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Constant linear velocity
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<p>In <a href="/facts/Optical_storage/D2rM4VkH">optical storage</a>, constant linear velocity (CLV) is a qualifier for the rated speed of an <a href="/facts/Optical_disc_drive/IM9ugGbU">optical disc drive</a>, and may also be applied to the writing speed of recordable <a href="/facts/Optical_disc/vjVDB1GH">discs</a>. CLV implies that the <a href="/facts/Angular_velocity/2n8JljAT">angular velocity</a> (i.e. <a href="/facts/Revolutions_per_minute/fdNmLToF">rpm</a>) varies during an operation, as contrasted with <a href="/facts/Constant_angular_velocity/MIFTgq2k">CAV</a> modes. </p><p>If the data density is the same everywhere on the disc, as is the case with <a href="/facts/Compact_Disc/g51GRloc">CD</a> and <a href="/facts/DVD/7fJsHJrN">DVD</a> and <a href="/facts/Blu-ray_disc/zyPalhfG">Blu-ray discs</a>, the linear velocity directly correlates with the transfer rate (read speed or write speed), meaning an increase in linear velocity also increases the amount of data read from the disc in the same time, regardless of whether the laser is reading from or writing to the inner edge or the outer edge of the data area. At any disc rotation speed (angular velocity), the linear velocity is higher at the outer edge than at the inner edge of the disc, given that the outer edge travels a longer distance. </p><p>The concept of constant linear velocity was patented in 1886 by phonograph pioneers <a href="/facts/Chichester_Bell/bBfJGDxc">Chichester Bell</a> and <a href="/facts/Charles_Tainter/gTAM3bRx">Charles Tainter</a>. </p>