This can be useful in other places, e.g. it can replace objpool in
fftools.
The API is modified in the following nontrivial ways:
* opaque pointers can be passed through to all user callbacks
* read and write were previously separate callbacks in order to
accomodate the caller wishing to write a new reference to the FIFO and
keep the original one; the two callbacks are now merged into one, and
a flags argument is added that allows to request such behaviour on a
per-call basis
* new peek and drain functions
The per-frame reference picture set contains two more lists -
INTER_LAYER[01]. Assuming at most two layers, INTER_LAYER1 is always
empty, but is added anyway for completeness.
When inter-layer prediction is enabled, INTER_LAYER0 for the
second-layer frame will contain the base-layer frame from the same
access unit, if it exists.
The new lists are then used in per-slice reference picture set
construction as per F.8.3.4 "Decoding process for reference picture
lists construction".
Start by moving the DPB to it.
Only one context exists for now, so decoder behaviour should not change
with this commit, but that will change in the future.
Current code is written around the "simple" decode API's limitation that
a single input packet (AU/coded frame) triggers the output of at most
one output frame. However the spec contains two cases where a coded
frame may cause multiple frames to be output (cf. C.5.2.2.2):
* start of a new sequence
* overflowing sps_max_dec_pic_buffering
The decoder currently contains rather convoluted logic to handle these
cases:
* decode/output/per-frame sequence counters,
* HEVC_FRAME_FLAG_BUMPING
* ff_hevc_bump_frame()
* special clauses in ff_hevc_output_frame()
However, with the receive_frame() API none of that is necessary, as we
can just output multiple frames at once. Previously added ContainerFifo
allows that to be done in a straightforward and efficient manner.
Pass the only things required from it - slice header and PPS -
explicitly.
Will be useful in the following commits to avoid mofiying HEVCContext in
hls_slice_header().
Anton Khirnov