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Kamis, 10 Juli 2008

DVD Recorders: Getting Started

IMO, these sd work 'like a VCR' as far as recording and playback. There are models w/ harddrives, VHS players, etc. built in, but to me that's overboard.

Bells and Whistles

The VHS option is not bad, but you most likely already have one you can plug into the inputs of the DVD recorder.

I have a DVD recorder for archiving TiVo shows as opposed to accessing my TiVo from my PC. This is nice because it means I can also archive VHS tapes, camcorder tapes, etc. w/no extra work.

I do have a TV card in my PC so I can do this, but using the DVD recorder is easier.

My motto is: buy what you WILL use and not what you CAN use.

I've bought lots of things that CAN do a lot, but in reality I don't use all the extra features. Not in all cases, but in this case, I say pass on the bells and whistles.

Again, there are models w/ all types of features, but if you buy one that is a DVR, DVD recorder, VCR, TV tuner all in one and one part breaks, it's all broke.

Realize Something About Technology

Remember - this is new technology and will only get better and cheaper. If you buy the top of the line today, it's going to be out of date and/or cheap tomorrow. Test the waters w/ a 'good' model and upgrade when the time is right.

Editing Your Recordings

Chances are - you won't. It's a pain for the most part and usually requires DVD-RAM or DVD-RW discs to do it and they're more expensive. If you have a lot of free time for this, you're a rare person.

I was looking for this type of solution in getting ready for having a baby and I knew I wasn't going to be sifting through and editing hours of video.

If you're really interested in editing, look in to PC options. Pinnacle, ArcSoft, Adobe, etc. - they have good solutions for that.


DVD+R and DVD-R are like VHS and Beta: they're both ok right now, but eventually we'll probably land on one or the other. It seems to be leaning towards DVD-R which tend to be less expensive also.

Many recorders and players do both, but cost more. I say save some money, pick one (probably DVD-R) and move on. If you pick the wrong one, chances are in a couple years you'll be buying a new one anyway. Moreover, you'll probably be able to get a cheap one w/ a built in converter or two trays to duplicate one to the other.

DVD-RAM and DVD-RW are the rewritable types. They're more expensive and for my purposes aren't worth worrying about.

My Recommendation

I got the Panasonic DMR-E55K:

It records to DVD-R like a VCR. I don't use it to record live TV so I don't use VCR+, but it has it. Also, it has TimeSlip which lets you watch something while it's recording (start recording "24" at 8pm and start watching it from the begining at 8:20 to speed thru commercials like a TiVo). Again, I don't use this, but it has it.

Plain and simple, it records my TiVo, camcorder, digital camera (RCA cable output), VCR, etc. to DVD - that's what I want it to do and that's what it does. It's easy, creates a good menu w/ thumbnails and my chosen titles, it's a name brand w/ good reviews and was fairly cheap (there was a rebate at the time).

Also, it plays CDs and mp3 CDs w/ a good interface so not only does it replace a CD player, but since you can put so many songs on one CD, it replaces a CD changer.

An interesting trick: If you have a digital camera w/ RCA cable output, you can hook it directly into the dvd recorder and create a quick slide-show dvd. Many cameras even have a slide show function built in! You can use the sound from a music channel, CD, etc.


If you're going gung-ho into all the nitty gritty about DVD recorders, you're either just starting here or haven't bothered to read this far. If you're looking for a good, relatively cheap solution to digitize your tapes, archive TiVo, etc., I recommend the Panasonic DMR-E55K.

By Bear Cahill

Recordable DVD Formats Explained

Picking your way through the ton of information available on recordable DVD formats can be a nightmare. To help you out, we've done our best to distill it into this summary.

There are five recordable versions of DVD; DVD-R for General, DVD-R for Authoring, DVD-RAM, DVD-RW, and DVD+RW. None of the formats is fully compatible with the other although there are drives which will read, and in some cases write to more than one format.

DVD-R for General and DVD-R for Authoring are essentially DVD versions of CD-R. And DVD-RW is a DVD version of CD-RW. All three formats can be read in standard DVD-ROM drives and in most DVD video players. The difference between DVD-R for General and DVD-R for Authoring is that DVD-R for General is a format intended for widespread consumer use and doeasn't support 'professional' features such as piracy protection or duplication in mass duplicators. The Pioneer DVD-RW drive which is the most popular PC device for writing to DVD uses the DVD for General format. And as as the case with CD, DVD-RW is essentially the same as DVD-R except that it can be erased and written to again and again.

DVD-RAM is slightly different as it is a sector based disc which mounts on the desktop of a PC when inserted into a drive. Files can then be copied to it in the same way as any other mounted media. Some single-sided DVD-RAM discs can be removed from their caddy and inserted in a DVD-ROM drive which will then be able to read the content of the disc.

There are DVD video recorders which use the DVD-RAM format. This enables themn to pull off clever tricks like timeshifting - where you can watch the beginning of a programme you have recorded while you are still recording the end on the same disc.

DVD+RW is the newest format and not supported by the DVD Forum, the body which sets the standards for DVD. However, it is supported by some of the biggest electronics and computer manufacturers, and is therefore likely to stick around.

It is also the format used by Philips in its DVD video recorders. Despite not being authorised by the DVD Forum, DVD+RW is claimed by its supporterd to be compatible with more DVD video players than DVD-R and DVD+RW writers are found in PCs from quite a few manufacturers.

In early 2006, things are set to get even more complicated with the introduction of two new formats, HD-DVD and Blu-ray, but that's a whole other story...

By Kenny Hemphill

Video Encryption

What is Video Encryption?

Video Encryption is an extremely useful method for the stopping unwanted interception and viewing of any transmitted video or other information, for example from a law enforcement video surveillance being relayed back to a central viewing centre.

The scrambling is the easy part. It is the un-encryption that's hard, but there are several techniques that are available. However, the human eye is very good at, spotting distortions in pictures due to poor video decoding or poor choice of video scrambling hardware. Therefore, it is very important to choose the right hardware or else your video transmissions may be un-secure or your decoded video may not be watchable.

Some of the more popular techniques are detailed below:

Line Inversion:

Method: Whole or parts of the signal scan lines are inverted. Advantages: Simple, cheap video encryption. Disadvantages: Poor video decrypting quality, low obscurity, low security.

Sync Suppression:

Method: Hide/remove the horizontal/vertical line syncs.

Advantages: Provides a low cost solution to Encryption and provides good quality video decoding.

Disadvantages: This method is incompatible with some distribution equipment. Obscurity (i.e. how easy it is to visually decipher the image) is dependant on video content.

Line Shuffle:

Method: Each signal line is re-ordered on the screen.

Advantages: Provides a compatible video signal, a reasonable amount of obscurity, good decode quality.

Disadvantages: Requires a lot of digital storage space. There are potential issues with video stability. Less secure than the cut and rotate encryption method (see below)

Cut & Rotate:

Scrambling Method: Each scan line is cut into pieces and re-assembled in a different order.

Advantages: Provides a compatible video signal, gives an excellent amount of obscurity, as well as good decode quality and stability.

Disadvantages: Can have complex timing control and requires specialized scrambling equipment

The cut and rotate video encryption method is probably the best way of achieving reliable and good quality video encryption, an example of a good implementation of this system is in the Viewlock II

Implementing vice scrambling

The video scrambling hardware, in particular the decoder should function correctly even if there is a noisy (for example having what are commonly known as 'snow' on the screen. 'Snow' is when there are flecks on your TV screen, often seen in poor reception areas) or unstable signal. If the link to the encrypted signal should stop working then this should not be a problem. The link between the video encoder and video decoder should be regained and the decryption quickly continued.

The very nature of security camera systems is that they are often outdoors as so must be able to withstand the rigours of the weather. The video encryption hardware should be stable under or protected from the effects of rain, sunlight, extreme heat and cold. It should not be damaged if there is a power spike in the supply. In these systems the video encoder emits a wireless signal to the video decoder unit before it is viewed, it obviously must be the case that the very act of broadcasting the signal does not effect the video encoding hardware and likewise the video encoding hardware should not effect the radio transmitter.

The most important item is that the video scrambling system should be secure, else why bother? It is amazing how some encryption methods can easily be cracked. For example certain cable television stations 'encrypt' their channel broadcasts via a relatively un complex method, which can easily be decoded using a number of cheap bits of electronics from radio shack. That would obviously be illegal! The cable TV's method of encryption is very crude, they usually just dynamically alter the vertical sync signal so that your TV cannot get a proper lock on it and so it scrolls randomly.

The other extreme is to scramble the transmitted video signal too much so that it is costly both in equipment and time to the video at the receiver. Remember that this is a 'live' video scrambling broadcast followed by a 'live' video decryption display. ANY electronics can be copied, given enough money and time, but making this process as hard as possible is of benefit as it at least delays the time when illegal copies will be available.

Finally and most obviously each user must have a unique encryption key so that other users of the system cannot view the transmitted video by accident or purpose without the key owners knowledge. The total number of possible user keys must be such that it is highly unlikely for someone to guess the correct key.

Basics of RAID

A couple of the recent Tech Tips from have made mention of RAID, but the level of detail required in those tips didn't shed much light on what RAID actually is. The number of e-mail responses and comments in the Readers Digress section was convincing enough that an introduction to the basics of RAID would be an appropriate Tech Tip, so here it is.


The word RAID sounds like it might describe something Marines conduct in Fallujah, or a can of what all roaches fear, but it is simply an acronym that stands for Redundant Array of Independent (or Inexpensive) Disks. Depending on who you talk to, the letter "I" can stand for either independent or inexpensive, but in my opinion independent is more appropriate, and far less subjective.

RAID generally allows data to be written to multiple hard disk drives so that a failure of any one drive in the array does not result in the loss of any data, as well as increasing the system's fault tolerance. I say RAID generally does this, as there are several RAID configurations that provide different approaches to redundancy, but some RAID configurations are not redundant at all. Fault tolerance refers to a system's ability to continue operating when presented with a hardware (or software) failure, as should be experienced when a hard drive fails in one of the redundant configurations of RAID.

The Hardware

The basic hardware required to run RAID includes a set of matched hard drives and a RAID controller.

RAID can be run on any type of hard drive, including SCSI, SATA, and ATA. The number of hard drives required is dependent on the particular RAID configuration chosen, as described later. I mention the need for matched hard drives, and although this is not absolutely necessary, it is recommended. Most arrays will only be able to use the capacity of the smallest drive, so if a 250GB Hitachi drive is added to a RAID configuration with an 80GB Hitachi drive, that extra 170GB would probably go to waste (the only time that this doesn't apply is in a RAID configuration called JBOD (Just a Bunch Of Disks); which really "isn't a RAID configuration" but just a convenient thing that a RAID controller can do - see "Basic RAID Configurations" below for more information). In addition to matching capacities, it is highly recommended that drives match in terms of speed and transfer rate as the performance of the array would be restricted by the weakest drive used. One more area that should be considered while matching is the type of hard drive. RAID controllers are generally for either SCSI, SATA, or ATA exclusively, although some systems allow RAID arrays to be operated across controllers of different formats.

The RAID controller is where the data cables from the hard drives are connected, and conducts all of the processing of the data, like the typical drive connections found on a motherboard. RAID controllers are available as add on cards, such as this Silicon Image PCI ATA RAID controller, or integrated into motherboards, such as the SATA RAID controller found on the Asus K8V SE Deluxe ( Motherboards that include RAID controllers can be operated without the use of RAID, but the integration is a nice feature to have if RAID is a consideration. Even for systems without onboard RAID, the relatively low cost of add on cards makes this part of the upgrade relatively pain free.

Another piece of hardware that is not required, but may prove useful in a RAID array is a hot swappable drive bay. It allows a failed hard drive to be removed from a live system by simply unlocking the bay and sliding the drive cage out of the case. A new drive can then be slid in, locked into place, and the system won't skip a beat. This is typically seen on SCSI RAID arrays, but some IDE RAIDS cards will also allow this (such as this product manufactured by Promise Technology:

The Software

RAID can be run on any modern operating system provided that the appropriate drivers are available from the RAID controller's manufacturer. A computer with the operating system and all of the software already installed on one drive can be easily be cloned to another single drive by using software like Norton Ghost. But it is not as easy when going to RAID, as a user who wants to have their existing system with a single bootable hard drive upgraded to RAID must start from the beginning. This implies that the operating system and all software needs to be re-installed from scratch, and all key data must be backed up to be restored on the new RAID array.

If a RAID array is desired in a system for use as storage, but not as the location for the operating system, things get much easier. The existing hard drive can remain intact, and the necessary configuration can be made to add the RAID array without starting from scratch.

Basic RAID Configurations

There are about a dozen different types of RAID that I know of, and I will describe five of the more typical configurations, and usually offered on RAID controller cards.

RAID 0 is one of the configurations that does not provide redundancy, making it arguably not a true RAID array. Using at least two disks, RAID 0 writes data to the two drives in an alternating fashion, referred to as striping. If you had 8 chunks of data, for example, chunk 1, 3, 5, and 7 would be written to the first drive, and chunk 2, 4, 6, and 8 would be written to the second drive, but all in sequential order. This process of splitting the data across drives allows for a theoretical performance boost of up to double the speed of a single hard drive, but real world results will generally not be nearly that good. Since all data is not written to each disk, the failure of any one drive in the array generally results in a complete loss of data. RAID 0 is good for people who need to access large files quickly, or just demand high performance across the board (i.e. gaming systems). The capacity of a RAID 0 array is equal to the sum of the individual drives. So, if two 160GB Seagate drives were in a RAID 0 array, the total capacity would be 320GB.

RAID 1 is one of the most basic arrays that provides redundancy. Using at least two hard drives, all data is written to both drives in a method referred to as mirroring. Each drive's contents are identical to each other, so if one drive fails, the system could continue operating on the remaining good drive, making it an ideal choice for those who value their data. There is no performance increase as in RAID 0, and in fact there may be a slight decrease compared to a single drive system as the data is processed and written to both drives. The capacity of a RAID 1 array is equal to half the capacity of the sum of individual drives. Using those same two 160GB Seagate drives from above in RAID 1 would result in a total capacity of 160GB.

RAID 0+1, as the name may imply, is a combination of RAID 0 and RAID 1. You have the best of both worlds, the performance boost of RAID 0 and the redundancy of RAID 1. A minimum of four drives is required to implement RAID 0+1, where all data is written in both a mirrored and striped fashion to the four drives. Using the 8 chunks of data from the example above, the write pattern would be something like this? Chunks 1, 3, 5, and 7 would be written to drives one and three, and chunks 2, 4, 6, and 8 would be written to drives two and four, again in a sequential manner. If one drive should fail, the system and data are still intact. The capacity of a RAID 0+1 array is equal to half the total capacity of the individual drives. So, using four of the 160 GB Seagate drives results in a total capacity of 320GB when configured in RAID 0+1.

RAID 5 may be the most powerful RAID configuration for the typical user, with three (or five) disks required. Data is striped across all drives in the array, and in addition, parity information is striped as well. This parity information is basically a check on the data being written, so even though all data is not being written to all the drives in the array, the parity information can be used to reconstruct a lost drive in case of failure. Perhaps a bit difficult to describe, so let's go back to the example of the 8 chunks of data now being written to 3 drives in a RAID 5 array. Chunks one and two would be written to drive one and two respectively, with a corresponding parity chunk being written to drive three. Chunks three and four would then be written to drives one and three respectively, with the corresponding parity chunk being written to drive two. Chunks five and six would be written to drives two and three, with the corresponding parity chunk being written to drive one. Chunks seven and eight take us back to the beginning with the data being written to drives one and two, and the parity chunk being written to drive three. It might not sound like it, but due to the parity information being written to the drive not containing that specific bits of information, there is full redundancy. The capacity of a RAID 5 array is equal to the sum of the capacities of all the drives used, minus one drive. So, using three of the 160GB Seagate drives, the total capacity is 320GB when configured in RAID 5.

JBOD is another non-redundant configuration, which does not really offer a true RAID array. JBOD stands for Just a Bunch Of Disks (or Drives), and that is basically all that it is. RAID controllers that support JBOD allow users to ignore the RAID functions available and simply attach drives as they would to a standard drive controller. No redundancy, no performance boost, just additional connections for adding more drives to a system. A smart thing that JBOD does is that it can treat the odd sized drives as if they are a single volume (thus a 10GB drive and a 30GB would be seen as a single 40GB drive), so it is good to use if you have a bunch of odd sized drives sitting around - but otherwise it is better to go with a RAID 0, 1 or 0+1 configuration to get the performance boost, redundancy or both.

Final Words

Implementing RAID may sound daunting to those unfamiliar with the concept, but with some of the more basic configurations it is not much more involved than setting up a computer to use a standard drive controller. But, the benefits of RAID over a single drive system far outweigh the extra consideration required during installation. Losing data once due to hard drive failure may be all that is required to convince anyone that RAID is right for them, but why wait until that happens.

TiVo: An Introduction for the Few Who Dont Know Yet

TiVo will change your life... for the better. Plain and simple: record shows by telling TiVo to record them (not when, what channel, how long, etc.), record all new episodes of X, record all movies w/ so-and-so in them, etc.

High Points:

Most people know the basics of the concept. Here's the low-down on the things I'm asked most...

1. You can record one thing and watch something else already recorded.

2. You can get a dual tuner TiVo, but you'll need two SEPARATE feeds to the TiVo (i.e., two lines from your satellite dish). Then you can record 2 things at once or watch one/record another. These are more expensive, but you can get a DirecTiVo w/ dual tuner cheaper and then the monthly TiVo fee is about half normal.

3. Pause live TV - if you don't realize the value of this, I can't explain it. :)

TiVo has many different versions which all some slight variations. If you want to go beyond 'average guy' level, check out this forum.

Comparison to ReplayTV:

TiVo seems to have a better interface from what I've seen and what others have said. It's easier to use. However, ReplayTV is more easily hackable - you can access it from the web and the PC easier to convert/archive shows, etc. I have a DVD recorder for this which is another post for another time.

Both can be made to do mostly the same things, but you get the idea.

My Suggestion

I recommend the DirecTiVo Hughes HDVR2 (dual tuner) w/ the Triple LNB dish (this is the oval dish w/ 4 lines from it and it's HDTV ready). It's got the satellite converter box built in so it's only one box to deal w/, the TiVo monthly fee is less and it's dual tuner.

This model isn't as hackable as some TiVo's, but it can do some and if you want to go beyond the basics than you probably haven't read this far.


By Bear Cahill

Expert Guide to DVD Camcorders

Thinking about a mini DVD camcorder? You're not alone, it's a rapidly growing sector of the camcorder market, with Hitachi, Sony and Panasonic all making more than one mini dvd camcorder.

These camcorders differ from regular digital video cameras in one important way - they record video onto mini DVD discs, rather than DV tape. This has a number of advantages. DVD discs are more robust than tape and won't get chewed up in the camera. Although this is thankfully a rare occurance, it scares me every time I here a strange noise coming from my camcorder, so it's with bearing in mind.

The second advantage is that DVD discs are random access, compared to tape on which everything is recorded sequentially. This means that there's no need to rewind and fast forward to find the clip you're after, just select it from the menu. Some cameras even allow you to perform basic editing functions on-camera. An additional side-benefit is that a mini DVD camcorder doesn't have tape heads to get worn or dirty as happens in regular mini DVD cameras.

And thirdly, you can easily watch your home movies by removing the DVD from the camera and playing it in practically any DVD player.

However, there are negative factors to. The most siginificant one is that video is encoded as MPEG-2 on a mini DVD camcorder, as opposed to DV format. This means that it needs specialist software to edit - you can't just use your regular video editing program (unless it specifically supports MPEG-2). And if a Mac user you're out of luck, as there are no MPEG-2 editing applications for the Mac.

Also, mini DVD camcorders tend to cost more than similarly specified mini DV cameras. And the media is also more expensive. However, if you don't intend editing your movies and don't mind the extra cost, a mini dvd camcorder does offer extraordinary convenience.

By Kenny Hemphill

Laptop Computers Instigate Classroom Revolution!

Have you noticed that laptop computers are beginning to dictate what happens in the classroom? Additionally, mobile technology is changing where learning takes place. This is especially true as laptops are entering the educational arena in ever increasing numbers.

Yet not all educators are quick to jump on the notebook bandwagon. They are waiting to see if laptop use is truly changing learning for the better. That's why schools such as Framingham State College in Boston and the Myron B. Thompson Academy in Honolulu are being scrutinized. Both schools have elected to use laptop computers as a major resource in their curriculum.

It must be noted that simply having laptop computer access does not change the learning process - the entire curriculum must change and merge technology with academics. Using a laptop is more than replacing paper and pencil with electronics. The entire relationship between the teacher and students must change. Teachers are no longer merely dispensers of knowledge but become facilitators in a learning process that takes place with additional tools for communication with students. This encourages greater student involvement, long recognized as a key to learning.

Professors actively engaged in education via technology see laptops as a way to give real life experiences to otherwise insipid theories. For instance, physics students can witness the breakdown of radioactive materials, math students can apply their knowledge of logic to projects that use spreadsheets, and english majors can evaluate peers' poetry and prose. With laptop availability in the classroom, access to additional information and knowledge is readily available.

So what do students think of the laptop trend? Well most find it invigorating. Rather than dealing with one dimensional lectures, teachers can engage the internet to show relevancy to daily life. Out of date, static texts can be set aside for breaking news stories - and so much more.

As schools show the link between laptops and learning effectiveness, the trend for laptop use will certainly grow. For those opposed to the technological revolution taking place in today's classrooms, perhaps the words of Maria Montessori should be heeded.

".....If education is always to be conceived along the same antiquated lines of a mere transmission of knowledge, there is little to be hoped from it in the bettering of man's future....."