Difference between revisions of "Category:HOWTO"

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== To send sound to both DVI and HDMI via ALSA ==
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Documents in this category are HOWTO documents explaining a specific scenario or task. You'll often find that they're more specific than you need, or that they pertain to a slightly different environment than you have, but you can often generalize about what they say to help you, anyway.
eg. to TV and Amplifier simultaneously you can use an .asoundrc file in your home directory.
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Firstly a note or two -
 
# Sound CAN be sent over DVI, if you sound card supports it. Preferably use a DVI to HDMI connector / cobale (often cheaper than an HDMI to HDMI cable)
 
# Your sound device (presumably a graphics card with built in sound eg. NVidia GT430 as used here) needs to treat DVI and HDMI connectors similarly
 
# The sound device (graphics card) needs to support sound
 
  
Secondly, Pulse is probably easier if that is what you use, but this is useful for those of us using ALSA
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[[Category:Knowledge Base]]
 
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===The asoundrc file===
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<pre>
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# .asoundrc
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# Add to your home directory
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# works with NVidia GT430 ... once the video card itself is set to work correctly
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#
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# Default ALSA to send to both DVI and HDMI
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pcm.!default {
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    type plug
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    slave {
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        # The following line actually does the work
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        pcm "hdmi_dvi_both"
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    }
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}
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# DVI connection on GT430
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pcm.!hdmi3 {
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    type hw
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    card 0
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    device 3
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    channels 2
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}
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# Doesn't seem to be necessary, just for completeness
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ctl.!hdmi3 {
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    type hw
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    card 0
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    device 3
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    channels 2
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}
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pcm.!hdmi7 {
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    type hw
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    card 0
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    device 7
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    channels 2
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}
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pcm.!hdmi8 {
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    type hw
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    card 0
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    device 8
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    channels 2
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}
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# HDMI Connection on GT430
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pcm.!hdmi9 {
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    type hw
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    card 0
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    device 9
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    channels 2
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}
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# Doesn't seem to be necessary, just for completeness
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ctl.!hdmi9 {
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    type hw
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    card 0
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    device 9
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    channels 2
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}
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pcm.multi_dig {
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    type multi
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    # Define DVI slave
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    slaves.a {
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        pcm "hdmi3"
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        # In this version, only pass 2 channels (like SPDIF)
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        channels 2
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    }
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    # Define HDMI slave
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    slaves.b {
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        pcm "hdmi9"
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        # In this version, only pass 2 channels (like SPDIF)
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        channels 2
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    }
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    # Bind the 2 DVI channels to a name ie "a"
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    bindings.0.slave a
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    bindings.0.channel 0
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    bindings.1.slave a
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    bindings.1.channel 1
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    # Bind the 2 HDMI channels to a name ie "b"
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    bindings.2.slave b
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    bindings.2.channel 0
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    bindings.3.slave b
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    bindings.3.channel 1
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}
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# Define the routing which actually send s the signal to both DVI and HDMI
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pcm.hdmi_dvi_both {
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    type route
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    slave {
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        pcm "multi_dig"
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        # The channels definition is critical to define the total number of channels out (2 sets of 2)
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        channels 4
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    }
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    # The first dot after "ttable" defines the channel out
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    # The second dot defines the channel as bound above in the "multi-dig" definition
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    # Define 4 channels out in total, 2 each for DVI and HDMI
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    ttable.0.0 1
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    ttable.1.1 1
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    ttable.0.2 1
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    ttable.1.3 1
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}
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# You may have to mess around with your TV and amp depending on what they support
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# My curent setup is MythTv v 0.23
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# my amp supports Dolby, DTS and AC3
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# my TV support DTS and AC# ... but NOT Dolby (just get nasty "noise" if "dolby" selected in MythTv)
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# I sent HDMI to TV because of default colour space etc
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# and DVI to amp cause its not sensitive to colour etc. (just used for sound)
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# BUT need to tell NVidia Config to send video to both (default is DVI only)
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</pre>
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Paste the above file into your home directory as ".asoundrc"
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=== MythTv Setup ===
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Go to MythTv Setup / General / Audio System and set the "Audio output device" to ALSA:default or ALSA:hdmi_dvi_both
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=== Other Notes ===
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Depending on your TV and Amp you may also need to change the settings for 5.1 sound. Your devices may or may not support
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# AC3 (nothing else selected)
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# Dolby
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# DTS
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In my case,
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# TV supports AC3 and DTS but NOT Dolby
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# Amp supports all the above (but not 7.1 bitstream)
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Now I can use either TV sound or Amp sound or both
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[[Category:HOWTO]]
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Latest revision as of 12:41, 7 March 2011

Documents in this category are HOWTO documents explaining a specific scenario or task. You'll often find that they're more specific than you need, or that they pertain to a slightly different environment than you have, but you can often generalize about what they say to help you, anyway.

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