fritsch/xbmc — comment on commit 9d7af6f7017e7f89abb097e5136d88151d1f1a9c
File: lib/ffmpeg/libavcodec/xvba_vc1.c line 38
By FernetMenta:

avctx->get_buffer, a callback to XBMC side will allocate this structure. [3] seems to be the pointer hwaccel decoders should store it (at least vaapi and dxva do so)