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Author Topic: What actually comes out of the "coax" output of a Blue Ray player?  (Read 9242 times)

kristianjohnsen

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Having recently saved the day by having a free SPDIF-port to connect a Blue Ray player to, I started thinking about what actually travels out of the connector on the player, just labelled "coax".

I received stereo information just fine, but had I connected the same output to a home stereo system I believe it would have read 6 discrete channels?

Or is it 6 discrete channels plus stereo?  (And the stereo channels are streamed in a manner that a two-channel device will only see the stereo information, and just disregard the others?)

Or is it just stereo audio alonside decoding information used to separate the audio into discrete channels?

Or something completely different?

Thanks in advance for any insight!
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Mac Kerr

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Re: What actually comes out of the "coax" output of a Blue Ray player?
« Reply #1 on: April 03, 2015, 06:05:42 pm »

Having recently saved the day by having a free SPDIF-port to connect a Blue Ray player to, I started thinking about what actually travels out of the connector on the player, just labelled "coax".

I received stereo information just fine, but had I connected the same output to a home stereo system I believe it would have read 6 discrete channels?

Or is it 6 discrete channels plus stereo?  (And the stereo channels are streamed in a manner that a two-channel device will only see the stereo information, and just disregard the others?)

Or is it just stereo audio alonside decoding information used to separate the audio into discrete channels?

Or something completely different?

Thanks in advance for any insight!

It is a stereo signal that that the multichannel information encoded. In a stereo receiver it would be decoded into 5.1 or whatever other multichannel format was included.

Mac
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kristianjohnsen

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Re: What actually comes out of the "coax" output of a Blue Ray player?
« Reply #2 on: April 03, 2015, 06:25:10 pm »

It is a stereo signal that that the multichannel information encoded. In a stereo receiver it would be decoded into 5.1 or whatever other multichannel format was included.

Mac

Thanks, Mac, that makes perfect sense! 

I remember in the days of VHS, there was Dolby Pro Logic that could sortof extract surround sound from a stereo signal, but when DVD came, many people wanted players with discrete outputs for each channel to inject into the "multichannel input" of their home cinema receivers, making for vastly surperior channel separation.

Do you know if there is a similar situation with decoding the "coax" output of a Blue Ray vs using a player with a separate outputs for each channel?

Also, do you know if a player with an optical output, outputs the same stereo signal with decoding information as the electrical counterpart, or does it output separate channels much like an ADAT-data stream?

What would happen if one connects the optical output to the ADAT port of a mixer?
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Alex Donkle

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Re: What actually comes out of the "coax" output of a Blue Ray player?
« Reply #3 on: April 03, 2015, 07:00:27 pm »

Thanks, Mac, that makes perfect sense! 

I remember in the days of VHS, there was Dolby Pro Logic that could sortof extract surround sound from a stereo signal, but when DVD came, many people wanted players with discrete outputs for each channel to inject into the "multichannel input" of their home cinema receivers, making for vastly surperior channel separation.

Do you know if there is a similar situation with decoding the "coax" output of a Blue Ray vs using a player with a separate outputs for each channel?

Also, do you know if a player with an optical output, outputs the same stereo signal with decoding information as the electrical counterpart, or does it output separate channels much like an ADAT-data stream?

What would happen if one connects the optical output to the ADAT port of a mixer?

Coax (SPDIF) typically outputs either DD or DTS 5.1 channel digital encoding, or PCM 2.0 channel digital encoding. This is typically auto-selected by the AV receiver. For reference, SPDIF is just a consumer version of AES3 digital audio.

Using the coax output means the AV receiver will decode the 5.1 surround signal, vs. the Blu-Ray playing using it's own decoder. No real difference between the two options, although generally it's best to keep the signal digital (i.e. coax) as long as possible.

Blu-Ray player optical outputs are typically TOSLINK, not ADAT. Identical digital signal to the coax. No difference between the two.
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kristianjohnsen

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Re: What actually comes out of the "coax" output of a Blue Ray player?
« Reply #4 on: April 03, 2015, 07:26:18 pm »

Coax (SPDIF) typically outputs either DD or DTS 5.1 channel digital encoding, or PCM 2.0 channel digital encoding. This is typically auto-selected by the AV receiver. For reference, SPDIF is just a consumer version of AES3 digital audio.

Using the coax output means the AV receiver will decode the 5.1 surround signal, vs. the Blu-Ray playing using it's own decoder. No real difference between the two options, although generally it's best to keep the signal digital (i.e. coax) as long as possible.

Blu-Ray player optical outputs are typically TOSLINK, not ADAT. Identical digital signal to the coax. No difference between the two.

Hi Alex.

Thank you, this is just the information I was looking for!:)

Also, do you know what the difference is between TOSLINK and ADAT?  Will one work with the other?
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Mac Kerr

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Re: What actually comes out of the "coax" output of a Blue Ray player?
« Reply #5 on: April 03, 2015, 07:43:46 pm »

what the difference is between TOSLINK and ADAT?  Will one work with the other?

TOSLINK is a 2 channel optical digital format using visible red light over generally plastic fiber developed by Toshiba. ADAT is an 8 channel format developed by Alesis for their 8 track digital tape recorders using the same hardware.

Mac
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Brian Jojade

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Re: What actually comes out of the "coax" output of a Blue Ray player?
« Reply #6 on: April 04, 2015, 03:04:20 am »

SPDIF can transmit 2 channels of uncompressed digital audio. When used as 5.1 or 7.1 audio, the data that is transmitted is compressed first.  Compressed digital isn't better than good analog.
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Brian Jojade

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SPDIF can transmit 2 channels of uncompressed digital audio. When used as 5.1 or 7.1 audio, the data that is transmitted is compressed first.  Compressed digital isn't better than good analog.

I don't know about Blu Ray, but my understanding of this in a DVD context, is that the analogue outputs on my DVD player for 5/6/7.1 discrete video audio are derived using the same process as if I send an S/PDIF signal to an external AV processor.

The potential differences in quality result from differences between the quality of D/A conversion in whatever device.

Multi-channel video audio is read directly from the disk in the same compressed format which is then transmitted digitally via coax or optical. Does Blu Ray differ in this respect?


My best recollection is that most DVD players only offered a stereo analogue output. However accessing 5.1 output from  DVD-Audio or SACD requires separate analogue outputs on the DVD player, as the higher bitrate signal could only be carried in stereo via S/PDIF (similar to the limitation of a stereo digital PCM signal such as a compact disc).

My own DVD player (which plays DVD-A and SACD too) will only output a stereo digital signal for the high-res audio formats. There is no option to send a compressed digital multi-channel signal. I don't recall any DVD-A or SACD machine offering this - an analogue connection to the AV processor is the only choice.

Am I right in thinking DVD players do not actually compress signals to transport them digitally, but merely allow already-compressed signals to pass that way?


Apologies for the topic swerve, I have yet to upgrade to a Blu Ray machine. However I'd be very interested to learn the differences from DVD, especially the native audio processing and transport details.

Sent from my GT-I8160 using Tapatalk 2

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paul bell

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After reading the first post/opening question, I figured the "coax" jack was a yellow RCA which would make it an old school composite signal.
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Hayden J. Nebus

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I don't know about Blu Ray, but my understanding of this in a DVD context, is that the analogue outputs on my DVD player for 5/6/7.1 discrete video audio are derived using the same process as if I send an S/PDIF signal to an external AV processor.

The potential differences in quality result from differences between the quality of D/A conversion in whatever device.

Multi-channel video audio is read directly from the disk in the same compressed format which is then transmitted digitally via coax or optical. Does Blu Ray differ in this respect?


My best recollection is that most DVD players only offered a stereo analogue output. However accessing 5.1 output from  DVD-Audio or SACD requires separate analogue outputs on the DVD player, as the higher bitrate signal could only be carried in stereo via S/PDIF (similar to the limitation of a stereo digital PCM signal such as a compact disc).

My own DVD player (which plays DVD-A and SACD too) will only output a stereo digital signal for the high-res audio formats. There is no option to send a compressed digital multi-channel signal. I don't recall any DVD-A or SACD machine offering this - an analogue connection to the AV processor is the only choice.

Am I right in thinking DVD players do not actually compress signals to transport them digitally, but merely allow already-compressed signals to pass that way?


Apologies for the topic swerve, I have yet to upgrade to a Blu Ray machine. However I'd be very interested to learn the differences from DVD, especially the native audio processing and transport details.

Sent from my GT-I8160 using Tapatalk 2

On both platforms, when you use the stereo RCA outs on your player, you're getting a 2 channel mixdown of decoded multichannel audio.

On most DVD players there is a digital out (SPDIF/ TOSLINK) which you can set to be a PCM output (stero mixdown) or bitstream (unencoded multichannel)

Blu ray has native support for lossless multichannel codecs. There are DTS and Dolby flavors supporting 8 or more discrete channels. SPDIF will not support the data rate of this encoded bitstream, but HDMI will. To the extent your bluray player allows, You can decode the stream at the player and pass multichannel PCM over HDMI to a receiver, or you can send the encoded stream over HDMI, or you can mix it to stereo locally at the player and send that out HDMI - or use the analog/ SPDIF stereo outs- which will be a 2 channel mixdown.

 

 

     

 
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