Previously, FFmpeg decoders needed to wait for the initial index to finish
before they could retrieve frames. Now they can retrieve frames while the
index is occurring, provided the appropriate frame has already been indexed (if
not, the retrieve will need to wait still).
Our renderer system is already heavily multithreaded and prioritized to keep the
main thread active. As a result, FFmpeg receives little benefits from being
multithreaded and is actually detrimental to our main thread as it hasn't been
prioritized to keep the main thread as active as possible.
We use Qt's built in zlib compression on the fastest setting (it was found that
higher compression took 5x as long with a negligible decrease in size). This
helps keep disk cache sizes low.
While there are clear efficiencies in storing the frame out of the codec,
there's little benefit to storing it in a format higher than its native pixel
format since the pixel conversion is generally fairly quick. This commit will
index all frames in their native pixel format.
A few commits ago, the render behavior was changed to only render within a
user-specified range of the playhead. This works well, but it would still
render from the start of the range (usually before the playhead) to the end,
meaning it couldn't keep up with the playhead as well as it should. This
commit prioritizes frames close to the playhead and renders outwards to
address this.
This index system will have awareness of the disk cache state and be able to
fill in and store frames as necessary while keeping the disk cache under
user defined limits.
itsmattkc