RealAudio files created at a constant bit rate of 256 kilobits per second and a sampling rate of 44,100 samples per second.
Surface noise, abrupt starts or ends, and distortion are inherent in the original tapes. These recordings have not been restored and are presented as is to allow for maximum playback flexibility. Some of the recordings, however, were modified to remove interviewee or interviewer addresses or telephone numbers.
Video files are presented in three formats. MPEG-1 files were created with an image size of 352x240 pixels, frame rate of 29.97 fps, and target data rate of approximately 1 megabits/second. QuickTime files were produced with an image size of 320x240 pixels and target data rate of about 230 kilobits per second. RealMedia files have a video size of 352x236 pixels with a data rate of 450 kilobits per second.
Background noise, abrupt starts and ends, and inconsistent video and audio levels are inherent in the original recordings and are presented without modification.
Photographs and drawings were scanned on site at the Library of Congress Information Technology Services (ITS) scan lab using overhead digital cameras with Phase I software and were post-processed using Adobe Photoshop software. Images were scanned in either grayscale or color mode, depending upon the original, at 300 ppi and saved in the uncompressed TIFF file format. Three service images were also created: a compressed reference image in the JPEG format, averaging 1,024 pixels on the long side of the image with a compression rate of 8:1; a high-resolution compressed display image in the JPEG format, averaging 640 pixels on the long side of the image with a compression rate of 15:1; and a thumbnail GIF image averaging 150 pixels on the long side of the image.
Some of the images used in this presentation were received in JPEG format. For images which are 1,024 pixels on the long side, two derivatives were created; a high-resolution compressed display image in the JPEG format, approximating 640 pixels on the long side of the image with a compression rate of 15:1 and a thumbnail GIF image averaging 150 pixels on the long side of the image. For images received with 640 or fewer pixels on the long side, only a thumbnail GIF was made.
Project staff used Optical Character Recognition (OCR) software to create text from TIFF files. The resulting texts were manually corrected and marked up in SGML in compliance with the American Memory Document Type Definition (DTD). Grammatical or spelling errors in the source material have not been edited.