USB audio through external VGA->HDMI adapter

Libretro Lakka
#1

Hello,

I am new to Lakka (and quite like it). However, I have been using linux as my primary OS for about fifteen years now, and I’m pretty comfortable with needing to tweak things.

I have installed a recent Lakka nightly (21205) on an old Dell e1505 laptop (64-bit 2-core Intel T7400 cpu, 2GB ram, ATI X1400 gpu), and many things are working great. The system even dual-boots with Fedora.

Since this is a circa 2008-ish laptop, it comes from before the era when having an HDMI port was common. I am using an external VGA->HDMI adapter that receives the audio portion of the signal from USB. (http://amzn.com/B014V0VYQS). Lakka detected the external HDMI monitor (a regular LCD TV) without a problem, but needed some coaxing to properly use the USB audio.

Using information found here (https://pirraste.wordpress.com/2014/02/28/retroarch-alsa-audio-over-hdmi-working/), I was able to edit /storage/.config/retroarch/retroarch.cfg with the proper “audio_device” setting.

In short:

[ul] ssh into your Lakka system list your audio devices by calling: $> aplay -l determine which one looks like your USB audio device [/ul]

[ul] This is what appears on my Lakka system [/ul]

**** List of PLAYBACK Hardware Devices ****
card 0: Intel [HDA Intel], device 0: STAC9200 Analog [STAC9200 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: Intel [HDA Intel], device 1: STAC9200 Digital [STAC9200 Digital]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: Set [C-Media USB Headphone Set], device 0: USB Audio [USB Audio]
  Subdevices: 0/1
  Subdevice #0: subdevice #0

[ul] The last line is my USB audio device - Card 1, Device 0 So in retroarch.cfg, I need [LIST] audio_device = “hw:1,0” [/ul] [/LIST]

#2

I discovered a side effect that I thought I should share.

When the usb audio adapter is physically unplugged, Lakka failed to boot to the RetroArch gui. System logs show a number of segfaults similar to this…


[   10.195373] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[   10.258393] EXT4-fs (sda2): mounted filesystem with ordered data mode. Opts: (null)
[   12.451259] retroarch[318]: segfault at 12 ip 00000000004699d0 sp 00007ffcd17d4188 error 4 in retroarch[400000+18b000]
[   13.336887] b44 ssb1:0 eth0: Link is up at 100 Mbps, full duplex
[   13.336897] b44 ssb1:0 eth0: Flow control is off for TX and off for RX
[   13.337007] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[   15.987275] retroarch[496]: segfault at 0 ip           (null) sp 00007fad6ade8d88 error 14 in retroarch[400000+18b000]
[   18.987268] retroarch[501]: segfault at 0 ip           (null) sp 00007f0d7134bd88 error 14 in retroarch[400000+18b000]
[   21.987268] retroarch[506]: segfault at 0 ip           (null) sp 00007f3efe7a5d88 error 14 in retroarch[400000+18b000]
[   24.987270] retroarch[511]: segfault at 0 ip           (null) sp 00007fa72a123d88 error 14 in retroarch[400000+18b000]

It seems to happen right around the time the wired network interface is brought up (not sure how they’re related, if it’s just a coincidence, or it’s some other artifact of the boot process).

Regardless, connecting via ssh, setting audio_device = “” in retroarch.cfg, and rebooting allowed the boot process to finish normally. Since audio_device is the only thing I changed, I imagine the segfault and the unplugged usb audio adapter are related.

I’m putting this here in case anyone else encounters this problem and is looking for a solution.

#3

Hi usury, and welcome :slight_smile:

It’s very strange that this segfault happens when network shows up… It looks pretty unrelated. But who knows? Have you tried to reproduce it many times?

#4

Perhaps not many times, but I did have two successive reboots (with the USB audio device disconnected and an inaccessible audio device configured in “audio_device”) that exhibited the same behavior (lack of UI) and had segfaults in the log. After resetting “audio_device” I have had three successive reboots where all worked as intended. I can try to get it to break again when I ultimately futz with it tomorrow.

#5

Turns out, about every third reboot I see the segfaults. But the system and the network adapters apparently work fine (wired, wifi, and both simultaneously). The GUI loads and works. I can ssh into the machine.

i don’t think the originally observed “audio_device” setting has anything to do with the segfaults. Maybe this particular laptop has flakey network hardware.

#6

Hello, I also have an old laptop with only a vga output. I want to connect it to my tv with an external vga->hdmi adapter but the screen stays black. How did you get it to work?

Greetings,

Hannes

#7

@Elkevro : Please provide the output of available output. Thank you.

#8

Hello,

I don’t find what I need. I have an old laptop with only 1 VGA output that I want to connect to my tv with an external vga->hdmi adapter. I’m a linux noob so forgive me if this is a stupid question.

Kind regards,

Hannes