How to route audio to S/PDIF ?

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How to route audio to S/PDIF ?

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andreygelman
Contributor III

I run JellyBean 4.3 on i.MX6-based device ...

While my kernel supports S/PDIF all right (tested with Debian user space), I cannot figure out how to route sound to spdif in Android user space.

Any advice will be highly appreciated !

-- Andrey

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andreygelman
Contributor III

For the sake of all the lost souls out there, the solution that I have eventually figured out ...

[1]

Look at hardware/imx/alsa/config_spdif.h

static struct audio_card  spdif_card = {

     .name = "imx-spdif",

     .driver_name = "imx-spdif",

-    .supported_out_devices   = 0,

+    .supported_out_devices   = AUDIO_DEVICE_OUT_AUX_DIGITAL,

     .supported_in_devices    = AUDIO_DEVICE_IN_AUX_DIGITAL,

S/PDIF must be registered as output device.

However there is one problem - AUDIO_DEVICE_OUT_AUX_DIGITAL is actually HDMI audio output.

Q: So which audio sink will be selected automatically ?

A: The one that was registered first by the kernel, i.e. the first kernel module that was loaded at boot time. Refer to tinyalsa_hal.c:get_card_for_device() if you don't believe.

[2]

Here we suggest a solution to the HDMI/SPDIF competition, so that HDMI and S/PDIF could co-exist side by side.

Let's assign to spdif_card.supported_out_devices a sink that is not used in our device - in my device it would be AUDIO_DEVICE_OUT_WIRED_HEADPHONE, as there is no headphones.

So make sure no other audio sink in use registers itself as AUDIO_DEVICE_OUT_WIRED_HEADPHONE ...

hardware/imx/alsa/config_wm8731.h

.supported_out_devices = (

     AUDIO_DEVICE_OUT_EARPIECE |

     AUDIO_DEVICE_OUT_SPEAKER |

     AUDIO_DEVICE_OUT_WIRED_HEADSET |

-    AUDIO_DEVICE_OUT_WIRED_HEADPHONE |

hardware/imx/alsa/config_spdif.h

static struct audio_card  spdif_card = {

     .name = "imx-spdif",

     .driver_name = "imx-spdif",

-    .supported_out_devices   = AUDIO_DEVICE_OUT_AUX_DIGITAL,

+    .supported_out_devices   = AUDIO_DEVICE_OUT_WIRED_HEADPHONE,

     .supported_in_devices    = AUDIO_DEVICE_IN_AUX_DIGITAL,

Now select "Wired headphones" to play S/PDIF.

[3]

Q: How to select "Wired headphones" as Android-wide audio sink ?

A: There are applications in Google Play Store. One that I have tested with is AudioAbout.

View solution in original post

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andreygelman
Contributor III

For the sake of all the lost souls out there, the solution that I have eventually figured out ...

[1]

Look at hardware/imx/alsa/config_spdif.h

static struct audio_card  spdif_card = {

     .name = "imx-spdif",

     .driver_name = "imx-spdif",

-    .supported_out_devices   = 0,

+    .supported_out_devices   = AUDIO_DEVICE_OUT_AUX_DIGITAL,

     .supported_in_devices    = AUDIO_DEVICE_IN_AUX_DIGITAL,

S/PDIF must be registered as output device.

However there is one problem - AUDIO_DEVICE_OUT_AUX_DIGITAL is actually HDMI audio output.

Q: So which audio sink will be selected automatically ?

A: The one that was registered first by the kernel, i.e. the first kernel module that was loaded at boot time. Refer to tinyalsa_hal.c:get_card_for_device() if you don't believe.

[2]

Here we suggest a solution to the HDMI/SPDIF competition, so that HDMI and S/PDIF could co-exist side by side.

Let's assign to spdif_card.supported_out_devices a sink that is not used in our device - in my device it would be AUDIO_DEVICE_OUT_WIRED_HEADPHONE, as there is no headphones.

So make sure no other audio sink in use registers itself as AUDIO_DEVICE_OUT_WIRED_HEADPHONE ...

hardware/imx/alsa/config_wm8731.h

.supported_out_devices = (

     AUDIO_DEVICE_OUT_EARPIECE |

     AUDIO_DEVICE_OUT_SPEAKER |

     AUDIO_DEVICE_OUT_WIRED_HEADSET |

-    AUDIO_DEVICE_OUT_WIRED_HEADPHONE |

hardware/imx/alsa/config_spdif.h

static struct audio_card  spdif_card = {

     .name = "imx-spdif",

     .driver_name = "imx-spdif",

-    .supported_out_devices   = AUDIO_DEVICE_OUT_AUX_DIGITAL,

+    .supported_out_devices   = AUDIO_DEVICE_OUT_WIRED_HEADPHONE,

     .supported_in_devices    = AUDIO_DEVICE_IN_AUX_DIGITAL,

Now select "Wired headphones" to play S/PDIF.

[3]

Q: How to select "Wired headphones" as Android-wide audio sink ?

A: There are applications in Google Play Store. One that I have tested with is AudioAbout.

View solution in original post

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igorpadykov
NXP TechSupport
NXP TechSupport

Hi Andrey

I think suggestions from link below may be useful

set correct device & card number for your SPDIF device.

tinyplay test.wav -D 1 -d 0

to see the SPDIF device in kernel log like this.

   ALSA device list:

   #0: sgtl5000-audio

   #1: imx-spdif

   #2: imx-hdmi-soc

[Android] How to support SPDIF input feature?

Best regards

igor