{"@context":"http://iiif.io/api/presentation/3/context.json","id":"https://arsc.aviaryplatform.com/iiif/k93125s902/manifest","type":"Manifest","label":{"en":["Flutter: A Brief History of Time Distortion (and How to Measure \u0026 Mitigate It)"]},"logo":"https://d9jk7wjtjpu5g.cloudfront.net/organizations/logo_images/000/000/019/original/ARSC_Full_Logo_RGB_K.jpg?1605438091","metadata":[{"label":{"en":["Agent"]},"value":{"en":["John K. Chester (Presenter)","Brad McCoy (Chair)"]}},{"label":{"en":["Date"]},"value":{"en":["2025-05-15 (Created)"]}},{"label":{"en":["Format"]},"value":{"en":["Video","Audio","Slides"]}},{"label":{"en":["Description"]},"value":{"en":["\u003cp\u003ePrior to the advent of digital recording, audio was recorded on a moving mechanical medium: paper, cylinders, discs, film and tape. This presentation will concentrate on diagnosing and mitigating problems with film and tape transports. Ideally, the speed of the recording medium should be perfectly constant, both when recording and reproducing–but it never is. Mechanical problems cause repetitive speed variations. Rates below about 20 Hz (sometimes called wow) are perceived as pitch variations. Higher rates cause a variety of changes to the timbre and quality of an audio recording. I will survey flutter measurement standards and measurement systems, both analog and digital. All standards include a weighted measurement which includes only audible pitch variations. I'll show why this is of limited use in ranking quality of film and tape transports and not at all useful for diagnosing mechanical problems. Much more useful information can be obtained from examining the spectrum of the flutter. Finally, I'll discuss the Plangent Process, which digitally mitigates flutter in magnetic recordings. High quality analog magnetic recording requires mixing a high frequency bias signal with the audio. At tape speeds used for professional tape and film recording, the bias signal can usually be recovered with wideband playback electronics. The bias oscillator is always much more stable than the tape transports, so frequency variations of the recovered bias can be used to accurately measure and remove the combined flutter of the recorder and reproducer.\u003c/p\u003e"]}},{"label":{"en":["Publisher"]},"value":{"en":["Association for Recorded Sound Collections"]}},{"label":{"en":["Rights Statement"]},"value":{"en":["\u003cp\u003eCopyright Association for Recorded Sound Collections\u003c/p\u003e"]}},{"label":{"en":["Language"]},"value":{"en":["English"]}}],"summary":{"en":["\u003cp\u003ePrior to the advent of digital recording, audio was recorded on a moving mechanical medium: paper, cylinders, discs, film and tape. This presentation will concentrate on diagnosing and mitigating problems with film and tape transports. Ideally, the speed of the recording medium should be perfectly constant, both when recording and reproducing\u0026ndash;but it never is. Mechanical problems cause repetitive speed variations. Rates below about 20 Hz (sometimes called wow) are perceived as pitch variations. Higher rates cause a variety of changes to the timbre and quality of an audio recording. I will survey flutter measurement standards and measurement systems, both analog and digital. All standards include a weighted measurement which includes only audible pitch variations. I'll show why this is of limited use in ranking quality of film and tape transports and not at all useful for diagnosing mechanical problems. Much more useful information can be obtained from examining the spectrum of the flutter. Finally, I'll discuss the Plangent Process, which digitally mitigates flutter in magnetic recordings. High quality analog magnetic recording requires mixing a high frequency bias signal with the audio. At tape speeds used for professional tape and film recording, the bias signal can usually be recovered with wideband playback electronics. The bias oscillator is always much more stable than the tape transports, so frequency variations of the recovered bias can be used to accurately measure and remove the combined flutter of the recorder and reproducer.\u003c/p\u003e"]},"requiredStatement":{"label":{"en":["Attribution"]},"value":{"en":["\u003cp\u003eCopyright Association for Recorded Sound Collections\u003c/p\u003e"]}},"provider":[{"id":"https://arsc.aviaryplatform.com/aboutus","type":"Agent","label":{"en":["Association for Recorded Sound Collections"]},"homepage":[{"id":"https://arsc.aviaryplatform.com/","type":"Text","label":{"en":["Association for Recorded Sound Collections"]},"format":"text/html"}],"logo":[{"id":"https://d9jk7wjtjpu5g.cloudfront.net/organizations/logo_images/000/000/019/original/ARSC_Full_Logo_RGB_K.jpg?1605438091","type":"Image"}]}],"thumbnail":[{"id":"https://d9jk7wjtjpu5g.cloudfront.net/collection_resource_files/thumbnails/000/276/660/small/ARSC_conf_2025_Chester_thmb.jpg?1749550806","type":"Image","format":"image/jpeg"}],"items":[{"id":"https://arsc.aviaryplatform.com/collections/3300/collection_resources/148829/file/276660","type":"Canvas","label":{"en":["Media File 1 of 1 - ARSC_conf_2025_Chester_video_1.mp4"]},"duration":2063.209,"width":640,"height":360,"thumbnail":[{"id":"https://d9jk7wjtjpu5g.cloudfront.net/collection_resource_files/thumbnails/000/276/660/small/ARSC_conf_2025_Chester_thmb.jpg?1749550806","type":"Image","format":"image/jpeg"}],"items":[{"id":"https://arsc.aviaryplatform.com/collections/3300/collection_resources/148829/file/276660/content/1","type":"AnnotationPage","items":[{"id":"https://arsc.aviaryplatform.com/collections/3300/collection_resources/148829/file/276660/content/1/annotation/1","type":"Annotation","motivation":"painting","body":{"id":"https://aviary-p-arsc.s3.wasabisys.com/collection_resource_files/resource_files/000/276/660/original/ARSC_conf_2025_Chester_video_1.mp4?1749550706","type":"Video","format":"video/mp4","duration":2063.209,"width":640,"height":360},"target":"https://arsc.aviaryplatform.com/collections/3300/collection_resources/148829/file/276660","metadata":[]}]}],"annotations":[]}]}