audio devices and system?

Morgan

New Member
Hello Folks
I've been sniffing around but can't seem to find much info on how the audio works. ALSA doens't seem to be installed so I guess the audio is some custom setup?
What I'm really trying to work out is:
Can I get audio out of the USB port?
The only module loaded listed by lsmod seems to be bcmdriver... and it shows used by 2 others - but no other modules listed...
So, I guess that's not the end of the story - does anyone know how sound works and whether it can be directed to another device, a device on the usb port?
Thanks
Morgan.
 

Black Hole

May contain traces of nut
You've posted in the HDR-FOX section of the forum rather than the section dedicated to customisation of the HDR-FOX... but that's OK, the thread will be moved.

Can I get audio out of the USB port?
The heavy lifting of stream decoding and output is all handled by hardware modules inside the Broadcom system-on-chip (SoC). These are not the software pipes you might find on a standard PC OS implementation. So no, the data from the tuner or a recorded file is directed to hardware decoders which then output directly to the HDMI, SCART, RCA, and TOSLink ports.
 
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Morgan

New Member
Many thanks for the re-direction and answer BH - I guess this system on chip is called a nexus chip as there's so many nexus_* hardware thingys under the /dev directory? I figured something like that would be the answer.
 

/df

Active Member
Nexus is the library provided by Broadcom for developers to use the multimedia facilities of their SoC products; in this case the SoC is BCM7405, for which some information is available on the net.

As far as anyone knows the only way to get sound into the Linux domain is to read it from media files, but then there's no way to get it out, except to save a file and play it back. Conceivably you could build a custom kernel to support USB audio. Then you could route the system's audio out (digital, ideally, or parasitise the analogue L+R) into the input of a USB audio gadget and acquire the audio into some Linux program and/or play audio through the gadget's output.
 
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Morgan

New Member
Hi, thanks BH. I guess this is what's called TiVoisation... I'm just banging my head against it about 18 years after everyone else :eek:) F Linus. Sorry, lets not wake that old dog.

What was I trying to achieve:
My monitor (panny plasma) produces some rather nasty noise when connected to ground, which it is by a 3 pin earthed plug. It's not 50Hz hum, but doesn't exist when I disconnect it from ground. Anyway, that hum wizzes around the shields of all the audio kit to produce said nasty sound. Originally, I was going to isolate the hum at the Humax by using TOSLink to the audio system - but, the audio system has coax spdif. Then I remembered, I have a very nice little usb-spdif converter (Peachtree X1) which isolates and puts out both optical & coax spdif from a usb input. And, I thought sitting between the Humax and my audio system would be a very nice job for it to do - if it could, but it can't.

Thanks again.
Morgan.
 
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Morgan

New Member
PS, so what does /dev/nexus_audio do - is it audio input to this monolithic chunk of silicon stuff or is it just a control interface and all the audio stays inside and never comes out?
Oh, I see where that's covered in the second to last heading in that thread - so, it's a control IF which no one except for Broadcom and Humax know anything about... Thanks Linus.
 
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