How compile OPUS

[Michal]

Hello,

I am working on ble/audio application on nrf52832. I would like to know how to compile OPUS codec (used in smart remote) so I can use it on arm cortex. For now I compiled it with simplest path (./configure; make; make install) but when I try to link it to my application is says 

libopus.a: error adding symbols: File format not recognized

Any help is welcomed.

Michal

[Stian Røed Hafskjold]

Hi, where did you find the OPUS source? Maybe you compiled the lib file for GCC and tried to link it in your Keil project?

[Michal]

I am not using Keil, I use gcc only. 

I downloaded sources from opus site - http://www.opus-codec.org/. My feeling is that I somehow need to specify target (arm cortex). From logs I see it using my gcc compiler for windows instead of arm-none-eabi-gcc compiler. Is there a tutorial how to confiugre opus regarding it was used in smart remote? Or maybe all needed sources are in smart remote code and I would only need to buy smart remote with access to its code? I am trying to get through configuration but no results for now.

I really would appriciate help, if we wont be able to run opus then we would need to add external IC for mp3 decoding. We would like to avoid this as it will raise production costs. I know opus is integrated within smart remote project so I hope you can help me.

[Stian Røed Hafskjold]

Ok, yes, you need to compile for the right target with the arm-none-eabi-gcc compiler. Not sure if opus provides any tutorial for how to compile their source for ARM. But  yes, the source code is in the Smart Remote package, so you can look at the Makefiles for the projects there and include the opus source in your project in a similar way.

You can download the FW here: http://www.nordicsemi.com/eng/Products/Bluetooth-low-energy/nRFready-Smart-Remote-3-for-nRF52-Series#Downloads  You do not need to buy the Smart Remote to download the FW.

[Michal]

Thank you Stian! I will check that and get back with results.

[Michal]

So I checked out sources of SR and took opus and integrated it into my project. It is already very much help but I would need to do some decoding with opus. I think it wont be a problem but maaybe there are examples on decoding from Nordic?

[Michal]

So I am still unable to do decoding but I have small success. I am able to run encode on pcm samples from sd card, save it to file on sd and then read it, decode it back to pcm. And when I play it with my dac it works. The problem is that when I take the .opus file from sd card and try to decode it on pc with opustools, the tool says it is not an opus file. So maybe that is also problem when I try to decode .opus file from taken from pc? Is it possible that files encoded on nrf are not compliant with opus format somehow? 

EDIT: So I took a look at opus specification and I can see that header is present in every .opus file. Does SR implements adding header to .opus file? 

[Stian Røed Hafskjold]

We can continue the discussion in this thread: https://devzone.nordicsemi.com/f/nordic-q-a/33414/opus-decoder