Default to using VBR when a target bitrate is set, unless the max rate
is also set and matches the target. Changes to the Intel driver mean
that min_qp is also respected in this case, so set a codec default to
unset the value rather than using the current default inherited from
the MPEG-4 part 2 encoder.
Before this change, it was possible to overflow pic_order_cnt_lsb and
generate a stream with invalid POC numbering. This makes sure that
the field is large enough that a single IDR B* P sequence uses fewer
than half the available POC lsb values.
In H.264 section 8.2.1, we have that "The bitstream shall not contain
data that result in Min(TopFieldOrderCnt, BottomFieldOrderCnt) not
equal to 0 for a coded IDR frame". This fixes the encoder to always
conform to this - previously the POC values formed an unbroken
sequence, not resetting to zero on IDR frames.
Signed-off-by: Mark Thompson <sw@jkqxz.net>
This allows better checking of capabilities and will make it easier
to add more functionality later.
It also commonises some duplicated code around rate control setup
and adds more comments explaining the internals.
Move the NAL unit types into it. This will allow to stop including the
whole decoder-specific h264dec.h in some code that is unrelated to the
decoder and only needs some enum values.
Experimental; requires Skylake and VAAPI 0.39.1 (not yet released).
Also increases the allowed range of the quality option - in low-power
mode, the Intel driver supports levels 1-8 (and 0 meaning default).
Non-reference frames (nal_ref_idc == 0) should be discardable, so
frame_num does not advance after them. Before this change, a stream
containing unreferenced B-frames would be rejected by the reference
decoder.
Mark Thompson
Jun Zhao
Anton Khirnov
Vittorio Giovara