Talk:DV

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Contents 1 DV for data backup 2 Type-1 vs Type-2 3 1993 4 Color sampling 5 DVCPro timecode 6 terminology 7 MiniDV 8 What?! 9 Readers? 10 Video resolution 11 History and development of the DV format 12 Tape Lifetime 13 miniDV - DVC Pro compatibility 14 DV (miniDV) resolution again

[edit] DV for data backup

Is it appropriate to put a link to the software that is mentioned in the article? The article mentions software which allows a MiniDV camcorder to be used as a data storage device but doesn't give the name or a link; this seems foolish. If we're going to mention the existence of the software, we might as well give the name.

The only software I could find which meets the description is called 'DV Backup,' it's $45 shareware, and it's from http://www.coolatoola.com/.

Only one I know of is dvbackup, which is Free Software. I've never used it myself. --Brion 05:41, 20 Feb 2004 (UTC)

There's also another one for Windows, DV Streamer. Unfortunately, DV Backup is Mac OS X only, and dvbackup is Linux/Unix/POSIX OS only. Backing up data to DV reminds me of the old systems back in the 80's that allowed you to back up your computer's data to a analog VHS videocassette by installing a special ISA-bus card that interfaced to your VHS/Betamax/what-have-you VCR. Videotrax and Corvus were companies that made such hardware for backing up to VHS. misternuvistor 03:22, 2 February 2006 (UTC)

[edit] Type-1 vs Type-2

I've seen some mention of DV types 1 and 2. Could something about this possibly be mentioned in the article? Certain software apps only support type-2. — SimonEast 08:39, 15 Oct 2004 (UTC)

If anyone is able to add this information, I would like the article to tell how to diagnose whether a file is Type 1 or Type 2. Robert K S 14:48, 1 February 2007 (UTC)

[edit] 1993

I believe the last line of this article is flawed; "In 1993, Sony, JVC, Canon, and Sharp have come up with the HDV standard for high-definition camcorders." I don't believe it should say "In 1993, Sony, JVC, Canon, and Sharp have come up with the Hi8 standard for 8MM camcorders."

[edit] Color sampling

The Color Sampling section should probably be reworked into just advantages/disadvantages, since it's halfway there already.

[edit] DVCPro timecode

Doesnt the DVCPRO also have a separate track for timecode, this is missing in the article? In the article only the extra audio cue track is mentioned.

[edit] terminology

At the beginning of the article, DV is referred to as a "video format", then down below, as a "codec". Is this poor terminology, or is the codec a sub part of the larger format? As far as I can tell, there are codecs, and there are tape sizes/formats. The two are technologically distinct, but in implementation, each tape has a given format that it uses, and there are few (no?) cases where two cameras use the same type of tape but write a different codec. Datarate is a whole other bag of chips. Do DVC pro 50 and DVC pro HD really use the exact same codec, but with a doubled data rate? What hardware at each end of the process supports these things?

--Johnjosephbachir 01:22, 5 Dec 2004 (UTC)

Technically, there ARE definitely cameras that record vastly different formats to the same cassette. Take Digital8/Hi8/Video8 as an example.

The term "dv" in common language is probably used to mean both things (both the codec on the one hand, and the whole format including tape speed, the physical cassette etc on the other). The data stream that is recorded to tape in the Digital8 format is also dv in the correct sense of the word (that is, referring to the codec or data stream). Digital8 is dv. Thus, if referring to a minDV cassette, the correct term to use would be just that (minDV). But I don't think consumers are often aware of this distinction. Thus, I think the term "dv" can refer to a whole lot of things, for example minDV.

dsandlund 09:45, February 12 2006 (CET)

[edit] MiniDV

The link to minidv just goes back to itself, I'm removing it, someone please tell me if I'm doing something wrong. Szabo 23:53, 9 Dec 2004 (UTC)

[edit] What?!

At the end of the DVCPRO section, it says:

"Willians Terence Hills is the very important videoast the USA. In América Latin the brazilians e the mexicans are the more importants videomaker, the name of the José Patrício Neto in Brazil (Maranhão) and Roberto Mendez in Mexico are stars."

What the hell is this about? Some sort of database error?

[edit] Readers?

Does anyone know if there are any reader/writers that allow people to read/write to/from dv and/or minidv tapes on a computer without using a camera? --4.245.7.3 07:18, 20 May 2005 (UTC)

Yes, at school we use a device that my teacher referred to as a "DV Camdeck", which looks like a smaller VCR; connects to the computer via firewire and accepts MiniDV, DV, and rear composite inputs. I'll try to get a more specific model number. Ahanix1989 14:33, 15 September 2006 (UTC)

[edit] Video resolution

what's the video resolution of ordinary mini dv recordings? how does it compare to DVD? RustyCale 13:27, 22 May 2005 (UTC)

I'm not a video expert, but I would assume that all else equal, mini dv tape would be higher resolution than dvd. Of course a lot depends on what kind of camera is used, and many of the cheaper mini-dv camcorders don't have the best micro-processors, zoom lenses, image processing chips, etc. But with the same camera, it would make sense that the mini dv tape would be higher resolution because one hour in the standard sp mode is about 13 GB, whereas two hours of standard bit-rate dvd is about 4.5 GB. So the DVD has a lot fewer GBs per hour, indicating that it's probably a somewhat lossy compression. That should change with the next generation of dvds - blue ray and/or HD-DVD. Of course with a traditional CRT tv you can't see any of that difference (except maybe with the dvd player's zoom function), since the tv itself is too low resolution. Blackcats 07:49, 30 May 2005 (UTC)

I would like to clarify two things here: First, dv is a lossy format, just like dvd/mpeg2. Compression artifacts are very visible at magnification. Second, the two formats (dv and mpeg2) store video in completely different ways, making comparisons by bitrate rather irrelevant I'm afraid. The answer is that It depends.

One point that really should be brought into the article however is the actual pixel resolution of the dv format. This rather central piece of information has been completely overlooked.

dsandlund 09:39, February 12 2006 (CET)

But keep in mind that the contrast is not compressed, only the color space. So DV is only a lossy format for the color informaiton in the compressed video.

LexieM 19:17, 27 February 2006 (UTC)

No. Both are compressed, using the same method (which is almost identical with JPEG-compression). What you probably have meant, was, that before aplying that compression (DCT, quantizing etc.) the colour informations are subsampled (making the arrays of Cb- as well as Cr-numbers, which represent the picture, smaller), while the luminance/grey array is preserved (at 720x480 or 720x576 values). So, luma and chroma don't differ in compression, but in subsampling. Btw, 720x480x30 (and 720x576x25 too) makes 10.368.000 values(usually bytes) per second, which is ~3x the datarate of DV.

ShapedNoise 22:26, 25 February 2007 (UTC)

When talking about recording a full frame (not widescreen) video with an aspect ratio of 4:3, Mini DV typically records with a resolution of 720x480 rectangle pixels. DVD uses square pixels, which squeezes the resolution to 640x480, creating a true 4x3 aspect ratio. 720x480 has an aspect ratio of 3:2 because of the rectangle pixels.

El Mariachi94 05:50, 1 December 2006 (UTC)El Mariachi94

I think you've confused a few different things? Both DV and DVD use rectangular/non-square pixels. In NTSC DV, not all the pixels are used for active picture area, so this is why the 720X480 pixels don't make a 4:3 picture (although the active picture area does). [1] Something like that. Glennchan 03:28, 2 December 2006 (UTC)

Reading the link you've posted thoroughly, made my head ache :(

But, i'd like to say this: the number 720 is common for both NTSC and PAL. I've read, that the CCIR601 standard defines the sampling frequency (for digitizing of those analog formats) to be 13.50 MHz, and to be equal for them both. The length of PAL row is 64.0 us and the active/visual part lasts 52.0 us, NTSC's row lasts 63.5 us and its active part ...('ve forgot,sorry). These intervals are almost equal on both sides of The Ocean.

So, to simplify the everyday bread of tv-companies (NTSC <-> PAL transcoding), they've decided to apply the same f_samp for both. Thus the horizontal resampling would be no longer needed; though the difference in number of rows (height of picture, measured in pixels) as well as in framerate, still stays alive.

Another limit, which applied to their deciding: Both width and height of the digitized pic must be a multiple of 16, because the compression involves slicing into 8x8 tiles, and because the Cb and Cr parts are twice-subsampled (2x8=16) (an eventual use of 4:1:1-subsamp probably implies even 32 instead of only 16).

So, checking the numbers against 16: 720-ok, 360(=720/2)-fails; 704-ok, 352(=704/2)-ok; 576-ok, 480-ok.

Another computations: 720px / 13.50Mhz = 53.33 us, which is a bit more than that 52.0 us. So, creating 601'compatible material by digitizing analog PAL (NTSC probably too) (e.g. a playing VHS or a demodulated live TV signal) will introduce some black pixels/columns on the left and right side. On the other hand, if it's created by native digitally-acquiring devices (like DV, DigiBeta,..), then even the sidemost pixels contain valid visual info and there's no need/reason to crop them. Please look at the grab-monitoring or replay window to check if i'm not fooling.

DV and DVD (and probably most other Stand.Def. formats too) use the same 'grid' of pixels. In US&JP, it implies a pixel to be slightly-portraitic, and in Eur slightly-landscapic (cause they both have the same number of 'columns', but differ in number of rows). Thus, doing some resampling when converting from DV to DVD (not to confuse this with transcoding), is, imho, not a good idea.

Some people don't like nonsquared pixels stretched or shrinked on their monitors. Hmm. I also didn't. But. Doing the resampling, with a factor very near one (e.g. 0.92, 1.07, or so) is a very risky operation, especialy if the content is very sharp (i.e. the content goes almost to the Shannon's limit). Then, such resampling may end with very ugly results. Maybe that using some more clever algorithm (e.g. bicubic instead of linear) heels this a bit, but still is far from ideal. Paradoxially, resamp. with more-far-from-1 coeff. (like 0.73 or 1.39) will probably usually end with much nicer results.

So, i'd rather stand the non-ideal proportions than having to stare at the resampling artifacts. Additionally, many monitors (CRTs, and LCDs too) don't have the same ratio of native resolution and physical screen dimensions (e.g. view 1280x1024 (=5:4) on 16"x12" (=4:3) screen. So sometimes/often the nonsquareness may survive even after resampling :(

Finally, i've got a very constructive suggestion: we should throw some putrefying tomatoes at those standard-creators and device manufaturers, as an expression of our big thanks for that pixel ratio chaos they've created for us :)

Enough for today, tired, going to cool-down my brain :) See you laters. Give some response in between. ShapedNoise 01:45, 26 February 2007 (UTC)

[edit] History and development of the DV format

I would like to see something added about the history and development of the DV format. It also should be mentioned (if I am correct in this) that the Digital-8mm format uses the DV codec. —The preceding unsigned comment was added by LexieM (talk • contribs).

It would be nice to see information about what company/companies/consortium originally created the format, since the article seems to say that ISO standardization came after original "Blue Book" development. —SudoMonas 05:02, 14 August 2006 (UTC)

I was involved in the standardisation. It started in 1990 as a cooperation between Philips, Thomson, Matsushita and JVC. Later on Sony joined. When the standard was more or less agreed between these 5 companiers all other were invited to join the DV consortium. There were many discussion on how to add new features that were not present in existing systems. In the end some features that were realised were: adding meta data (subcode),high speed forward/reverse whilst being able to read the metadata, memory-in-cassette to read metadata without inserting the cassette in a player, post-edit of audio tracks, etc.

[edit] Tape Lifetime

Does anyone know if/when the tapes fatigue? GChriss 22:35, 18 March 2006 (UTC)

To add to this question, a section on proper head cleaning would be helpful as well. Thanks, GChriss <always listening><c> 19:15, 21 September 2006 (UTC)

I guess the real question is, can the tapes be used over again without a noticable degredation in quality. If so, how many times? 205.157.110.11 01:50, 2 November 2006 (UTC)

At a certain point, there would be too much tape shedding of the tape surface. This was a problem with LINEAR editing I believe, from shuttling the tape around. ME is not quite as robust as MP tape. I don't have actual figures myself though. Glennchan 22:28, 2 November 2006 (UTC)

This is also one of the more practical differences between small format MiniDV tape and Medium format DVCAM tapes. DVCAM tapes seem to be built much more robustly and tend to lastlonger

[edit] miniDV - DVC Pro compatibility

This item intruiges me: "MiniDV tapes can be played with a cassette-adaptor.". Now I must have missed something. I believed the DVC Pro tapes are based on Betacam shells (and therefore on domestic Betamax) which is a 1/2" tape format. So what kind of adaptor could allow a miniDV tape to work in a 1/2" mechanism? This can't be. So either I'm wrong about the shell size of DVC Pro, or this adaptor is a non-starter. Explanation welcome! Colin99 17:45, 4 July 2006 (UTC)

You are indeed wrong about the shell size. DVCPRO cassettes use the same shell design as DVCam, but DVCPRO aren't available in the 'mini' size, hence the need for an adaptor if you want to play 'mini' cassetees in a DVCPRO VTR. One cassette adaptor model is the Panasonic AJ-CS455: http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=227684&is=REG

[edit] DV (miniDV) resolution again

Unlike DVD,VCD, etc., there is no resolution data included in the DV (miniDV) page. I am really an amateur. I noticed and read your technical discussion on DV resolution, but I am still in the mist - Is there simply a DV resolution of ???x??? can be quoted? or how can we compare the resolution between DVD and DV ?--Chan w 06:16, 9 March 2007 (UTC)

720x480. -seinman 07:43, 9 March 2007 (UTC)

720x480 is for 525 line - 30 frame per second systems (as used in NTSC)and 720x576 for 625 line - 25 frame systems (as used in PAL, SECAM)