GSOC 2017 EGLImage

This week we looked into how to add EGLImage support in the new component and other small work.

Adding EGLImage support

An EGLImage is simply a texture whose content can be updated without having to copy the contents to system memory. The format of an EGLImage is opaque to the EGL’s client by design, so any memory allocated through OMX_UseEGLImage macro are not accessible directly by the IL client.

Right now RPI is the only platform where OMX_UseEGLImage code path in gst-omx works at the moment. It is hard to maintain because developing directly on board is harder. After adding this support this code will be able to run on desktop too which will be much easier than developing on the board. The decoder will decode directly in the gpu memory. Without OMX_UseEGLImage, the gst pipeline copies buffers from gpu memory to system memory when decoding and copy back from system memory to gpu memory when rendering with OpenGL, which is quite inefficient.

Components should inspect the EGLImage and determine if the EGLImage is
compatible with the port configuration. A validation hook is registered to check the validity of the returned EGLImage. To get the EGLImage the decoder will have to check OMX_BUFFERHEADERTYPE->pBuffer nullity. In case it is NULL it means it has an EGLImage underneath. Using tiz_krn_claim_eglimage that EGLImage can be retrieved. What still isn’t clear is how to write to the EGLImage in st/omx_tizonia/omxh264dec. For now we are trying to retrieve the mesa pipe screen pointer from the egl_display (pNativeWindow).

Code cleanup

The 42 commits on the gsoc-dev branch were cleaned up and reduced down to 4 commits on the gsoc branch.

GPU Upgrade

Also this week I replaced my older NVIDIA card with AMD RX 460. No blockiness during decoding and the ability to use (older st/omx) and develop the encoder component (new st/omx_tizonia) are some of the benefits from this switch.


Next week’s goals are to find a way to write output to EGLImage and to start adding new components like omxh264enc.


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