The Transfer rate test measures the read speed of data, i.e. the speed at which data is read from a disc. If the disc inserted is blank, the test measures the write speed.
This test is suitable for testing an optical drive and for verifying the readability of burned discs (CDs or DVDs).
The results are displayed in the form of two curves in the graph. By default, the read speed is shown as a green line, and the rotational speed or angular velocity of the disc is shown as a yellow line.
The horizontal scale shows the storage capacity values (in MB for CD’s and in GB for DVD’s). The vertical scales show the read speed on the left and the rotational speed on the right in RPM x 1000.
With a dual layer disc, the graph shows two additional vertical lines: a red one for the full capacity of the disc and a pink one that divides the representation into two sections. Each section shows the measurement for one layer.
In addition, the test results are displayed in the Speed area, to the right of the graph.
The following display panels are available in the Speed area:
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Current/Average
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Shows the varying speed over the course of the test. The average speed is displayed here when the test is finished.
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Start
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Shows the lowest speed determined over the course of the test. In a normal curve, the lowest speed is also the start speed. In an uneven curve, the lowest recorded speed is displayed here as the minimum value.
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End
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Shows the highest speed determined over the course of the test. In a normal curve, the highest speed is reached at the end. In an uneven curve, the highest recorded speed is displayed here as the maximum value.
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Type
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Shows the type of rotational speed.
A disc can be read with the following types of rotational speed:
CAV (constant angular velocity): With constant angular velocity, the disc rotates at a constant speed, which means the inner tracks travel at the slowest linear velocity. The linear velocity increases as you move away from the center towards the outer edge. The data rate remains constant while the data density decreases away from the center of the disc.
CLV (constant linear velocity): With constant linear velocity, the rotational speed of the disc decreases as the laser moves away from the center of the disc. As a result, both the read speed and the data density and rate remain constant in all areas of the disc.
ZCLV (zone CLV): If a disc is divided into several CLV zones, each one of them can be read and above all burned as separate logical areas by using CLV. 16x speed is a characteristic value for the innermost zone of a CD, after which the speed can be increased in stages.
PCAV (partial CAV): In a combination of CAV and CLV, CAV technology is used in the inner area of the disc. When a certain linear velocity is reached, CLV technology is switched to towards the outer edge of the disc. In other words, the rotational speed remains constant until the read speed has reached a maximum value; the read speed then remains at a constant level while the rotational speed decreases.
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See also
| Rotational speed |
Discs can be read and/or burned in different ways. As a general rule, the reading process in optical drives starts at the radius of the disc and moves from the center outwards. The two standards used to define the types of rotational speed are linear velocity and angular velocity. With constant angular velocity, the tracks at the center of the disc always travel at the slowest linear velocity. The linear velocity increases as you move away from the center towards the outer edge. Angular velocity (also called rotational speed) describes the change in the rotation angle over time independently of the radius of the disc, i.e. the velocity at which an object loops a sector.
| Read Speed |
The read speed of a drive is a factor of the speed that the laser needs in order to read the data on an optical storage medium, e.g. 8x or 16x speed.
| RPM |
Revolutions per minute (RPM) is an English unit that is used in mechanics to represent rotational speed. It indicates the number of complete revolutions per minute.
| Dual Layer Disc |
A dual layer disc refers to a DVD that uses two layers on one side, which increases its storage capacity.
| Write Speed |
The write speed indicates the speed at which a drive can write data to the optical storage medium, e.g. 8x or 16x speed.