CD & DVD
General frequently asked questions about CD & DVD
- Can CD-R writers create DVDs?
- Can I just copy files onto a CD-R like I would to a floppy?
- Can I use CD-R to copy my CDs?
- DVD Sizes?
- How come my 4.7 GB DVD isn't really 4.7 GB?
- How long does it take to burn a CD-R?
- Video File Comparison?
- What does "buffer underrun" mean?
- What is CD-R?
- What is DVD+R and DVD+RW?
- What is DVD+R DL (dual layer)?
- What is DVD-R and DVD-RW?
- What is DVD-RAM?
- What is ISO-9660 Standard?
- What is Joliet?
1. Q :Can CD-R writers create DVDs?
A : No. DVD uses a smaller wavelength of laser to make smaller pits in tracks that are closer together. The DVD laser must also focus more tightly and at a different level. (Return to Top)
2. Q : Can I just copy files onto a CD-R like I would to a floppy?
A : Not really. The process is usually a bit more involved than that, and requires special software that (usually) comes bundled with the drive. Some software does allow you to drag-and-drop, but it generally isn't used.
You don't need to write everything all at once, but when you're doing the writing you can't interrupt the drive, and you can't reclaim the space you've used. (Return to Top)
3. Q : Can I use CD-R to copy my CDs?
4. Q : DVD Sizes ?
A : The DVD sizes can be a bit confusing. There are basicly 4 different DVD Sizes,
DVD-5, holds around 4 700 000 000 bytes (4.7 GB) and that is 4.37 computer GB* where 1 kbyte is 1024 bytes* . DVD+R/DVD+RW and DVD-R/DVD-RW supports this format. Also called Single Sided Single Layered. This is the most common DVD Media, often called 4.7 GB Media.
DVD-10, holds around 9 400 000 000 bytes (9.4 GB) and that is 8.75 computer GB*. DVD+R/DVD+RW and DVD-R/DVD-RW supports this format. Also called Double Sided Single Layered.
DVD-9, holds around 8 540 000 000 bytes (8.54 GB) and that is 7.95 computer GB*. DVD+R supports this format. Also called Single Sided Dual Layered. This media is called DVD+R9, DVD+R DL (dual layer) or 8.5 GB Media.
DVD-18, holds around 17 080 000 000 bytes (17.08 GB) and that is 15.9 computer GB*. DVD+R supports this format. Also called Double Sided Dual Layered.
* In the computer world is 1 KB data = 1024 bytes so,
4 700 000 000 bytes / 1024
= 4 589 843KB / 1024
= 4482MB / 1024
= 4.37GB . (Return to Top)
5. Q : How come my 4.7 GB DVD isn't really 4.7 GB?
A : Like hard drives, 1 GB on a DVD recordable disc equals 1 000 000 000 (109) bytes. In contrast, a computer considers 1 GB to be 1 073 741 824 (230) bytes. Thus, a 4.7 GB disc is seen by a computer as having approximately 4.37 GB.. (Return to Top)
6. Q : How long does it take to burn a CD-R?
A : It depends on how much data you're going to burn, and how fast your drive is. Burning 650MB of data takes about 74 minutes at 1x, 37 minutes at 2x, and 19 minutes at 4x, but you have to add a minute or two for "finalizing" (sometimes known as "fixating") the disc. So, burning 700MB of data takes about 3 to 4 minutes at 52x with "finalizing" the disc.
If you have half the data, it will finish in (about) half the time.
Remember that single speed is 150KB/sec, double speed is 300KB/sec, and so on . (Return to Top)
7. Q : Video File Comparison
A :
| Format |
VCD |
SVCD (super VCD) |
DVD |
| Resolution NTSC/PAL |
352x240
352x288 |
480x480
480x576 |
720x480
720x576 |
| Video Compression |
MPEG1 |
MPEG2 |
MPEG2,
MPEG1 |
| Video bitrate |
1150kbps |
~2000kbps |
~5000kbps |
| Audio Compression |
MP1 |
MP1 |
MP1, MP2, AC3,
DTS, PCM |
| Audio bitrate |
224kbps |
~224kbps |
~448kbps |
| Size/min |
10 MB/min |
10-20 MB/min |
30-70 MB/min |
| Hours/DVD |
N/A |
N/A |
1-2 hrs |
| Hours/Dual Layer DVD |
N/A |
N/A |
2-4 hrs |
| DVD Player Compatibility |
Great |
Good |
Excellent |
| Computer CPU Usage |
Low |
High |
Very High |
| Quality |
Good |
Great |
Excellent |
The video quality depends on the bitrate and the video resolution, higher bitrate and higher resolution generally means better video quality but bigger file size
*Remark:
kbps = thousand bits per second
Mbps = million bits per second
~ approximately bitrate, it can be higher or lower
8. Q : What does "buffer underrun" mean?
A : The CD writing process can't be interrupted in mid-session. To prevent this from happening, the makers of CD recorders put a write buffer in the drive, usually 1MB or 2MB. Data read from the hard drive, tape, or another CD is stored in the buffer, and pulled out as needed by the recorder.
If the recorder requests data from the write buffer, but there's none there, it's called a buffer underrun. The disc is still spinning, but there's no data to write, so the recording process aborts.
Some advices for preventing buffer underruns are:
* Use a faster computer
* Record at a slow speed
- It takes longer to empty the buffer
* Don't do anything else with the computer while recording.
* Don't record on a file server!
* Defragment your Hard Disk
* Depending on your setup, putting the recorder and your hard drive on separate SCSI controllers may be necessary
* Turn off the screen saver . (Return to Top)
9. Q : What is CD-R?
A : CD-R is short for "CD Recordable". Recordable CDs are Write Once, Read Multiple media that work just like standard CDs. The advantage of CD-R over other types of optical media is that you can use the discs with a standard CD player.. (Return to Top)
10. Q : What is DVD+R and DVD+RW?
11. Q : What is DVD+R DL (dual layer)?
A : DVD+R DL or called DVD+R9 is a Dual Layer writeable DVD+R. The dual layered discs can hold 8.54 GB (called DVD-9) and dual layered double sides 17.08 GB (called dvd-18). (Return to Top)
12. Q : What is DVD-R and DVD-RW?
A : DVD-R was the first DVD recording format released that was compatible with standalone DVD Players. DVD-R is a non-rewriteable format and it is compatible with about 93% of all DVD Players and most DVD-ROMs. DVD-RW is a rewriteable format and it is compatible with about 80% of all DVD Players and most DVD-ROMs. DVD-R and DVD-RW supports single side 4.7GB DVDs (called DVD-5) and double sided 9.4 GB DVDs (called DVD-10). (Return to Top)
13. Q : What is DVD-RAM?
A : DVD-RAM has the best recording features but it is not compatible with most DVD-ROM drives and DVD-Video players. Think more of it as a removable hard disk. DVD-RAM is usually used in some DVD Recorders.. (Return to Top)
14. Q : What is ISO-9660 Standard?
A : * Level 1 ISO-9660
This defines names to be the familiar 8+3 convention that MS-DOS users have suffered through for many years: eight characters for the name, a period ("full stop" for those of you in the U.K.), followed by three characters for the file type, all in upper case. Many special characters (space, hyphen, tilde, equals, and plus) are forbidden. There's also a file version number, separated from the name by a semicolon, but it's often ignored.
* Level 2 ISO-9660
It allows longer filenames and deeper directory structures (32 levels instead of 8), but isn't usable on some systems, e.g. MS-DOS. . (Return to Top)
15. Q : What is Joliet?
A : Joliet is an extension of the ISO 9660 standard, developed by Microsoft to allow CDs to be recorded using long filenames, and using the Unicode international character set. Joliet allows you to use filenames up to 64 characters in length, including spaces. Joliet also records the associated DOS-standard name for each file so that the disc may be read on DOS systems or earlier versions of Windows.. (Return to Top)
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