HD sound: a new world of quality
For a long time, for movie lovers, the combination of quality video and sound was almost impossible.
For many years, the best that could be achieved was a VHS cassette sound, which was monaural with limited quality. Only with the arrival of Hi-Fi VHS in 1985, the cassettes acquired good quality stereo sound and even the possibility of surround sound through Dolby Pro Logic decoding. However, this luxury came at a price, as the first high-fidelity VHS recorders sold for more than $ 2,500 on the market. However, only the LaserDisc provided high-quality video to a wide mass of consumers: a laser disc with a diameter of 30 cm could fit up to an hour of video per side, along with digital stereo sound, which could be transformed into three-dimensional sound after Dolby Pro Logic decoding. But the life of the LaserDisc was short lived, as they have given way to much less bulky DVDs with Dolby Digital (5.1) sound. I must say that Dolby Digital appeared on some versions of the LaserDisc, but expensive equipment was required to reproduce it.
The DVDs appeared in 1997 in the United States and in 1998 in Europe. Over the years, they have won over the majority of moviegoers and home theater enthusiasts, after which the general public has taken an interest in them. In addition to much better picture quality compared to traditional VHS cassettes, the discs allowed you to select one of several surround sound tracks (Dolby Digital and often DTS), optionally display subtitles, making it possible to watch a movie. with the original soundtrack. This is very important for the sound, as dubbing often distorts the original soundtrack, even if it is superimposed very carefully, which is also rare. After years of service, the DVD format is leaving the scene, giving way to HD-DVD and Blu-ray. As is common in times of major change, many questions arise ranging from technical difference to areas of use. And the answers are not always as obvious as we would like.
Maintaining compatibility
Maintaining compatibility
Viewers will immediately begin to highlight compression and loss of surround sound standards, which they believe has a serious impact on quality. But not all is so easy. Of course, lossy compression is bad, but our world is not binary. During the long process from shooting a movie to playing it in the living room, quality loss occurs much more frequently than most users realize. In either case, the quality of the playback depends in part on the available bitstream. The Dolby Digital standard, which is the main standard for DVD, provides a transmission of up to 448 kbps, in HD-DVD it reaches only 504 kbps and the absolute limit is 640 kbps. Therefore, for a higher flow, it is necessary to change to another standard. So Dolby Digital Plus streaming can be up to 3 Mbps by current standards, but its maximum level is 6 Mbps. Surround sound standards include DTS with a 768 kbps to 1.5 Mbps stream on DVD. In theory at least, since DTS didn’t appear in every movie. But two versions of DTS-HD go even higher.
Dolby and DTS were carefully designed in the transition to high definition to maintain compatibility with existing equipment (in particular, home theater systems), as the fleet cannot be magically changed and cinema systems at home Full HD will remain for a long time. in minority. Therefore, HD formats must provide streaming in accordance with the surround sound standards that this home theater system can decode. In any case, the quality of high-definition discs is superior to that of DVDs, and the original disc is recorded in high quality. In addition, compatibility with other transmission media (cable, satellite and terrestrial television) should be considered, as well as possible developments such as video on demand.
