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The consumer-oriented DV uses 10 micron tracks in SP recording mode. Newer camcorders offer an LP mode to increase recording times, but the 6.7 micron tracks make tape interchange problematic on DV machines, and prevents LP tapes from being played in DVCAM or DVCPRO VTRs. Sony's DVCAM professional format increases the track pitch to 15 microns (at the loss of recording time) to improve tape interchange and increase the robustness and reliability of insert editing. Panasonic's DVCPRO increases track pitch and width to 18 microns, and uses a metal particle tape for better durability. DVCPRO also adds a longitudinal analog audio cue track and a control track to improve editing performance and user-friendliness in linear editing operations.
 

Digital8?
Sony's Digital8 uses DV compression atop the existing Video8/Hi8 technological base. Digital8 records on Video8 or Hi8 tapes, but these run at twice their normal speed and thus hold half the time listed on the label. Digital8 will also play back existing Video8 and Hi8 tapes, even over 1394/i.link, allowing such tapes to be read into NLEs (at least, those for which the lack of timecode is not an issue -- batch capture utilities are unlikely to work, since Video8/Hi8 timecodes are not sent across the 1394 connection).

Digital8 is a camcorder-only format as of Spring 1999; no VTRs are expected. It appears to be the 8mm division's way of keeping its customer base from defecting to DV. By leveraging the massive investments of 15 years in 8mm analog camcorders and transports, the unit cost of Digital8 gear is kept very low, roughly half of what a comparable DV camcorder would cost, and its ability to play back legacy analog tapes is worthwhile for those with large libraries of 8mm.

All Digital8 camcorders can record from the analog inputs (at least outside the EU), and all are equipped with i.LINK ports for digital dubbing and NLE connections.

What is 1394 and/or "FireWire"?
IEEE-1394 is a standard communications protocol for high-speed, short-distance data transfer. It has been developed from Apple Computer's original "FireWire" proposal (FireWire is a trademark of Apple Computer). Check out the white papers on Adaptec's website for pointers to additional 1394 sites for detailed information.

Sony calls their implementation of 1394 "i.LINK".
 

Why are DV and 1394 always discussed together?
They appear to have been developed together. The data stored on DV tape appear to reflect the packet structure sent across a 1394 link to a frightening degree of exactness. Certainly the DV format and 1394 High Performance Data Bus co-evolved, such that the first consumer DV camcorder in the USA (the Sony DCR-VX1000 and its single-chip brother the VX700) was also the first 1394-equipped consumer product available.
 

What does a 1394 connection do for me?
Plenty of good things:

• You can make digital dubs between two camcorders or VTRs using 1394 I/O, and the copy will be identical to the original.
• You can do cuts-only linear editing over 1394, with no generation loss.
• You can stick a 1394 board into your computer (PC or Mac), and transfer DV to and from your hard disk. If your system can support 3.6 MBytes/sec sustained data rate -- simple enough with many A/V rated SCSI-2 drives and with most ATA/EIDE drives these days -- the world of computer-based nonlinear editing is open to you without paying the quality price of heavy JPEG compression and its associated artifacts, or the monetary price of buying heavy-duty NLE hardware and banks of RAID-striped hard drives.

Some time ago I edited a friend's wedding, going from Hi8 camera originals to a DV edit master. The 20-minute ceremony was covered by two cameras; we sync-rolled the VTRs and mixed the show in real time as if it were live. At the end, we weren't sure we liked it. So we dubbed it off via 1394 to another DV cassette, inserted a fresh DV cassette, and had another bash at the edit. This time, we liked it. We put the tape into the VX1000 and set up the DHR-1000 VTR as the recorder, using the built-in editor to drop the second attempt in frame-accurately atop the first across the 1394 wire. No generation loss. And we still had the first edit on the backup tape, should we have changed our minds.
 

Is 1394 that much better than Y/C or component analog?
Yes. A 1394 dub is a digital copy. It's identical to the original. That's really nice.

Yes, you can do almost the same thing with a SMPTE 259M SDI (serial digital interface) transfer. But VTRs with SDI cost big money. 1394 is built into many low-end cameras and VTRs, and the connecting cable -- even at Sony prices -- is only US$50; you can find it for US$20 if you shop around.

Also, transferring via 1394 is a digital copy, a data dump. No decompression or recompression occurs. Transferring DV around as baseband video, even digitally over SDI, subjects it to the small but definite degradation of repeated decompression/recompression.

If a digitally-perfect copy is a 10, and a point-the-camera-at-the-screen-and-pray transfer is a 1, here's how DV picture quality holds up over different transfer methods:
 

Topics on this page:

• The DV Formats Tabulated - A comparison of the various DV25 formats.
• Standards Documents - Where to find the defining documents for the various DV25 and DV50 formats.
• DV - Blue Book, IEC 61834, IEC 61833
• DVCAM - not a standardized format, but Sony has useful info on it.
• D7, D9, DVCPRO50 - SMPTE standards
• File Formats - AVI, OpenDML, QuickTime

  *Interformat interchange:

SP-mode DV plays back in all three format VTRs; DVCPRO VTRs require a cassette adapter to play back miniDV tapes.

DVCAM plays back in most Sony DV VTRs excepting the DCR-VX700 and DCR-VX1000 camcorders which were designed prior to the introduction of DVCAM. With the exception of some recent (2001+) Panasonic and possibly JVC machines, DVCAM does not play back on other manufacturer's DV equipment. Check with the manufacturer to find out if your machine will play back DVCAM.

Early model DVCPRO VTRs (made before June 1997) require an EPROM upgrade to allow the servos to track DVCAM. Check the serial number: it's of the form MYxxxxxxx, where M is a month letter, A-L, and Y is the last digit in the year. F7xxxxxxx means the machine was built in June 1997, and it's OK. H6xxxxxxx would mean the machine was born in August of 1996 and the EPROM upgrade would be required. All current DVCPRO equipment plays back DV and DVCAM.

To play back DV or DVCAM in a DVCPRO machine, use the setup menus to specify DV or DVCAM before you insert the tape! The playback mode "locks in" when the tape is inserted, so if you set DV or DVCAM mode after loading the tape, playback will still be attempted as if the tape were a DVCPRO tape.

PAL 4:2:0 DV and DVCAM played back on a DVCPRO are digitally resampled to generate a PAL 4:1:1 DVCPRO signal.

DV in LP mode will not play back in DVCAM or DVCPRO VTRs other than the DSR-2000.

80-minute miniDV tapes will not play back in DVCAM or DVCPRO VTRs.

miniDV tapes cannot be played back in the NewsByte VTR even with the cassette adaptor.

DV in SP mode (60-minute or shorter tapes) appears to be the universal tape format: it will play back in any of the VTRs.

DVCPRO VTRs and the DSR-1xxx/2000 appear to be the universal playback VTRs: they'll play back any of the DV-based formats. Only the DSR-2000 plays DV LP mode tapes, however.

The 4X high-speed transfer decks will not perform 4X play with a DV cassette!

Some DV camcorders will play back (but not record) tapes in the opposite standard, i.e. PAL playback in NTSC machines, and NTSC playback in PAL machines. The DSR-50 DVCAM VTR also offers this "foreign tape" playback capability.

The DSR-50 VTR and DSR-PD150 camcorder will record in either DV or DVCAM modes.

The DSR-11 records and plays back both DV and DVCAM; it also records and plays back both NTSC and PAL! Note however that it does not transcode between NTSC and PAL formats.

The Panasonic AJ-D455 is the only VTR that will play back any of the DV25 format over 1394, either as Blue-Book -compatible DV, or as D-7-compatible DVCPRO25 data!

The Sony DSR-1500A will play back DVCPRO25 over 1394 as DVCPRO data.

[Bernard Adolphe supplied many technical figures for Digital8, and reported that over an 8 month period he had no dropouts on Video8 tape, unlike the performance from his DV format TRV900. Merci, Bernard! Tom Hardwick supplied PAL Digital8 runtimes; thanks!]

**DVCPRO std. cassette run times:

The "standard" standard cassette holds 123 minutes of tape, but there is a newer, 184 minute tape load available using the same sized cassette. All DVCPRO equipment accepting the std. size cassette should be able to record or play for 184 minutes, but only the newer equipment (such as the AJ-D215, AJ-D850, later model AJ-D230s, and the 400-series VTRs) has been programmed to "understand" the larger load. If you put a 184 min. cassette into an older bit of equipment, it'll think that such a cassette can only hold 123 minutes, and as a result operations like fast-forward or rewind may only work as expected for 2/3 of the tape, after which the machine will slow the tape down, expecting it to end. The operation will proceed at this reduced speed while the machine is waiting for the tape to end (any minute now!); this can take quite a while... Before using the longer tape in older gear (600-series and 700-series VTRs, AJ-D200 and 210 cameras, and pre-NAB-1999 AJ-D230 VTRs), you might want to check with your Panasonic rep, or at least do a dry run to see how the older gear will behave with the longer tape.
 

Standards Documents

DV

The current DV standards document is IEC 61834. This publication of the International Electrotechnical Commission, a standards body related to the ISO and the ITU, is an evolving, ongoing work; as of September 1999 parts 1, 2, 4, and 5 are actively published and updated, with other parts in committee review (some parts due for publication, other parts apparently languishing, for example the parts dealing with recording of now-obsolete HDTV systems). This document grew out of the Blue Book, using it as the "first draft."

Cost of the four parts currently available is approximately US$450. The best way to find this information is to search for IEC document number 61834 using the catalog search pages in either English or French. You can order the documents on-line from the IEC's secure server. 

IEC 61833 covers transmission of DV data using 1394, and is also available from the IEC. 

The original DV format standards document was the "Blue Book", officially titled Specifications of Consumer-Use Digital VCRs using 6.3mm magnetic tape; HD Digital VCR Conference, December 1994. The Blue Book was available from Mr. Mineo Mino, who held the position of:

File Keeper of Dissolved HD Digital VCR Conference and Manager of Development Planning and Technology Liaison,
Video Equipment Division,
AVC Company,
Matsushita Electric Industrial Co., Ltd.
1-15, Matsuo-Cho, Kadoma-Shi, Osaka, 571-8504, JAPAN

However Mino-san retired in 2001 and I do not have contact information for the current File Keeper, if there is one. Fortunately the information in the Blue Book is available in the IEC documents listed above.

Cost was reported to be around ¥50,000.
 

DVCAM

DVCAM standards documents are not generally available as far as I know.  However, Sony Canada offer a DVCAM Format Overview brochure (PDF) with most of the necessary info, as well as an excellent overview of DV-format compression, macroblock structure, block shuffling, and tape recording (a tip o' the hat to David Auner for this link, and J.C. Bouvier for telling me when it moved). Sony's excellent Canadian DVCAM site also offers PDFs of equipment manuals, brochures, and other truly useful information. Why can't Sony USA do half as good a job?

DVCAM is very close to DV; if you take the information in IEC 61834 and compensate for (a) 50% higher track pitch, track width, and tape speed; (b) 1/3 shorter run times per tape length; (c) defaulting to locked audio; and (d) no support for LP mode, you should have most of what you need. Conversely, you can reverse-engineer a lot about DV from this DVCAM information – and unlike the DV standards documents, this info is free!
 

D-7 (DVCPRO), D-9 (Digital-S), DVCPRO50

The D-7 (DVCPRO) standards documents are
SMPTE 306M-1998, Television Digital Recording ---- 6.35-mm Type D-7 Component Format ---- Video Compression at 25 Mb/s ---- 525/60 and 625/50
and
SMPTE 307M-1998 Television Digital Recording ---- 6.35-mm Type D-7 Component Format ---- Tape Cassette.

The data structure for both DVCPRO and DVCPRO50 (and presumably, JVC's D-9 / Digital-S) is described in
SMPTE 314M-1999, Data Structure for DV-Based Audio, Data and Compressed Video ---- 25 and 50 Mb/s.

The D-9 (Digital-S) standards documents are
SMPTE 316M Television Digital Recording ---- 12.65-mm Type D-9 Component Format ---- Video Compression ---- 525/60 and 625/50
and
SMPTE 317M Television Digital Recording ---- 12.65-mm Type D-9 Component Format ---- Tape Cassette.

From SMPTE's website: "To order SMPTE documents, please fax, phone, email or postal mail your order with payment information to SMPTE Headquarters. You may make payments by credit card (American Express, MasterCard or Visa) or by a check payable in US dollars on a US bank."

SMPTE
595 West Hartsdale Avenue
White Plains, NY 10607 USA

Tel: +1-914-761-1100
Fax: +1-914-761-3115

email: smpte@smpte.org

Prices in US dollars as of September 1999:
 

306M-1998 (D-7 compression)	$55
307M-1998 (D-7 tape cassette)	$26
314M-1999 (DV25/DV50 data)	$34
316M (D-9 compression)	$50
317M (D-9 tape cassette)	$20

To be on the safe side, double-check these prices by reviewing current information on SMPTE's website.
 

File Formats

Basic AVI file format information is available from Microsoft (search online), as is a discussion of Type 1 and Type 2 DV AVIs.

The specification for DV Data in the AVI File Format , Version 1.01 is available from Microsoft as a self-extracting executable file (Mac users: download it and use Stuffit Expander to open it). It expands to an RTF text file.

The OpenDML extensions as used in DirectShow 5.1+ are available from Matrox as a PDF.

The root of all QuickTime documentation is here. If you want to get right into the file format, that's OK, too!