What's the difference between DVD and Blu-Ray ?

Other Questions :



Where can I buy a VCR / DVD / Blu-Ray combo ?

Will blank Blu -Ray discs come available soon ? )So we can record movies and stuff off of tv).



VHS tapes are still useful for me.

# 1 They're cheap and easy to use for recording

# 2 Tapes run 6 - 8 hrs. on EP mode (you could fit 3 - 4 movies on one tape. something you can't do with dvd yet.)



DVDs for me are complicated when it comes to recording stuff. I still use VHS tapes for recording stuff.



My fear : I'll have to replace all my millions of tapes.

What's the difference between DVD and Blu-Ray ?
Well, there are many, many differences.



Blu-Ray discs use a Blue-Violet (405nm) laser to read tiny pits in the disc; DVDs use the same basic idea, but with a red laser (650nm). The shorter wavelength allows smaller pits, and allows tracks to be packed closer together, so a Blu-Ray disc stored 25GB per layer, while a DVD stores 4.7GB per layer.



The data is at 0.1mm thickness on a Blu-Ray disc, at 0.6mm thickness on a DVD. Both support single and dual layer discs, though in theory Blu-Ray has room for additional layers.



Both discs are always "data" discs when formatted, both use a file system called UDF, though the Blu-Ray format is a updated version of UDF, and most PCs don't yet have this built-in. A DVD with the appropriate files in the right locations is called a DVD-Video disc, and will play on any standard DVD player. Blu-Ray supports two kinds of video discs, BDAV or BDMV. BDAV is just a single video that plays without interactivity... BDMV can be full of menus, popups, etc.



DVDs use a fairly simple means of navigation between menus, buttons, etc. BDMV Blu-Ray discs are authored in BD-J, a dialect of the Java virtual language/virtual machine. Thus, a BD can, in theory, run applications like a PC might, but of course, they would currently be pretty slow and without printers, hard drives, etc. But this certainly allows for far more complex interactivity than on DVD (a single DVD title set, for example, is limited to 99 menus).



DVD's support MPEG-1 and MPEG-2 video up to 720x480 NTSC, 720x576 PAL. They support Dolby Digital (AC-3) and PCM (WAV), and usually MPEG Layer 2 audio, DTS is also an option (and originally Sony's SDDS, but it never caught on). Blu-Ray supports MPEG-2, VC-1 (essentially Windows Media 9) and AVC (originally called H.264, it's at least twice as compact as MPEG-2 for the same quality) for video, and many different audio formats, including multichannel PCM (uncompressed). Video is HD, up to 1920x1080.



And yes, you can buy recordable Blu-Ray discs.. the last stack of BD-Rs I bought ran me around $9.00 a disc... that's not cheap, compared to $0.20 DVD-Rs, but it's also not the $50 a disc they were on introduction.



VHS quality is so low, I don't use it. Never did much. I do have two SVHS decks, but they're largely just taking up closet space. When you put 3-4 movies on a VHS tape, you're taking what's bad quality and making it abysmal. You CAN do the same thing on DVD.. you can encode in MPEG-2 at 352x480 or MPEG-1 at 352x240 (both NTSC) and easily fit eight hours of video on a DVD-9 (two layer).. but again, DVD-5's run about $0.20 each in bulk. There's no any significant point in trying to cram 3-4 films onto a single DVD.



Moving to DVD doesn't suddenly make your VHS deck fail, or your tapes stop working... I had DVD and VHS coexisting for awhile. I never bought pre-recorded VHS, due to the horrible quality, so it was really used only for time-shifting... that's been well addressed, first by a first-gen TiVo, then an HD-PVR.



Yeah, authoring DVDs on a PC can be a little more work than recording VHS, but you gain power in the process, control over what you're doing. A DVD recording deck, which is relatively cheap today, would probably not be much more difficult to use than a VHS deck. I wouldn't hold my breath for a VCR/DVD/BD combo anytime soon... VHS is pretty much being phased out by the CE companies. What's the difference between DVD and Blu-Ray ?
Blu-Ray uses a blue laser instead of a red one. DVDs and Blu-ray use basically patterns of small holes to hold data. Since blue light has a shorter wavelength than red you can use smaller holes and put them closer together so the blu-ray disks can hold more data.