fftools/ffmpeg: change video decoding timestamp generation

When no timestamps are available from the container, the video decoding
code will currently use fake dts values - generated in
process_input_packet() based on a combination of information from the
decoder and the parser (obtained via the demuxer) - to generate
timestamps during decoder flushing. This is fragile, hard to follow, and
unnecessarily convoluted, since more reliable information can be
obtained directly from post-decoding values.

The new code keeps track of the last decoded frame pts and estimates its
duration based on a number of heuristics. Timestamps generated when both
pts and pkt_dts are missing are then simple pts+duration of the last frame.
The heuristics are somewhat complicated by the fact that lavf insists on
making up packet timestamps based on its highly incomplete information.
That should be removed in the future, allowing to further simplify this
code.

The results of the following tests change:
* h264-3386 now requires -fps_mode passthrough to avoid dropping frames
  at the end; this is a pathology of the interaction of the new and old
  code, and the fact that the sample switches from field to frame coding
  in the last packet, and will be fixed in following commits
* hevc-conformance-DELTAQP_A_BRCM_4 stops inventing an arbitrary
  timestamp gap at the end
* hevc-small422chroma - the single frame output by this test now has a
  timestamp of 0, rather than an arbitrary 7

0 files changed, 0 insertions, 0 deletions