Optical Ootput - Compressed?

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coacharnold
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Optical Ootput - Compressed?

Post by coacharnold » Mon Sep 02, 2013 4:59 pm

Hi Folks .... quick question

If I am using the optical output on xbox A/V plug..... Is the digital S/PDIF signal compressed? Or is it just a nice clean PCM signal?

I'm using an outboard DAC now and the whole system sounds much better, but I've been wondering if what I'm getting off the optical output is under some compression.

Tim

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Re: Optical Ootput - Compressed?

Post by BuZz » Mon Sep 02, 2013 5:31 pm

only compressed in that if the data being sent down is compressed. as far as I know data is passed directly though, with a few exceptions that for example the ffmpeg passthrough code wraps AAC into ADTS frames. but basically there is no additional compression added.

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Re: Optical Ootput - Compressed?

Post by coacharnold » Mon Sep 02, 2013 10:50 pm

BuZz wrote:only compressed in that if the data being sent down is compressed.

as far as I know data is passed directly though, with a few exceptions that for example the ffmpeg passthrough code wraps AAC into ADTS frames.

but basically there is no additional compression added.

SO is it compressed or not???

EX: - A FLAC file coming across my network into the XBOX > into the optical output > into a stand alone DAC ......... is the FLAC getting un-compressed in the XBOX and then into compressed pcm before being passed into the optical output?

T

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Re: Optical Ootput - Compressed?

Post by BuZz » Tue Sep 03, 2013 12:49 am

yeh sorry, so flac, mp3 etc will be decoded by the xbox and the raw PCM stream sent over the spdif. our decoding libraries for mp3/flac are of a high quality though. very few amps supports mpX passthrough and I had some test code before, but no-one had an amp that supported it. I doubt there would be any quality increase though anyway, just less CPU utilisation.

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Re: Optical Ootput - Compressed?

Post by coacharnold » Tue Sep 03, 2013 12:19 pm

Cool Buzz ....

Thank you ...thats sort of what I thought ... you just confirmed it ..

I'm working with a small company trying to develop a small media box out of devices manufactured now in Asia. I can't get anything to compete with my old war horse XBOX....

T

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Re: Optical Ootput - Compressed?

Post by Redneck9 » Fri Oct 11, 2013 1:22 am

In 3.1build there are more receiver codec decoding rules:

mpeg2,mpeg3 and mpeg4 (in addition to dolby,dts and aac)

Can I add or modify a line in 3.3 so my receiver will decode them?

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Re: Optical Ootput - Compressed?

Post by BuZz » Fri Oct 11, 2013 1:32 am

Redneck9 wrote:In 3.1build there are more receiver codec decoding rules:

mpeg2,mpeg3 and mpeg4 (in addition to dolby,dts and aac)

Can I add or modify a line in 3.3 so my receiver will decode them?
there were settings for mp1/2/3 (audio) and they never worked - or I was never able to test, as I did not have an av receiver with support. settings are removed, and are not needed anyway.

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Re: Optical Ootput - Compressed?

Post by Redneck9 » Fri Oct 11, 2013 1:37 am

alright.

I'll test the 3.1 build then post my findings after my parcel arrives, just for the sake of knowing/future reference I guess.

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Re: Optical Ootput - Compressed?

Post by BuZz » Fri Oct 11, 2013 1:48 am

What av receiver do you have?

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Re: Optical Ootput - Compressed?

Post by Redneck9 » Fri Oct 11, 2013 4:02 am

Its a TV (I have a component/spdif to HDMI converter)

"Samsung series 5 LED"


TV uses FFmpeg v.0.6.90 opensource codecs.

TV Has a DTS chipset that decodes standard DTS
TV Has a Dolby Chipset that decodes Dolby Digital (ac3) and Dolby Digital Plus (eac3)





*BTW since spdif can support bitrates up to 6144 Kbit/s. Can you update XBMC to support DDPlus and/or DTS-hd-hr?

http://en.wikipedia.org/wiki/Spdif

Though I was reading and IDKFS, that there isn't a standalone ffmpeg dts-hd-hr demuxer. There is only a ffmpeg dts-hd-master demuxer that supports both codecs.

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Re: Optical Ootput - Compressed?

Post by BuZz » Fri Oct 11, 2013 4:17 am

Redneck9 wrote:Its a TV (I have a component/spdif to HDMI converter)

"Samsung series 5 LED"

*BTW since spdif can support bitrates up to 6144 Kbit/s. Can you update XBMC to support DDPlus and/or DTS-hd-hr?
that doesn't mean it would handle a raw mp3 data stream though. feel free to try it out though as you like.

No plans to look at hd audio formats etc. I didn't think spdif has enough bandwidth for dts-hd, but in any case it isn't going to happen (at least not from me). This is an xbox 1 - if you care about such things, you should go and get a modern htpc.

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Re: Optical Ootput - Compressed?

Post by Redneck9 » Tue Oct 15, 2013 10:10 pm

3.1 and 3.3 will send 48khz aac, dts, and ac3 over spdif using both DVDPlayer and MPlayer (3.1 mp3 could not be decoded by my TV or sony AVR)

44.1khz aac, and ac3 will not output over spdif. It sends encodes as 48khz LCPM.

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