baseparse: enhancements for timestamp marked framed formats
baseparse: enhancements for timestamp marked framed formats

That is, as such formats allow subclass to extract position from frame,
it is possible to extract duration (if not otherwise provided)
from (near) last frame, and a seek can fairly accurately target the required
position.

Fixes #631389.

ylatuya/gstreamer,lovebug356/gstreamer,justinjoy/gstreamer,shelsonjava/gstreamer,krichter722/gstreamer,jpxiong/gstreamer,shelsonjava/gstreamer,cfoch/gstreamer,jpxiong/gstreamer,ensonic/gstreamer,shelsonjava/gstreamer,mparis/gstreamer,Distrotech/gstreamer,krieger-od/gstreamer,drothlis/gstreamer,cfoch/gstreamer,StreamUtils/gstreamer,centricular/gstreamer,drothlis/gstreamer,collects/gstreamer,ensonic/gstreamer,cablelabs/gstreamer,Lachann/gstreamer,magcius/gstreamer,magcius/gstreamer,krieger-od/gstreamer,ensonic/gstreamer,cablelabs/gstreamer,Lachann/gstreamer,krichter722/gstreamer,drothlis/gstreamer,ahmedammar/platform_external_gst_gstreamer,Distrotech/gstreamer,ylatuya/gstreamer,Lachann/gstreamer,StreamUtils/gstreamer,mparis/gstreamer,surround-io/gstreamer,drothlis/gstreamer,lubosz/gstreamer,surround-io/gstreamer,ensonic/gstreamer,cablelabs/gstreamer,collects/gstreamer,centricular/gstreamer,magcius/gstreamer,cfoch/gstreamer,jpakkane/gstreamer,surround-io/gstreamer,justinjoy/gstreamer,Lachann/gstreamer,shelsonjava/gstreamer,krieger-od/gstreamer,ylatuya/gstreamer,lovebug356/gstreamer,Distrotech/gstreamer,magcius/gstreamer,jpakkane/gstreamer,cablelabs/gstreamer,centricular/gstreamer,collects/gstreamer,lovebug356/gstreamer,jpakkane/gstreamer,ahmedammar/platform_external_gst_gstreamer,collects/gstreamer,drothlis/gstreamer,ahmedammar/platform_external_gst_gstreamer,lovebug356/gstreamer,mparis/gstreamer,jpxiong/gstreamer,ahmedammar/platform_external_gst_gstreamer,ahmedammar/platform_external_gst_gstreamer,surround-io/gstreamer,mparis/gstreamer,StreamUtils/gstreamer,magcius/gstreamer,justinjoy/gstreamer,krichter722/gstreamer,krieger-od/gstreamer,cfoch/gstreamer,ylatuya/gstreamer,StreamUtils/gstreamer,centricular/gstreamer,jpakkane/gstreamer,jpxiong/gstreamer,justinjoy/gstreamer,krichter722/gstreamer,Distrotech/gstreamer,krieger-od/gstreamer,mparis/gstreamer,jpxiong/gstreamer,Lachann/gstreamer,cablelabs/gstreamer,ensonic/gstreamer,centricular/gstreamer,collects/gstreamer,lubosz/gstreamer,justinjoy/gstreamer,cfoch/gstreamer,krichter722/gstreamer,Distrotech/gstreamer,StreamUtils/gstreamer,surround-io/gstreamer,lubosz/gstreamer,jpakkane/gstreamer,lubosz/gstreamer,ylatuya/gstreamer,lubosz/gstreamer,lovebug356/gstreamer,shelsonjava/gstreamer