MOTIVATION: Recent advancements in sequencing technology have led to a drastic 
reduction in the cost of sequencing a genome. This has generated an 
unprecedented amount of genomic data that must be stored, processed and 
transmitted. To facilitate this effort, we propose a new lossy compressor for 
the quality values presented in genomic data files (e.g. FASTQ and SAM files), 
which comprise roughly half of the storage space (in the uncompressed domain). 
Lossy compression allows for compression of data beyond its lossless limit.
RESULTS: The proposed algorithm QVZ exhibits better rate-distortion performance 
than the previously proposed algorithms, for several distortion metrics and for 
the lossless case. Moreover, it allows the user to define any quasi-convex 
distortion function to be minimized, a feature not supported by the previous 
algorithms. Finally, we show that QVZ-compressed data exhibit better performance 
in the genotyping than data compressed with previously proposed algorithms, in 
the sense that for a similar rate, a genotyping closer to that achieved with the 
original quality values is obtained.
AVAILABILITY AND IMPLEMENTATION: QVZ is written in C and can be downloaded from 
https://github.com/mikelhernaez/qvz.
CONTACT: mhernaez@stanford.edu or gmalysa@stanford.edu or iochoa@stanford.edu
SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics 
online.