Digital Trends

Philips HDRW720

April 11th, 2005 | by Dennis Barker

Introduction

Philips developed DVD Plus ReWritable (DVD+RW) for both data and video content as well.  Even though it uses a different recording method, it has been designed to work with DVD-ROM, and is also backwards compatible with most current DVD video players on the market today.  The DVD+RW format uses two types of discs: single-sided discs with a capacity of 4.7GBs, and dual-sided ones with a capacity of 9.4 GBs.  There are several recording speeds, ranging from a high quality (HQ) standard play (SP) mode of one hour with an image resolution of 500 lines, up to an extended play (EP) mode of up to eight hours at an image resolution of 250 lines per side. 

Philips' DVD+RW video technology is encoded in MPEG-2 with a variable bit-rate, which provides higher bit-rates as necessary so that no storage capacity is wasted; this allows for the optimum allocation of bits on the disc.  In real-time video applications, it makes a provisional analysis of the input video, creating a target bit-rate that is typical for a selected playing time or level of video quality selected.  Since DVD+RW uses a variable bit-rate, it can create longer recording times (up to eight hours) with superior image quality.  Maximum recording can be further improved by using a "lossless linking" technique.  Lossless linking simply means that there are no large blank spots on the disc, which can be up to 2kB wide between different video segments.  This technique allows the writing process to be stopped or suspended, and then resumed without making the discs incompatible with other machines.  Additionally, lossless linking makes it possible to replace any individual 32 kB (kilo byte) block (or recording unit) by a new one without losing compatibility with other DVD players or DVD-ROM drives.

Philips HDRW720

DVD+RW video discs contain one or multiple menus (still images of recordings) that give information about each recording such as playing time, program name, data and time or recording, quality level, and a key frame display representing a recording (still image.)  The DVD+RW video recorder generates or updates the menus immediately after a recording has been completed.   DVD+RW discs offer complete interchangeability between home recorders and PCs with DVD+RW drives so that material can be edited on a home computer and then played back on a home deck.  Blank single-disc 4.7GB discs cost about $.72 for DVD+R and $1.99 or less for DVD+RW.

DVD+R is a “write-once” format that shares many of the same attributes as DVD+RW.  It is impossible to erase or overwrite a DVD+R disc.  Like DVD-R, DVD+R allows for home videos to be recorded so that they cannot be accidentally erased at a later time.  DVD+R is 100-percent compatible with Philips DVD players that playback DVD+RW, and 85-percent compatible with Panasonic and Pioneer DVD players that playback DVD-R.  In terms of editing, DVD+R discs can be edited until finalized, whereas a DVD-R disc cannot be altered after being recorded.  According to Philips, it will only take about 1-minute to finalize a DVD+R disc, but it can take between 4-minutes and 15-minutes for a DVD-R disc to be finalized.   Philips also notes that you can change Picture Indexes and apply Favorite Scene Selection to DVD+R, but cannot with DVD-R.