Film and Video Study Materials with particular reference to Digital Video and DVD
Produced by Malcolm Le Grice and Steven Ball for the AHRB Centre for British Film and Television Studies.

1. Background

In conducting this limited research project we have concentrated on the practical issues of producing study materials on DV (Digital Video) including DVD (playable digital video on disc), and in passing touching on technical issues concerning compression coding systems and the longevity of DV or DVD as an ARCHIVAL material.

The main issue that drove this research was finding the best available system for providing film and video study materials. Best implied the highest quality achievable within the constraints of economical production and economical storage.

2. Archival Masters

'Archival masters' is not here defined in the sense that would be understood by Film and Video archivists, but in a way that applies to a Study Collection needing good quality, reliable 'masters' from which to make study copies.

The best available system for retaining high quality copies as archival masters is almost certainly Digital BETACAM. Equipment and tape for this system is very expensive and the tapes are too large for practical storage. Therefore this is not a cost effective system for producing and storing archival masters (or study copies) for a small collection.

After Digital BETACAM, two other systems provide very good high quality archival masters. BETACAM SP for many years a broadcast standard, remains a robust and high quality storage medium. It is still the most commonly used video system for most archival purposes (some archivists consider Digital BETACAM to be too recent a development to have confidence in its longevity). With the ‘coming of age’ of digital video, analogue video equipment has become more reasonably priced and there are many good used BETACAM SP recorders available. Professional servicing is still readily available for this equipment. However the tape costs remain high (approximately £15 per hour) and like Digital BETACAM they are too large for storage as a study material.

The second alternative tape system providing high quality archival masters is DIGITAL VIDEO. This is available in three cassette formats: DV (standardized), DVCAM (Sony proprietary) and DVCPRO (Panasonic proprietary). DVCAM and DVPRO are considered to be professional versions of the system and run at higher tape speeds in a variety of cassette sizes.

Mini DV could also be considered an option for archival masters. It uses a lower tape speed and the smallest cassette size. It is marketed as a domestic video format while offering identical image and sound quality to the professional digital video. MiniDV equipment costs are lower, however it should be noted that it is produced to less exacting standards than the professional formats.

A domestic MiniDV camera can normally be used as both a record and a replay machine, and it will often have both digital and analogue input and output. The tapes are very small and inexpensive (lowest costs are about £3.20 per hour).

The practical disadvantage with the MiniDV system for archival mastering is that both equipment and recorded tapes are less reliable and robust than DVCAM and DVCPRO. There are also variations within the format between recorders/cameras and between different brands of tape, that can often cause some image break-up when tapes made on one machine are played on another.

DIGITAL 8 is another domestic digital video format with image and sound quality technically identical to the other digital cassette formats.

DVD could be considered as both an archival mastering system and study copy medium. However, the MPEG2 compression format (see below) used in DVD retains less precise picture information and so is more appropriate for study than archival use. However the simplicity of retaining copying masters on DVD might make this an attractive option.

Formats such as VHS, SVHS, UMatic, Video8 or Video Hi8 do not provide high enough quality for use as archival masters.

3. Study Formats

VHS remains a viable study format, however in comparison with MiniDV, DVCAM and DVD the picture and sound quality remains poor and the storage size is less economical.

Mini DV or DVCAM provide very high quality digital picture and sound. They are small, easily stored and transported by post if necessary. MiniDV however is less durable and susceptible to dropouts likely to impede its viewability after a number of playbacks.

DVD provides high quality image and sound (only slightly below Mini DV or DVCAM but substantially better than VHS) and is very economical to store and transport. DVD is also efficacious for non-linear access to indexed points in a video programme.

3.1 Basic Technical Information: DVC and DVD
The digital encoding of the video signal is identical in each of the DIGITAL VIDEO cassette formats (DV, DVCAM and DVPRO) and as a result the sound and image is of the same high quality across the system. The main difference between them is the range of cassette sizes available (mini, standard and large), differences in tape speed and track pitch (the angle of the tape head). The higher tape speed and track pitch of the ‘professional’ formats allows more room for the digital video signal, and as a consequence these are less sensitive to the effects of physical degradation or damage than the ‘domestic’ MiniDV. format with its slower tape speed and a lower track pitch. MiniDV records approximately 60 minutes, 80 minutes in Long Play mode. Although developed for the consumer market the Mini DV format is now frequently used for broadcast material. The professional formats are mostly able to play MiniDV tapes (some MiniDV machines and camcorders, particularly those manufactured by Sony, will also playback DVCAM format tapes).

DIGITAL 8 is a digital development of the Video8/Hi8 analogue video systems, using 8mm tape in cassettes that are slightly larger than the MiniDV format. Like MiniDV DIGITAL8 was developed primarily for the consumer market. It uses the same encoding as the other digital video cassette formats while the tape speed and track pitch are higher than miniDV, technically comparable to DVCAM. It could be a more reliable format than MiniDV.

For copying from tape-to-tape, or playing back through a video monitor, the output from MiniDV or DVCam can be in the form of Composite Video (as with VHS or original Video8), S-video (as with SVHS or Hi8), or at the highest quality directly as a digital signal through Firewire (also known as i.LINK or IEEE 1394). Digital video transfer to computer is most commonly made via an internal fire-wire connection which is encoded by the digital video software. Some computer video-cards also provide for Composite Video or S-video input allowing digital computer files to be made directly from a signal originating from analogue video formats such as VHS, UMatic or Betacam SP. If the computer will only receive a Firewire input then any transfer from analogue video would require this first to be dubbed to a digital video cassette format before being transferred, or via a ‘bridge’ converter unit that will take a composite or S-video analogue input signal to a Firewire output.

3.2 Digital Video files on the Computer
There is a range of possible file formats for recording video on the computer such as QuickTime, AVI or MPEG. These digital video computer code files store the image and sound information on the Hard Disc of the computer. In their raw uncompressed state there is no loss of quality from the original DV Cassette, and video can be recorded back to DV Cassette without deterioration in image or sound. All editing of video on the computer is performed using digital video files, however these files are only relatively standard in format; there are minor differences in form and not all software is able to read all types of DV file. This is not normally a problem if only one software package is being used for capturing and editing. It is also possible to use certain digital video editing software, and stand alone conversion software to convert files between formats.

Digital video files take up a large amount of disk space. As a rule of thumb 1 hour of full resolution video requires 12 Gigabytes. The different file formats often use different CODECs (Compression/Decompression algorithms) that reduce the file size for particular types of storage and delivery.

MPEG2 is a digital video CODEC that represents a form of compression that balances audio/visual quality with the need for storing large amounts of data. As a rule of thumb 1 hour of an MPEG2 file requires a little under 5 Gigabytes. It thus requires approximately half the Hard Disc space of the same material stored as uncompressed files but with some loss of detailed resolution. MPEG2 is the current standard form of compression and storage for DVD.

The MPEG1 compression system provides an image quality approximately equivalent to VHS resolution. MPEG1 produces files small enough to be played from normal CD discs (see SVCD below) where MPEG2 requires DVD.

3.3 DVD as a Study Format
DVD stands for Digital Video Disc or Digital Versatile Disc. The second designation simply indicates that these discs can be used to record and store large quantities (4.7 Gigabytes) of any form of computer data, as well as the particular system used for video replay.

In the context of recording video on DVD, a MAJOR problem can derive from the fact that there are four different kinds of recordable DVD discs, and four formats of DVD writers (burners, recorders) available for computers. These disc and writer (burner) formats are as follows DVD+R, DVD+RW, DVD-R and DVD-RW. The R simply means recordable once only, and RW means that the disc can be re-recorded a number of times. More important is the designation + or - (plus or minus) which indicates whether the disc is read from the centre to the edge or vice-versa. This is particularly significant as the discs chosen must match the DVD writer (burner) being used on the computer to record the disc. It is advisable that the DVD writer chosen for the computer is capable of recording all four types of disc. This will be designated on the hardware as suitable for DVD+R, DVD+RW, DVD-R, DVD-RW. Pioneer make such a writer currently type number DVR-AO6 at about £220.

SVCD is a format offering VHS quality image and sound on a low cost 700-800 Megabyte CD disc. SVCD copies (MPEG1) can be ‘burned’ and replayed through rewritable CD drives now available on most PC’s at lower cost than DVD production. However not all DVD players will accept the SVCD format so its use can be uncertain. The image quality of SVCD is significantly less that MPEG2 based DVD.

3.4 DVD Players and Recorders
Again there are variations in the DVD standards accepted by different domestic DVD players. All indications are that DVD- (DVD minus) is likely to be a more common standard than DVD+ (though some machines seem able to play both).

Most recent PC’s have DVD replay facilities and some are supplied with DVD writers. However there is no certainty that the supplied DVD writer will produce DVD’s suitable for all domestic DVD players. (Thus the desirability of fitting a DVD writer capable of writing and reading all forms of disc).

Recent developments in domestic DVD recorders (such as those produced by Philips and Panasonic), introduces the possibility of making high quality recordings from analogue sources (VHS, UMatic, Betacam SP, etc) or via a digital link from computer or digital video player or camcorder. The recordings are made in real time, and can be edited and indexed before the discs are finalised. The recorded discs are DVD- format and therefore compatible with the majority of DVD players. The Philips DVDR75 recorder is currently available for under £400.

4. Film and Video Study On-Line
Digitalisation of film and video makes it intrinsically suitable for electronic transmission on-line. However there are practical constraints that must be considered in developing or using such systems. There is a crucial relationship between: the size of the file, the bandwidth of the on-line system, and the acceptable image and sound quality. Smaller digital video file sizes allow for faster downloading. The smaller size is often achieved by a combination of a reduction in frame size, frame per second playback, and audio sampling rate with a high level of compression. This results in poor audio-visual quality. This level of compression is most commonly used for QuickTime format or streaming Real Media files suitable for delivery over the internet.

At this time, video streaming using low compression rates has a limited application for on-line broadband, but would not be suitable for the more common modem-based, dial-up internet access. In this case only highly compressed files with much greater loss of quality are feasible.

5. Conclusions

These conclusions are specifically directed towards the needs of Study Collections. It assumes that their purpose is to improve and broaden access to film and video study materials offering the best possible quality within economic constraints. It is not directed towards Archiving or Preservation. The term ‘archival mastering’ is used here to imply high quality and robust mastering copies from which the study copies may be made and renewed as necessary.

5.1 Masters
As smaller study collections are unlikely to be able to produce and maintain archival masters on DIGITAL BETACAM then DVCAM provides the most robust system at a reasonable price for hardware and tape. MiniDV is a feasible option, but there are instabilities that should be borne in mind. Digital8 is by far the cheapest and would appear to be the more technically robust of the domestic digital tape formats. However its future is seriously in doubt as it is not compatible with any other format, whereas miniDV having gained a foothold in low budget professional and broadcast as well as at consumer level is assured a relatively secure future.

The convenience of DVD, despite its slightly lower quality should not be dismissed.

5.2 Study Copies
MiniDV and DVCAM produce high quality sound and video image and are viable study formats, however both are susceptible to degrees of physical wear and tear, resulting in image degradation restricting their usability over time.

DVD provides very good image and sound quality combined with economical and robust hardware and storage medium. Unlike tape based formats, it has the added potential advantage of flexible searching without stress and wear. Replay hardware is cheaply available and it has already become an international domestic replay system.

5.3 Making DVD Copies
The expected process would be to copy (capture) image and sound from an archival master (such as DVCAM) to the computer hard disc as an MPEG2 file and then to ‘burn’ compilation discs on DVD. However, the recent introduction of high quality domestic DVD recorders, replacing VHS video recording, offers the possibility of recording directly from the master to DVD.

5.4 On-line Formats
It must be assumed that on-line systems do not currently offer sufficiently high visual and sound quality to have any value to serious study and research. Only MPEG2 video over a broad-band connection would seem close to being feasible for on-line study.

6. Recommendations

VHS video tape is a well established viewing system, it is economically viable and robust but represents only the most basic acceptable sound and image quality. DVD has already become established as a high quality presentation system and combines good audio-visual quality with a low cost in a very robust playback medium. The aim should be to make as much of a collection as possible available on DVD. There are added advantages to this policy. The MPEG2 format can be easily encoded for online streaming on-line, and for presentation direct from hard disk as used by David Curtis and Illuminations in the Tate Britain ‘A Century of Artist’s Film in Britain’.

There remains some uncertainty regarding the long-term feasibility of archival mastering on hard disc using MPEG2. The computer storage capacity needed would be very high and the discs themselves and this form of digital storage are currently more vulnerable to complete loss of information than tape. A possibility worth investigating would be for DVD to be used for back-up storage of video data files where regular cloning is an option.

Study collections should seek to hold highest possible quality masters at the lowest cost. The most suitable current system would be DVCAM. The MiniDV format offers comparable quality at a cheaper price, but being less durable would only be suitable where the tape material is not likely to be played with any regularity.