HDMI Audio Setting

Document created by Daiane Angolini Employee on Nov 6, 2012Last modified by Jodi Paul on May 20, 2013
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1. Set up HDMI

Set up your kernel to use HDMI adding the following code to bootargs on u-boot:

 

video=mxcfb0:dev=hdmi,1920x1080M@60,if=RGB24

 

2. Test raw audio

 

In order to test only raw audio, use the following command:

 

aplay -D hw:1,0 Kaleidoscope.wav

 

 

3. Make HDMI audio the default output

 

In order to configure audio output over HDMI, please, replace content of file ~/.asoundrc to the following one

pcm.dmix_48000{

     type dmix

     ipc_key 5678293

     ipc_key_add_uid yes

     slave{

          pcm "hw:1,0"

          period_time 0

          period_size 2048

          buffer_size 24576

          format S16_LE

          rate 48000

     }

}

 

pcm.!dsnoop_44100{

     type dsnoop

     ipc_key 5778293

     ipc_key_add_uid yes

     slave{

          pcm "hw:0,0"

          period_time 0

          period_size 2048

          buffer_size 24576

          format S16_LE

          rate 44100

     }

}

 

pcm.!dsnoop_48000{

     type dsnoop

     ipc_key 5778293

     ipc_key_add_uid yes

     slave{

          pcm "hw:1,0"

          period_time 0

          period_size 2048

          buffer_size 24576

          format S16_LE

          rate 48000

     }

}

 

pcm.asymed{

     type asym

     playback.pcm "dmix_48000"

     capture.pcm "dsnoop_44100"

}

 

pcm.dsp0{

     type plug

     slave.pcm "asymed"

}

 

pcm.!default{

     type plug

     route_policy "average"

     slave.pcm "asymed"

}

 

ctl.mixer0{

     type hw

     card 0

}


This will configure alsa to use sound card hw:1,0. Please, pay attention to use the proper audio card name for your device.

 

In order to see available sound cards on board:

 

root@imx53qsb:~# aplay -l

**** List of PLAYBACK Hardware Devices ****

card 0: imx3stack [imx-3stack], device 0: SGTL5000 SGTL5000-0 []

  Subdevices: 1/1

  Subdevice #0: subdevice #0

card 1: imx3stackspdif [imx-3stack-spdif], device 0: IMX SPDIF mxc spdif-0 []

  Subdevices: 1/1

  Subdevice #0: subdevice #0

For detail on how to create asound.conf, please see alsa-lib Configuration Introduction.

 

4. Encoded audio

 

For encoded (i.e. AC3, DTS) audio, you can use, for example, ac3dec, an utility provided by alsa-tools with the following command line:

 

ac3dec -D hw:1,0 -C test.ac3

 

This would work for both HDMI audio and SPDIF audio. Double check your hardware and/or schematic in order to know which one to use.

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