Lossless linking

In the DVD+RW Video format, video can be encoded with a variable bit-rate (VBR). Because the writing process takes place at a constant bit rate, the writing process needs to be suspended and continued frequently. Normally, this would result in a linking loss, making the disc incompatible with read-only devices like DVD Video players and DVD-ROM drives. With DVD+RW it is possible to perform lossless linking, i.e. to suspend and continue the writing process without linking loss.

This feature makes the format very efficient and suitable for random write in data as well as video applications. Additionally, lossless linking makes it possible to replace any individual 32 kB block (recording unit) by a new one, without losing compatibility. For lossless linking it is necessary to write any data block in the correct position with high accuracy (within I micron). For this purpose the groove is mastered with a high wobble frequency (817 kHz at n= I), which ensures that the writing can be started and stopped at an accurately defined position. The writing clock as obtained from this groove is very accurate. At the same time, address information is stored in this wobbled groove by locally inverting the sign of the wobbled waveform. For each ERCO block, which is 32 kB, four addresses exist, resulting in a reliable address format with large detection margins.

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