Acquiring Digital Video
- Physical Format Standards
- Digital Format Standards
- MP4 and QuickTime Benefits
- Distributing Digital Video
- Archival Recommendations
- File Extension Standards
Digital videos are obtained most commonly by one of three methods: conversion, use of a digital video camera or, by obtaining an existing video file. In all cases copyright law must be considered. Permission from owners and subjects may require a signed release form. Prior to recording campus events, a signed media release form must be obtained from presenters.
Creating your own digital videos involves numerous crucial technical decisions. Poor decisions can result in digital files that are inadequate for their intended uses. By anticipating the most demanding end-use before the video is created or digitized, it is possible to choose specifications that will result in satisfactory video quality without squandering resources such as time or network storage.
Conversion involves the use of both hardware interfaces and software to read an analog (or digital) file and translate it into the desired digital video file. Conversion is quite complicated both because there are many different analog formats, each requiring different hardware, and because of the various options and settings involved in the software "translation". Moreover, each piece of hardware and software will have its own settings and user interface. If your digital video collection will involve significant transfer from existing analog collections, it is highly recommended that you consult with IT.
Physical Format Standards
The miniDV format, because it both produces a high quality image and has been widely adopted by manufacturers and users of consumer-level video equipment, is the recommended video format for Bowdoin College students, faculty, and staff. The miniDV tape uses high density magnetic media to record digital video and audio tracks, with tape contents easily transferable either to a PC or to a Mac platform using an IEEE-1394 (Firewire) cable.
Bowdoin College Information Technology and the Library’s Language Media Center support miniDV playback and editing, and the Library’s Special Collections and Archives is able both to play miniDV tapes and to convert these tapes to other formats (e.g. DVD or VHS) for distribution or for classroom use.
Recommended Tape Length
MiniDV tapes, similar to previous digital and analog video formats, allow information to be recorded on a magnetic film that is bonded to a plastic tape base. As with earlier formats, the thickness of this film and plastic base varies with the length of the tape housed in the cassette, with longer tapes having a thinner magnetic coating and plastic base. Because the thinner magnetic coating on longer length tapes is more susceptible to wear from the record heads on miniDV cameras, and because the thinner plastic base on longer tapes is more susceptible to stretching and deformation from recording and playback, it is recommended that members of the Bowdoin community use only tapes 83 minutes and shorter (when recorded on a camera’s highest quality SP setting) to assure that recorded material is not damaged through repeated recording and playback. It is also recommended that new tapes be used whenever recording an event which is intended to be archived (see Archival recommendations below).
Recommended Audio Setting
To ensure better compatibility among miniDV playback devices, it is recommended that miniDV cameras have their audio set to 16 bits. Selection of higher bit depths can jeopardize audio playback on some machines.
Digital File Format Standards
These recommendations are based on established format protocols currently used to deploy media content to the Bowdoin Web site and other Web-based applications. I.e., Blackboard, e-Reserves, iTunes U, Podcasts, Bowdoin web site.
Recommended Media Containers
Bowdoin's baseline standard for both open and commercial software video formats is based on MPEG-4 Part 14. MPEG-4 Part 14 is a multimedia container format standard specified as a part of MPEG-4. It is most commonly used to store digital audio and digital video data, especially those defined by MPEG, but can also be used to store other data such as subtitles and still images. Additionally, MPEG-4 Part 14 also allows streaming over the Internet and is compatible with current server hardware installed at Bowdoin. The official filename extension for MPEG-4 Part 14 files is .mp4, thus the container format is typically referred to as MP4. The only exception to Bowdoin's baseline standard for an open audio format is MPEG-1 Audio Layer 3, more commonly referred to as MP3. MP3 audio is used to guarantee successful delivery of digital audio to the widest variety of computer platforms and mobile devices, such as MP3 players, iPods and cellular phones. To determine which media container to use, please consult with IT.
Recommended Software Platform
Quicktime is the recommended software platform for encoding and decoding of media content, but other encoders are freely and openly available to encode media into the recommended containers. Additionally, Quicktime is freely available to the public for both PC and Macintosh computer platforms and is currently the most used encoding engine for mobile video and audio devices (such asiPods). Quicktime also allows Bowdoin to leverage server side solutions, such as Apple's Podcast Producer, to automate the encoding, and deployment of media content in support of web related applications.
MP4 and QuickTime Benefits
The primary reason behind the selection of Quicktime as the recommended software platform is because both the MOV and MP4 containers can use the same MPEG-4 codecs, and are mostly interchangeable in a QuickTime-only environment. However, MP4, being an international standard, has more open support. This is especially true on most hardware devices.
Additionally, QuickTime's MPEG-4 Export dialog contains an option called "Passthrough" which allows a clean export to MP4 without affecting the audio or video streams. One recent discrepancy ushered in by QuickTime version 7 is that the MOV file format now supports multichannel audio while QuickTime's support for audio in the MP4 container is limited to stereo. Therefore multichannel audio must be re-encoded during MP4 export.
Distributing Digital Video
MiniDV is not suitable media to be used for distribution. Like its predecessors, miniDV tape is recorded on by a set of record heads inside the camera that magnetically encode digital information. Not all camera manufacturers use the same tracking settings to encode information to the tape, however, and it is possible that video shot on one model or brand of miniDV camera may not play back on different equipment. These tracking problems can be compounded by tapes which have been stretched through repeated use, and unlike analog videotapes, whose contents may still be viewable despite tracking problems, miniDV tapes are unforgiving, with slight tracking errors often rendering images unviewable. In addition, there are user-selectable camera settings – most notably audio bit depth – which can affect playback when using different miniDV devices. Consequently, users of miniDV video equipment should never assume that a tape they produce will be viewable on other people’s equipment. When distributing video shot on miniDV tape alternative formats, such as DVD or as a computer file (see recommendations below), are recommended.
Although miniDV tapes are the preferred format for capturing video images, this technology is not ideally suited to archival preservation. Magnetic media is inherently unstable and will, over time, begin to decay, thereby compromising the integrity of the source material. In addition, given the “all or nothing” nature of digital recording – data is either readable or it is not – relatively minor tape decay or deformation caused by repeated use can render miniDV tapes unviewable. This is unlike analog tape recordings, which may exhibit image distortions (e.g. static, color loss, or loss of tracking) when the tape has begun to decay or has been deformed, but, depending on the severity of the distortions, still allow the possibility of viewing damaged source material.
In order to minimize the risk that video of an event is lost due to decay or damage of the miniDV master tape, members of the Bowdoin community are recommended to preserve digital media in more than one format. A DVD can be used as a short term back-up for a miniDV master, but because DVDs are created using a compression algorithm, which produces video of diminished quality from the original, and because DVDs are prone to “bronzing” as the inner foil is exposed to air and playback is compromised, DVDs should not be used as the primary archival storage media. It is recommended that in addition to the miniDV master, a computer file of the video also be maintained (see recommendations below).
File Extension Standards
MPEG-4 (.mp4, .m4a, .m4b)
MPEG-4 audio and video files generally use the standard .mp4 extension. Audio only MPEG-4 files typically use the standard .m4a extension. Digital audiobooks are typically use the .m4b extensions
MPEG-1 Audio Layer 3 (.mp3)
MPEG-1 Audio Layer 3 audio files use the .mp3 extension.
Download-able Video (.mov)
Video purposed for download on the Bowdoin web site and related web applications should make use of Quicktime and the .mov extension to offer the best possibility of successful playback.
Streaming Video (.mov)
Video purposed for streaming playback on the Bowdoin web site and related web applications should make use of Quicktime and the .mov extension to offer the best possibility of successful playback.
Streaming Audio (.mp4)
Audio purposed for streaming playback on the Bowdoin web site and related web applications should make use of Quicktime and the .mov extension to offer the best possibility of successful playback.
Mobile Video (.m4v)
Video purposed for download and viewing on mobile devices (Such as iPods and iPhones) should make use of Quicktime and the .m4v extension to offer the best possibility of successful playback.
Mobile Audio (.mp3)
Audio purposed for download and listening on mobile devices should use the .mp3 extension to offer the best possibility of successful playback.