Be aware, however, that the logical format (UDF, FAT, HFS etc.) as well as any defect management system employed consume space otherwise available for user information. For example, DVD-RAM can dedicate as much as 184 MB (192,937,984 bytes) on a 1.46 GB disc, 126.86 MB (133,022,816 bytes) on a 2.6 GB disc and 216 MB (226,492,416 bytes) on a 4.7 GB disc for defect management while Mount Rainier formatted DVD+RW (DVD+MRW) can allocate up to 128.75 MB (135,000,000 bytes) on a 1.46 GB disc and 515.94 MB (541,000,000 bytes) on a 4.7 GB disc.
How many minutes of video can be stored on writable DVD discs?
In contrast to CD technology where Red Book audio or Video CD specifications rigidly prescribe the amount, type and quality of material a disc contains, the DVD-Video format is flexible, permitting content to be housed in different forms and levels of quality. Consequently, the number of minutes of audio and video that can be stored on a writable DVD disc varies considerably.
In terms of its basic capabilities, the DVD-Video format supports one main stream of video (MPEG-1, MPEG-2) with up to nine separate camera angles, as many as eight streams of audio (Dolby Digital, MPEG-1, MPEG-2, LPCM, DTS, SDDS), a maximum of 32 subpicture streams (graphic overlay) as well as navigation menus and other extras. Each of these occupy space so the amount of material that can be recorded depends upon the number of features incorporated, the type and degree of audio and video compression used and the capacity of the disc. For example, a single-sided 4.7 GB disc holds roughly one hour of straightforward audio and video at maximum DVD quality and a 1.46 GB disc approximately 18 minutes. At the other end of the spectrum, the same discs might accommodate as much as nine hours and three hours respectively of VHS quality material.
Not all computer video and audio encoding systems, authoring software and consumer electronics (CE) recorders offer access to all DVD-Video features or support all degrees of compression. Thus, in practice, different products offer a range of possible recording times. For example, an entry-level DVD-Video authoring software package might support only limited features and permit only one hour of recording (using as little compression as possible) to keep the quality of the final result as high as possible. Mid-range and professional hardware and software tools provide the greatest degree of freedom while consumer products generally offer the least.
Generally speaking, consumer electronics (CE) recorders have a variety of automatic or manual recording modes typically ranging from one to four hours (occasionally six to eight hours) per 4.7 GB disc while writable DVD camcorders usually offer between 20 minutes to one hour per 1.46 GB disc. Although manufacturers sometimes use language such as High Quality (HQ), Standard Play (SP), Long Play (LP) and others to describe the recording time of their products, be aware that there are no broadly accepted industry standards for the use of such terminology.