Usage of v4l2_wrapper

[philolt]

Hi,
How can I use the compiled libyami_v4l2.so to expose the hardware codecs via v4l2? The only device which is visible is the integrated Webcam of my intel notebook. I searched the whole repo but didn't find a hint how to setup.
thanks and best regards

[xuguangxin]

Hi @PipOlt ,
thanks for interested on this.
all v4l2 functions exposed by https://github.com/intel/libyami/blob/apache/interface/v4l2_wrapper.h
you can refer to https://github.com/intel/libyami-utils/blob/master/tests/v4l2decode.cpp
for api usage.
here is some high level introduction. https://github.com/intel/libyami/wiki/V4L2-Codec. You can read it with code, but it's little old, not all information is accurate.

[philolt]

Hi @xuguangxin,
Thank you for your fast response. I thought, the v4l2-wrapper acts as a v4l2-device like a capture card. I found all of the documents you posted earlier. But I don't understand how to load the library in a normal linux environment. I expected an exposed device like /dev/video$X for the v4l2 codec. But therefore I need something like a kernel Module. Can you explain how this is working especially in context of video acceleration under chromium?
best regards!

[xuguangxin]

@PipOlt , No, it's for decoder and encoder. not for capture.
here is the example how to use it https://github.com/intel/libyami-utils/blob/master/tests/V4L2Device.cpp#L219
chrome has similar class https://github.com/chromium/chromium/blob/master/media/gpu/v4l2/v4l2_device.h#L393.
If you write a chrome wrapper and hook it up here https://github.com/chromium/chromium/blob/master/media/gpu/v4l2/v4l2_device.cc#L984. you may plugin it to chrome.

thanks

[philolt]

@xuguangxin Ok, thank you for the information. I thought it would be possible to load the codec as a device of v4l2 like this https://github.com/torvalds/linux/blob/master/drivers/media/platform/vicodec/vicodec-core.c. It can be loaded as kernel module and then there is a entrypoint at /dev/video* for the codec.
thanks!

[xuguangxin]

no, it's a simulation for v4l2 in user space. nothing related to the kernel module