Sustainability of Digital Formats: Planning for Library of Congress Collections
Sustainability of Digital Formats: Planning for Library of Congress Collections |
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| Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact | |
| Full name | AVI OpenDML with Motion JPEG Video |
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| Description | File format that wraps a series of JPEG images with other data chunks, e.g., audio, in AVI_OpenDML_1_02, to produce a moving image sequence, referred to as Motion JPEG (MJPEG). The images represent individual frames (or fields? Comments welcome) from a pre-existing video recording, generally analog. The images employ a form of the JPEG still image compression algorithm, as specified by AVI_OpenDML_1_02. Microsoft refers to this encoding as JPEG DIB (Device Independent Bitmap). See Notes for more information. |
| Production phase | Generally a middle-state or final-state format. |
| Relationship to other formats | |
| Subtype of | AVI_OpenDML_1_02, AVI File Format with OpenDML Extensions |
| Contains | MJPEG, MJPEG (Motion JPEG) Video Codec |
| May contain | WAVE, WAVE Audio File Format. For audio interleaved with video. |
| May contain | MP3_CBR, MP3, Constant Bit Rate. For audio interleaved with video |
| LC experience or existing holdings | |
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| LC preference | See AVI. |
| Disclosure | See AVI, AVI_OpenDML_1_02, and JPEG. |
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| Documentation | See AVI, AVI_OpenDML_1_02, and JPEG. |
| Adoption | AVI and AVI_OpenDML_1_2 are widely adopted for video production and filemaking; in 2000, the expert commentator John McGowan wrote, "Most PC video capture and editing systems capture video to AVI files using Motion JPEG video compression." |
| Licensing and patents | See AVI and AVI_OpenDML_1_02 |
| Transparency | See AVI, AVI_OpenDML_1_02, and MJPEG. |
| Self-documentation | See AVI and AVI_OpenDML_1_02 |
| External dependencies | See AVI and AVI_OpenDML_1_02 |
| Technical protection considerations | See AVI and AVI_OpenDML_1_02 |
| Moving Image | |
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| Normal rendering | Good support. |
| Clarity (high image resolution) | Moderate to very good, depending on the compression quality level applied. |
| Functionality beyond normal rendering | See AVI and AVI_OpenDML_1_02 |
| Tag | Value | Note |
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| Filename extension | avi |
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| Internet Media Type | See related format. | See AVI and AVI_OpenDML_1_02 |
| Magic numbers | See related format. | See AVI and AVI_OpenDML_1_02 |
| Microsoft FOURCC | MJPG |
See the archived version of the Microsoft registry of FOURCC and WAVE codes mounted by IANA. |
| General |
Avery Lee, writing in the rec.video.desktop newsgroup in 2001, commented that "MJPEG, or at least the MJPEG in AVIs having the MJPG fourcc, is restricted JPEG with a fixed -- and *omitted* -- Huffman table. The JPEG must be YCbCr colorspace, it must be 4:2:2, and it must use basic Huffman encoding, not arithmetic or progressive. . . . You can indeed extract the MJPEG frames and decode them with a regular JPEG decoder, but you have to prepend the DHT segment to them, or else the decoder won't have any idea how to decompress the data. The exact table necessary is given in the OpenDML spec." |
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| History |
OpenDML was initially developed in 1996-97 to support the carriage of MJPEG (Motion JPEG), with frames are encoded as JPEG-DIB (Device-Independent Bit compression). Subsequently, the "OpenDML extensions," as they are called, have come into wide use for video codecs, in large part because they permit the creation of the large files needed to carry video data at medium or high resolution. |
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