Support for Subtitle Functionality in GStreamer (MI-X) Plugins

Intel^® EMGD supports subtitle functionality with GStreamer (MI-X) Plugins; supported subtitle formats are .srt and .smi. The file is converted to a text subpicture by the GStreamer plugins module before it is delivered to the graphics driver for further processing. GStreamer uses VAAPI to interface with Intel^® EMGD for hardware video decoding and blending the text subpicture on a frame-by-frame basis. This feature is supported on both single and dual display modes.

The subtitle will be displayed on the framebuffer, so ensure you set the option “SubpictOnFb” (SubpictOnFb = 1) in xorg.conf to enable this feature.

Alpha Blending is used to blend the display plane with the overlay or sprite-C plane. In alpha blending mode, the display plane is blended to the overlay/sprite-C plane according to the alpha value. So you can get different transparency depending on the specific color in the display plane. This approach has better font appearance.

To enable subtitle with alpha blending capability, configure the xorg.conf with the following parameters:

• To enable “Sub picture on Framebuffer”

Option "ALL/1/General/SubpictOnFb" "1"

• To enable “Alpha Blending”

Option "ALL/1/General/FbBlendOvl" "1"

Note: You must install the GStreamer plugin before using this function.

You can also configure through the EMGD-CED while generating the driver package by selecting Enable framebuffer overlay blending in the Linux option page (see Linux Options Page).

Following are some examples on GStreamer commands with subtitle option:

• For SRT file:

gst-launch filesrc location=subtitle.srt ! subparse ! txt. filesrc location=video.wmv ! asfdemux ! queue ! MixVideoDecoderWMV ! vatextoverlay name=txt ! MixVideoSink

• For SMI file:

gst-launch filesrc location=subtitle.smi ! subparse ! txt. filesrc location=video.wmv ! asfdemux ! queue ! MixVideoDecoderWMV ! vatextoverlay name=txt ! MixVideoSink