How do you build the Pion mediadevices webrtc example?

Issue

I was checking out Pion Mediadevices and trying to cross-compile the webrtc example for a rasperry pi zero from my windows computer. When I try to build the example though, I get these errors from Windows command prompt:

    # github.com/pion/mediadevices/pkg/codec/mmal
..\..\pkg\codec\mmal\params.go:30:9: undefined: newEncoder
# github.com/pion/mediadevices/pkg/driver/microphone
..\..\pkg\driver\microphone\microphone.go:27:10: undefined: malgo.AllocatedContext
..\..\pkg\driver\microphone\microphone.go:34:2: undefined: malgo.DeviceInfo
..\..\pkg\driver\microphone\microphone.go:40:13: undefined: malgo.InitContext
..\..\pkg\driver\microphone\microphone.go:40:36: undefined: malgo.ContextConfig
..\..\pkg\driver\microphone\microphone.go:78:25: undefined: malgo.DeviceInfo

Also because the program is for the pi zero I edited the import section to have "github.com/pion/mediadevices/pkg/codec/mmal" and commented out the x264 import.
What is the correct way to build this example?

Edit: Upon further investigation, I found that the error message above:

 ..\..\pkg\codec\mmal\params.go:30:9: undefined: newEncoder

correlates to a call to the function newEncoder which is declared in a seperate go file, mmal.go, in the same folder as params.go. Both of these files have package mmal at the top before their imports and the folder they’re contained in is also called mmal. Is there any problems there causing the function to not be viewable to params.go?

Solution

mediadevices currently uses cgo to give us access to camera/microphone and codecs. Cross-compiling in cgo is possible but you would very likely need to cross-compile mmal codec as a static library yourself, but this requires access to the source code.

Unfortunately, mmal is not an open-source library. Therefore, the only option left is to compile the library on the raspberry pi since mmal should be installed on your system already.

Note: I’m the mediadevices author 😃.

Answered By – Lukas Herman

Answer Checked By – Marie Seifert (GoLangFix Admin)

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