Surround Sound in TV



 50” televisions don’t seem to cut it anymore. People seem to brag more about their surround sound in their home cinema system, more than the actual TV. Home Cinema system is basically a large TV, with surround sound. With broadcast surround sound, we look to the 1980’s where the first stereo broadcast was in 1986. Audio was behind the times in broadcasting compared to the commercial sector for the demand wasn’t high for better quality audio in television. Then, as with most things audio related, along came Dolby with their invention of Dolby Surround in 1982. This was a three channel system and was upgraded to Dolby Pro Logic in 1987 which had four channels, the extra channel usually held dialogue so it was separate from the other audio. Home surround sound went digital in 1995, only three years after cinema thanks to the invention of Dolby Digital Laserdisc. Similar to the cinema system, it provided 5.1 audio for those with systems that were capable of this. It mainly grew in 1997 when the first Dolby Digital DVD was released, making it more accessible to the general public. The other possible format for the audio to come in was DTS (Digital Theatre Systems) which was rare, but considered better quality than Dolby Digital. However DTS hardly caught on, and even though DVD players had to be able to decode DTS, it wasn’t used very much.

 DVD was the format of choice until Blu-Ray came along. It’s called Blu-Ray because it uses a violet laser to read the disc, rather than the red laser of DVD. The colour violet has a smaller wavelength than red, meaning they can store a lot more on Blu-Ray discs as the laser reads a vastly smaller amount of the disc. Blu-Ray was founded in 2002, but it wasn’t till 2006 where the first Blu-Ray discs came out. It took a while to catch on, as people needed to by a new player for the Blu-Rays. Blu-Ray had main competition from HD DVD, similar to Blu-Ray but developed by Toshiba. This section could easily be about how HD DVD is the format we use and how we nearly had something called Blu-Ray, but thanks to movie distributors siding with Blu-Ray and the announcement that Sony would be making their new console, Playstation 3, able to read and play Blu-Rays. This meant Blu-Ray won the war, and HD DVD was scrapped in 2008.

 Back in DVD, Dolby Digital came in a range of bit rates, ranging from 192kbps (considered poor) to the maximum 448kbps, which was used on most 5.1 soundtracks. DTS offered higher bit rates, which is why it was considered better quality audio. It could provide 754kbps, which was mainly used, but sometimes it provided 1.5Mbps. This is three times higher than the maximum of DVD, meaning that less data is lost when it is encoded, which should provide a better audio experience, however this is balanced with audio taking up a large chunk of the data available which can have an effect on the video quality.

 With Blu-Ray, there are a large number of formats that audio can come in. Dolby Digital and DTS are back! They slightly improved these formats to give them a better sound on the output of the disc, thanks to the larger space on Blu-Ray.

 First of the new audio formats is Dolby Digital Plus. This is, as you might guess, a better version of Dolby Digital, which has increased bit rates of up to 6Mbps which is considerably high than before, and can also support 7.1 surround sound. The next new format is DTS-HD High Resolution which can also provide 7.1 and up to 6Mbps bit rate. DTS-HD High Resolution does provide 24 bit audio resolution rather than just the 20 of Dolby Digital Plus.

 PCM is a different kind of audio as it is not compressed making it an exact replica of the studio master. This keeps all the audio as it was and therefore shouldn’t have lost any in the final outcome. It’s possible to have up to 24 bit resolution, but to save space, producers will probable downgrade it to 16 bit audio, which wouldn’t make much of a difference and save on bandwidth.

 The previous formats (except PCM) were all lossy compression formats, which as we know from earlier, take out some of the frequencies that, generally, humans cannot hear. The next lot of formats are all lossless compression. The next format is Dolby TrueHD, which is similar to PCM, but is compressed to save space on the disc. When it gets decoded it is identical to the studio master. ‘It may help to think of it like a ZIP file that holds a PCM track. Once you unZIP the file, you get a 100% identical copy of the original PCM, without compromising any sound’. (http://www.highdefdigest.com) The next format is the DTS equivalent of Dolby TrueHD, DTS-HD Master Audio. This is again similar to Dolby TrueHD, but the audio track takes up more room on the disc. To make up for this however, it does not need the backup track that Dolby TrueHD needs, so it makes up ground there. Ultimately, DTS-HD Master Audio isn’t used very much in Blu-Rays, but it is a possibility.

 One big advantage for Dolby TrueHD and DTS-HD Master Audio are the sample rates these use. Your standard format uses 48 kHz as a sample rate, but these formats can both support up to eight channels of 96 kHz/24-bit audio (meaning you can have 7.1 surround sound) and six channels of 192 kHz/24-bit audio (you can have 5.1 surround sound). This is a vastly higher sampling rate than anything else can offer, which is why these new technologies make the future look so exciting. Unfortunately, they are not supplied on every Blu-Ray and not everyone has the sound systems to listen to the audio in its truest form. This is something the will hopefully be rectified in the future.