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Author Topic: Two channel PCM and sound  (Read 4126 times)

thane108

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Two channel PCM and sound
« on: April 30, 2014, 10:23:48 am »

I'm sending lossless two channel PCM to my receiver.  I'm limited to two channel because I'm using optical out.  My music is flac.  I don't care about soundtracks on DVDs.

Settings:  ASIO  2 channels  JRSS Mixing  Output Encoding - None

Is it worth moving to HDMI from optical or does my receiver decode the two channel PCM as it would multiple channels.

Very confusing! 
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csimon

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Re: Two channel PCM and sound
« Reply #1 on: May 01, 2014, 04:53:22 am »

I'm not exactly sure what you are asking - your receiver will decode 2 channels as 2 channels and multiple channels as multiple channels.

Some people say HDMI is better for audio than SPDIF, other say the opposite.  HDMI can carry uncompressed multi-channel audio but for ordinary 2-channel music there is probably little difference.

If you send PCM stereo to your receiver, whether via SPDIF or HDMI, you can probably put the receiver into a pseudo-surround mode if you want (such as Pro-Logic) or allow it to process stereo only.
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thane108

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Re: Two channel PCM and sound
« Reply #2 on: May 01, 2014, 09:26:57 am »

Thanks for the help - I'm in the early stages of a learning curve trying to move from mp3 to flac and understand the settings to get the most out of flac format.

If I understand you correctly, most if not all of my music that is ripped from CDs to flac using JRiver are two channel anyway so it won't matter if I am going across optical to my receiver.

I also record over the air TV with JRiver - I suspect that the audio track is multiple channel for those over the air recording.  If I understand your correctly that is when switcing form optical to HDMI might improve sound somewhat if I were going across from the PC to receiver using HDMI.

Am I getting it yet?  If not, please feel free to correct me.  I would like to get the concepts down.

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csimon

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Re: Two channel PCM and sound
« Reply #3 on: May 01, 2014, 09:34:52 am »

I certainly don't think there will be any difference between SPDIF and HDMI for 2-channel uncompressed audio, others may feel free to argue!

I've no experience with recording TV with MC however if you're recording a multi-channel broadcast then it is highly likely to be a compressed form anyway, i.e. Dolby Digital 5.1 most likely, therefore SPDIF will reproduce this just as well as HDMI. You might like to apply decoding and further processing within MC first and then pump it out as uncompressed multichannel audio, in which case you'll have to use HDMI. However, I very much doubt whether you'd hear any difference whatsoever by just uncompressing the audio and sending it via HDMI. Remember that Dolby Digital 5.1 is what is provided on DVDs and is used in cinemas, it's not exactly a low-quality signal!
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thane108

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Re: Two channel PCM and sound
« Reply #4 on: May 01, 2014, 10:44:12 am »

OK - thanks - I think I'm getting it.

One last question - when I rip a CD to using JRiver is that always 2 channel?
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csimon

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Re: Two channel PCM and sound
« Reply #5 on: May 01, 2014, 02:06:26 pm »

Standard CDs are recorded in the "Red Book" standard which specifies 2-channel PCM, 16-bit, 44,1KHz (http://en.wikipedia.org/wiki/Compact_Disc_Digital_Audio) so yes, CD rips are always 2-channel.
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thane108

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Re: Two channel PCM and sound
« Reply #6 on: May 01, 2014, 04:15:02 pm »

Thanks - that gets it for me.

I experimented today with the HDMI connection.  Over-the-air recorded television in TS format does come across as Dolby Digital with multiple channels when I have the HDMI conveying both video and audio to the receiver.  It comes across as PCM when I'm on optical.

So - just like you said - TV sounds a little better on HDMI while my flac CDs sound the same whether I use optical of HDMI.

I can't get my little analog speakers on my computer to work while I have the computer outputting in HDMI so I guess I'll stick with optical until I find a work-around.

Thanks for helping me down the road to understanding the concepts!
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photovol777

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Re: Two channel PCM and sound
« Reply #7 on: May 07, 2014, 02:07:44 pm »

I'm not exactly sure what you are asking - your receiver will decode 2 channels as 2 channels and multiple channels as multiple channels.

Some people say HDMI is better for audio than SPDIF, other say the opposite.  HDMI can carry uncompressed multi-channel audio but for ordinary 2-channel music there is probably little difference.

If you send PCM stereo to your receiver, whether via SPDIF or HDMI, you can probably put the receiver into a pseudo-surround mode if you want (such as Pro-Logic) or allow it to process stereo only.
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thane108

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Re: Two channel PCM and sound
« Reply #8 on: May 07, 2014, 03:12:58 pm »

Maybe it's my imagination but I do hear a difference with HDMI when I play multiple channel sources.

I'm experimenting with two channel and multiple channel HD audio that I've downloaded.  I'm using bitstream and I unchecked Output Format so that the files aren't down sampled.  I then set my receiver to "pure" - and the sound is impressive.  With over-the-air recorded TV (in TS format) the sound is much improved - the music in Cosmos, for example, fills the room with my surround sound system.

I do understand (now . . .) that CDs that ripped to flac files are only two channel and that optical handles that just as well as HDMI.  Optical must adjust the sources with multiple channel and/or higher sample rates.  That's where HDMI makes a difference.

Not pretending to expertise here - this is all from playing with my system over the past week and trolling the various forums.

Still learning!
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