Hello,
The srtpenc plugin is part of the gstreamer1.0-plugins-bad package, but sometimes not all elements within a package are built by default due to missing dependencies or configuration options.
To resolve this issue, you need to ensure that the libsrtp development package is installed as it's a dependency for building the srtpenc element. You can add this to your Yocto build by modifying your local.conf file or creating a custom recipe to include libsrtp2-dev.
For your i.MX8MP board running 5.15 kirkstone, add the following to your local.conf:
```
IMAGE_INSTALL:append = " libsrtp2-dev"
PACKAGECONFIG:append:pn-gstreamer1.0-plugins-bad = " srtp"
```
Then rebuild the gstreamer1.0-plugins-bad package:
```
bitbake -c cleansstate gstreamer1.0-plugins-bad
bitbake gstreamer1.0-plugins-bad
```
After rebuilding your image and deploying it to your board, the srtpenc element should be available for your GStreamer pipelines.
You can verify the element's availability by running:
```
gst-inspect-1.0 srtpenc
```
Regards
