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The Audio Options from Blu-ray
Because Blu-ray disks have a higher capacity than DVDs, they can offer higher resolution sound and pictures. In order to fit six channels of sound onto a DVD, the channels are compressed. These formats are the familiar Dolby Digital 5.1 format and DTS 5.1. Blu ray offers the opportunity to include more audio information, allowing more channels and lossless compression techniques to be used which allow the signal to be reconstructed with no loss of quality compared to a signal stored with no compression. As with DVDs, there are competing Dolby flavors (Dolby Plus or True HD) and DTS flavors (HD HD-Master Audio).
Whilst all modern players support these formats, only selected players offer the facility of decoding the audio in the player and outputting the signal as analog audio via 6 or even 8 RCA phono cables. The rest will pass the high resolution digital audio signal out via the HDMI lead along with the digital video for decoding in your receiver
If the highest quality audio cannot be decoded, then you will have to settle for DVD quality output. This may be achieved via a coaxial or optical digital audio cable as well as via multiple analogue RCA phono leads.
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The Connection Options from Your Blu-ray Player to Your Home Theater Receiver
There are four ways to connect your Blu-ray player to your home theater receiver for audio purposes. Generally, the simplest and best is an HDMI lead. This carries high quality digital video and audio signals in one combined lead.
Some Blu-ray players will offer six analog RCA phono outputs for 5.1 sound, or eight phono outputs for 7.1 sound. Provided that your player will decode the high quality digital format, this method can transmit this quality even if your receiver does not offer high quality decoding itself. There may be some degradation due to analog transmission or, in the worst case, transmission of the DVD quality Dolby Digital soundtrack where the player does not have the facility to decode the highest quality audio.
The other two methods of connection are digital audio coaxial and optical connectors. These generally are limited to the Dolby Digital soundtrack.
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What Happens When the Audio Reaches the Receiver?
What happens when the audio signal reaches the receiver depends largely upon the age of your receiver. In 2009, state of the art £1000/$1500 receivers come with up to 6 HDMI inputs. When connected to a state of the art Blu-ray player, you can connect it with an HDMI lead, pass the signal digitally along the cable and expect the receiver to decode the highest quality audio format for the best possible quality. Even budget receivers will offer multiple HDMI inputs capable of handling digital video and audio signals and the only requirement is to ensure that the audio is transmitted at the highest possible quality.
However, many of us have slightly older equipment to which we wish to add a Blu-ray player. For example, personally my receiver is about 18 months old. It was a highly regarded £300/$450 receiver at the time it was bought. It has 2 HDMI inputs which can be switched to transmit the video signal from my DVD player or my cable box to the TV. The receiver does not handle audio signals via the HDMI input. The solution here is to buy a Blu-ray player that handles audio decoding internally and can output the decoded audio via analog 5.1 RCA phono inputs to your receiver. You will need to check that your Blu-ray player of choice has the required analog outputs. Some older Blu-ray machines have the analog connections but decode only at lower resolutions.
If, however, like me, you enjoy high quality multichannel music from SACD or DVD Audio disks, your multichannel audio inputs may be already occupied. Sadly in such cases, an upgrade from DVD to Blu-ray may also require a new receiver or a complex and unwieldy 5.1 switching box and a total of 18 cables to take advantage of high quality audio as well as high quality video.