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Sound card for recording SPDIF optical ?
Xrcr9709
post Jan 20 2013, 13:51
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Hello,

Since it seems to me that SPDIF (optical) = numeric. I guess that any PC sound card with optical in will do exactly the same job ? Even the cheapest ones ? Or can some cards perfoms differently ? (Regarding quality etc.)


Thank you for information
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phofman
post Jan 20 2013, 23:17
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Yes but you have to make sure the card uses recovered clock from the incoming SPDIF stream as its master clock. It is no problem for the cards which specifically offer "external clock" switch. However, a simple USB card with SPDIF input like http://www.ebay.com/itm/External-USB-2-0-7...=item2320e5a362 which does not offer any external clock switch, only the input selector switch (the first control called "PCM Capture Source"):

CODE

pavel@eeepc:~$ amixer -c 1 contents
numid=14,iface=MIXER,name='PCM Capture Source'
; type=ENUMERATED,access=rw------,values=1,items=4
; Item #0 'Mic'
; Item #1 'Line'
; Item #2 'IEC958 In'
; Item #3 'Mixer'
: values=0
numid=12,iface=MIXER,name='PCM Capture Switch'
; type=BOOLEAN,access=rw------,values=1
: values=on
numid=13,iface=MIXER,name='PCM Capture Volume'
; type=INTEGER,access=rw---R--,values=2,min=0,max=6928,step=0
: values=5543,5543
| unk-4-0x00000000,0x00000452,
numid=3,iface=MIXER,name='Line Playback Switch'
; type=BOOLEAN,access=rw------,values=1
: values=off
numid=4,iface=MIXER,name='Line Playback Volume'
; type=INTEGER,access=rw---R--,values=2,min=0,max=8065,step=0
: values=6144,6144
| unk-4-0x00000000,0x000002ee,
numid=9,iface=MIXER,name='Line Capture Switch'
; type=BOOLEAN,access=rw------,values=1
: values=off
numid=10,iface=MIXER,name='Line Capture Volume'
; type=INTEGER,access=rw---R--,values=2,min=0,max=6928,step=0
: values=0,0
| unk-4-0x00000000,0x00000452,
numid=1,iface=MIXER,name='Mic Playback Switch'
; type=BOOLEAN,access=rw------,values=1
: values=off
numid=2,iface=MIXER,name='Mic Playback Volume'
; type=INTEGER,access=rw---R--,values=2,min=0,max=8065,step=0
: values=0,0
| unk-4-0x00000000,0x000002ee,
numid=7,iface=MIXER,name='Mic Capture Switch'
; type=BOOLEAN,access=rw------,values=1
: values=off
numid=8,iface=MIXER,name='Mic Capture Volume'
; type=INTEGER,access=rw---R--,values=2,min=0,max=6928,step=0
: values=0,0
| unk-4-0x00000000,0x00000452,
numid=11,iface=MIXER,name='IEC958 In Capture Switch'
; type=BOOLEAN,access=rw------,values=1
: values=on
numid=5,iface=MIXER,name='Speaker Playback Switch'
; type=BOOLEAN,access=rw------,values=1
: values=on
numid=6,iface=MIXER,name='Speaker Playback Volume'
; type=INTEGER,access=rw---R--,values=8,min=0,max=197,step=0
: values=158,158,158,158,158,158,158,158
| unk-4-0x00000000,0x00000000,


Will the CM106 chip http://www.steila.com/USB4IO/CMedia/CM106-...tasheet-1.3.pdf inside the soundcard switch its clock from its internal oscillator to the clock recovered by its internal SPDIF receiver when it is directed to switch input to the "IEC958 In" source? I don't know smile.gif

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Arnold B. Kruege...
post Jan 21 2013, 13:48
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QUOTE (phofman @ Jan 20 2013, 17:17) *
Yes but you have to make sure the card uses recovered clock from the incoming SPDIF stream as its master clock. It is no problem for the cards which specifically offer "external clock" switch. However, a simple USB card with SPDIF input like http://www.ebay.com/itm/External-USB-2-0-7...=item2320e5a362 which does not offer any external clock switch, only the input selector switch (the first control called "PCM Capture Source"):


The above seems to makes no sense. When receiving SP/DIF there is and can be no source of clocking information other than the input data stream. The clock that is used to decode the input data stream must be sample-aligned with the input data and therefore synchronized with it.

External clocking does not usually affect the reception of input SP/DIF data streams. External clocking geneally affects only the output data stream which may be clocked by an internal or external clock. Often there is an option for the output clock to be synchronized with the input data stream.

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