Hello @athoik
There is no only one kind of "closed caption" - these one from your example file are not exposed as separate stream (they are not transmitted on separate PID), they are send in the H264 frames metadata.
So, just as logic suggests they should be returned in the callback by the video decoder.
As, you know video decoding is not handled by the exteplayer3. Video decoding is handled by video processing unit, let say "hardware" (/dev/dvb/adapter0/video0).
Theoretically, you can parse each H264/H265 NAL frame to search metadata with subtitles.
But I am not sure how big impact this will have on the performance.
Regards,
Sam