In 1999, Sony introduced a format called SACD. To date, it is the highest quality audio readily available to the consumer. It has a data rate of 4 times that of a conventional CD. Other advantages involve the absence of filters used both in the recording and playback of conventional CD data. It is a high frequency one-bit format that behaves much as an analog recording would, but without the noise. All SACD format discs today are made as "hybrid" discs. They will all play normally on any regular CD player. An extra semi-transparent layer is accessed only by players capable of SACD playback. A true SACD player will use a digital to analog converter especially designed for "direct stream digital", or "DSD" formatted audio. More common SACD compatible players will downsample digitally and use conventional digital to analog conversion, albeit at a higer resolution setting than CD. Nearly all SACD releases include a surround sound 5.1 playback option. Unlike conventional movie releases, there is no lossy compression, such as Dolby surround or DTS. All channels are at full resolution. The SACD layer of a hybrid disc uses technology similar to a DVD, which allows almost 7 times the data of a regular CD allowing for all the extra information. The increased high frequency response and dynamic range along with surround allow for a truer reproduction of a concert hall environment. The overall effect is amazing for those willing to make the investment. Another feature of the SACD format is that it is still impossible to make a digital copy of the disc, ensuring copyright protection. High-res releases in conventional PCM audio have been slow in coming, partly due to concerns about releasing a master-grade recording to the public that can be copied easily.