Feurio Questions & Answers - Explanation of
Terminology:
On-the-fly copy
If an "on-the-Fly" copy is made, the data is read in directly from the CD-ROM
during the copying process. This has the great advantage that you do not have
to make a copy of the CD on the harddisk first. This saves time and also does
not require memory space on the harddisk for copying the CD.
In contrast to this, when making an "Image
copy", the CD is first read completely and then the burning process is started.
Advantages of an on-the-fly copy: - It is faster than an
"Image copy" -> The burning process can
be started without first having to wait for the end of the reading process
- No
harddisk memory is required to store the data.
Disadvantages of an on-the-fly copy:
- Read errors / uneven transfer from the
CD-ROM:
When recording an audio CD (as already frequently mentioned), the data has to
be sent to the CD writer continuously. If, e.g. the CD is slightly scratched,
most CD-ROMs automatically reduce the read speed and often automatically make
a repeat attempt to read. This causes the transfer rate to be temporarily reduced.
If the errors are "minor", this can be equalized out by Feurio!®'s buffer.
If, however, the read rate falls below the write rate for a longer period of
time, then the buffer is not filled up fast enough so a Buffer-Underrun occurs.
Incorrigible read errors: If incorrigible read errors
occur, then the read routine usually stops with an error message. In the case
of an on-the-fly copy, this would of course lead to a defective CD-R. For this
reason Feurio!® does not emit any error message in burning mode. Then
the data is written which it was possible to read. As a general rule, you will
then be able to hear a minor or major interruption on the copy, but the copy
will run. As the end of the copy process a message will appear to inform you
if incorrigible read errors have occurred.
Usually however, read errors lead to a Buffer-Underrun, as the CD-ROM usually
automatically make a repeated reading attempt and can thus no longer fill the
buffer.
- Uneven reading from CD-ROM (Jitter):
With an on-the-fly copy, the CD-ROM has to be able to read the data more quickly
than the CD writer writes the data. However this means it is not possible to
read data continuously from the CD-ROM. During reading, a pause often has to
be made in which it waits until there is space in the buffer again.
Some CD-ROMs just about manage to supply error-free data during a continuous
transfer. But if the transfer is interrupted, then often faulty data is read:
- Spindown:
CD-ROMs stop the rotation of the CD after a certain length of time without access.
"Starting up" the CD again takes a certain amount of time and several drives
provide faulty data during run up (in particular several Pioneer drives are affected
by this).
Under "Program Parameters", index card "CD-Copy" several measures can be taken
against the spindown. Reading from a drive which supplies faulty data during
the run up however continues to be a risk!
- Jitter:
Many CD-ROMs have problems finding exactly the same position again if continuous
transfer has been interrupted. Feurio!® tries to correct this error but this
is not always a resounding success.
In simulation mode you get an error message if it has not been possible to carry
out jitter correction successfully. In burning mode the data is burned anyway,
but it will then be possible to hear an error on the CD.
For more information see chapter: "Jitter".
- CD-ROM and Writer can block each
other:
If an IDE-CD-ROM and an IDE-CD-Writer are connected to the same IDE-Port, then
they hinder each other's access. (see: "SCSI vs.
IDE-CD-Writer").
- The CD-ROM drive is "blocked" for the whole
duration of the copy process.
- If further copies are to be burned, the original
CD has to be inserted again
Summary:
For an "on-the-Fly" copy, as the source you should only use a CD-ROM which has
"passed" the Device-Test of the Feurio!® CD-Manager.
Many CD-ROMs, which do not "pass" the Device-Test without an error may of course,
may be used for reading out normally; as already mentioned, the problems generally
only occur if the read process is interrupted. With an "on-the-Fly" copy however,
the read process is continually interrupted so that higher requirements are made
of the CD-ROM. Read errors also create a defective CD-R!
So "on-the-Fly" copy should only be used if e.g. there is no room on the harddisk
for an image. Making a copy via an image file is always much, much safer!
See also:
Questions and Answers - Explanation of terminology
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