First, what is a BUFFER UNDERRUN?
Music CDs and CD-ROMs are recorded with a data format so that they can
be mass-produced on a press mould. Whereas data is recorded to HDDs and
MOs uses physically short block with breaks in between the blocks, CDs
are recorded so that there are no breaks in the data from beginning to
end. Data has to be written in one go since data is written to CDs as
an essentially continuous line. Conventional CD-R/RW drives are designed
with that fact in mind, and accordingly leave a large gap on the CD if
data writing is stopped and then restarted. Even though CDs are said to
be very resistant to dust and scratches, if there is a gap in the data
it theoretically means that the data is lost, and will cause a reading
error in any CD player or CD-ROM drive. If for some reason, the data being
sent from the computer to the drive is late when writing takes place,
writing is temporarily stopped when the data runs out, thus causing an
error. This is called buffer underrun error. Once you get a buffer underrun
error on your CD, the CD can no longer be read and in most cases it renders
the CD useless. Buffer underrun errors occur easily with high-speed (on-the-fly)
writing directly from a hard disk or CD-ROM drive with a low data transfer
speed, or if some other application is being used on the computer while
a CD is being written. In contrast to the press molded music CD or CD-ROM
format, buffer underrun errors do not occur with the original packet write
system developed for recording with personal computers because data is
divided into packets.
BURN-Proof Features
The cause of Buffer Under Run Error 
In order to make CD-DA/CD-ROM compatible discs, it is required
to write the data constantly on the discs. However, data stream speed is
not always constant, especially when starting up some other applications,
such as the Internet. Further, if an unexpected error occurs in the source
disc, this will create the Buffer Under Run error. These are the typical
causes of a Buffer Under Run Error.[Fig-1]
Once a Buffer Under Run Error has occurred, the disc cannot be read by a
CD-ROM or in the worst case, the disc will be useless (i.e.,garbage).
[Fig-1] Without BURN-Proof Drive --------------->
----------------------------------------------------------------------------------------------------------------------------------------
The benefit to users of the BURN-Proof
technology
New technology now enables many CD-R/RW drives to record data seamlessly
between the end of one recorded point and the start of another recording
point, even though data transfer may be suspended due to the occurrence
of a Buffer Under Run Error.[Fig-2]
1. BURN-Proof technology helps prevent the creation of a useless disc
(coaster disc).
2. BURN-Proof technology allows the user to multitask on their PC. Previously,
a user couldn't do any other work on the PC while recording data. With
BURN-Proof technology you do not have to suspend your work even though
you are recording data.
3. Lower performance PCs may also perform high-speed recording. Actual
recording speed depends upon the data transfer rate of the PC and the
PC's performance.
SANYO named this technology "BURN-Proof".
Plextor uses Burn-Proof along side a technology developed by them called
PoweRec
II.
JustLink
works on the following principle
1. The amount data accumulated in the buffer memory is always monitored
during writing.
2. If, for some reason, the data transfer speed from the computer falls
below the writing speed, the amount of data accumulated in the buffer memory
falls.
3. When the amount of data in the buffer memory falls below a certain level,
and the possibility of a buffer underrun error is predicted if writing continues,
writing is intentionally suspended for the time being.
4. During the time that writing is suspended, data transferred from the
computer accumulates in the buffer memory.
5. When enough data has accumulated, writing is resumed from the point directly
after the point where it was suspended, and monitoring of the amount of
data in the buffer memory is recommenced.
Seamless Link
Acer
Products with Seamless Link
The Coolest Technology to Prevent Buffer Under Run Error !
From the beginning of recording process , the CD Recorder must first load
a certain amount of data into the buffer . The data buffer should always
be capable of holding enough data to guarantee continual data recording
on the CD-R/CDRW disc.
However due to the recording speed of CDR/CDRW drive becomes more and more
fast than ever before , in case the PC system can't deliver data at speed
which is fast enough to the recording drive, then the Buffer Under Run error
may occur.
This could be caused by a slow PC, slow hard drive or CDROM Drive, Multitasking,
network or interface problems, etc. This problem has become the major concern
for high speed CD-R/RW drive users.
The conventional CD-R/CDRW drive can't stop the recording process during
recording while the buffer under run error happened and re-start the recording
process while the data received again. The critical issue was how close
the gap between the stop and restart point could be controlled to let the
recorded data satisfy the standard and be read back without any problem.
The traditional solution for the buffer under run problem was: Enlarge the
buffer size to accumulate more data to prevent the error happened. But the
Seamless Link technology is a new function which is developed to prevent
the Buffer Under Run problem automatically by predicting them before they
happen.
The working principle of Seamless Link was list as following:
1. Monitoring the amount of data which buffered during writing.
2. Stop the writing process and store the RecEnd address if there is any
problem which causes the amount of data in the memory below a certain level
3. Waiting on the Pause state and receiving the new data to fill the buffer
memory
4. Seek to the in advance of RecEnd address to find the exactly RecEnd point
5. Re-Start the recording process
What is SafeBurn ?
SafeBurn is a trademark of Yamaha Corporation given for the recording protection
system that not only avoids buffer underrun, but ensures the written disc
is the best possible quality, even at the fastest of recording speeds. SafeBurn
is the comprehensive concept for Fast, Error-proof CD recording, which includes
(but not limited to) Buffer Underrun Protection, huge 8MB buffer and Optimum
Write Power Control.
That means triple security:
- 8 MB Buffer
- Buffer underrun protection
- Optimum Write Speed Control
8 MB Buffer
The frequent activation of buffer underrun protection extends the time required
for the completion of disc writing, because the drive has to seek for the
linking point every time. Too many occurrence of buffer underrun devaluates
the essential nature of high speed drives. In addition, even if buffer underrun
protection can make virtually seamless links, a disc with no link is obviously
better than one that is full of links.
Buffer underrun protection
The Buffer Underrun Protection packaged in SafeBurnT completely eliminates
buffer underrun errors. If data transfer is delayed and memory in the buffer
drops to a critical level, recording is suspended until the buffer has regained
sufficient memory, after which the writing restarts virtually seamlessly
from the point where it was suspended
Optimum Write Speed Control
The Optimum Write Speed Control function that automatically adjusts writing
speed to the optimum level for each kind of disc, removes user concerns
about recording speeds and the CD-R disc's compatibility. Simply by setting
the writing speed at 20X, the CRW2200 checks the characteristics and conditions
of the inserted disc and automatically selects the maximum optimum writing
speed for the disc to ensure data reliability when the disc is read back
by CD-ROM drives or CD players (like a foolproof camera detect the sensitivity
of the inserted film and adjusts the shutter speed).
ExacLinkT Buffer Under-run Technology
. ExacLink eliminates buffer under-run errors, the major cause of un-readable
discs.
. ExacLink allows error free high speed writing in slow PC systems.
. ExacLink leaves you free to browse the web or perform other tasks on your
PC while your CD is being recorded.
ExacLink allows trouble free creation of CD audio and other disc types under
the most difficult conditions. The ExacLink feature allows high speed, high
quality writing of discs on the first try, regardless of the computer performance
and drive buffer size. Buffer under-runs are no longer a problem with ExacLink
since the drive automatically responds to the condition and continues writing
as soon as more data is available without causing a buffer under-run error.
. ExacLink eliminates the need for larger drive buffer sizes.
The ExacLink feature allows the drive to pause the write operation when
data flow to the drive is interrupted due to other computer activity. When
the drive receives enough data to continue, it begins writing again at the
exact point where the previous write was stopped and with the exact power
level and frequency used during the previous write. In this way, it appears
to a reading device as if the writing operation had never been interrupted.
This feature is valuable for writing CD audio discs since without the ExacLink
feature, the drive would not be allowed to stop and re-start writing at
random times since the resulting disc would be unreadable or contain errors.
Shock
Proof BU
What is Shock-BP?
It is the record to CD-R media that the laser is irradiated in the organic
pigment of the record material, and a record mark (pit) is printed at
the high temperature of 300 degrees. This laser handles a servo control
of the lens so that it becomes the most suitable through the pick-up lens
for the record side of the disk..
As for 24X speed recording, the handling operation like
the drive on the highway by jet plane will be required. What will happen
if sudden side wind blows while it is moved at high speed ? If it is a
car, it will jump to the opposite lane. On the other hand, if the CD-R
recording is taken as an example, the overwriting on the recorded track
and the doodles on the unrecorded track will occur, and these problems
will lead to the failure of recording.
And so, Shock-BP monitors the condition of focus servo
and tracking servo and stop the recording with the memorizing of position
when it detects the rapid change in servo condition, then, it restarts
the recording at the stop position after the servo condition is recovered.
The portable CD-R/RW drive which is resistant to "the shock"
during the record was realized by this "Shock-BP" technology.
*The lens servo to focus this laser output on the record
side of the disk is generally called "focus servo", and the
lens to precisely trace the track engraved on the disk and the servo to
trace are generally called "tracking servo ".
*A impact to say here is about the impact when a tennis ball is dropped
from the height of 50cm
MORE
Power-Burn
Power-Burn is the technology designed to prevent errors
in writing data onto a CD-R/RW disk in a CD-R/RW drive by automatically
setting up the optimum recording conditions for the media while automatically
adjusting to the delay in data transmission from a host PC. Even if data
writing onto a CD-R/RW disk is interrupted due to delays in data transmission
from the host PC (buffer under-run), Power-Burn technology instantly controls
and accurately connects the interruption and resumption points of the
data recording to give continuous writing indispensable for CD-R/RW playback
compatibility.
In addition Power-Burn automatically optimizes recording
conditions for the CD-R/RW drive such as the writing speed and the strength
of recording laser light,analyzing the disk quality by reading pre-recorded
information like the recommended recording speed and the conditions of
a recordable side of the disk. In general, the acceleration of writing
speed of CD-R/RW drives increases the possibility of delay in the data
transmission from the host PC, which causes buffer under-run. Because
CRX175A stops its data transmission when buffer under-run occurs and resumes
writing only after a sufficient amount of data has been transmitted from
the host PC, it avoids writing errors.
