From ISO/IEC 23001-7:2012/Amd 1:2012 10.2.2 Creation of Initialization Vector (Informative)
Decryption efficiency may be improved if subsequent initialization vectors use the value of the last cipher block at the end of the previous sample so that multiple samples may be decrypted as continuous chain.
The algorithm is AES-128-CBC.
My question is: Can this really be true?
My understanding of efficiency is decryption time. For each group of blocks where a new IV would be needed the only reduction in time would be the read time of the IV (assuming the last block is kept in memory to be used as IV). But this reduction would so small in comparison to the read+decryption time of the actual blocks that I wouldn't even mention it.
The size on the other hand would be reduced as many IVs are not needed. But this depends on how many blocks are in each sample.