This duplicates the logic which FFmpeg's libavcodec uses. The effects
are unknown, though it's somewhat clear that a single thread doesn't
necessarily saturate a single CPU.
(Eventually we should just let FFmpeg auto-init the thread count, but
for now I prefer it this way, so e.g. verbose mode will print the
thread count.)
FFmpeg and Libav have the stupid practice of replacing and deprecating
API symbols on the same day. So with FFmpeg git, this is useless and
will print a compile time warning, while it's required with all stable
releases, and might lead to decoding errors with xvid/avi (apparently).
Add a comment before someone writes a patch and I have to explain it all
over again.
Our own code was introduced when FFmpeg didn't provide this API (or
maybe didn't even have a way to determine the CPU count). But now,
av_cpu_count() is available for all FFmpeg/Libav versions we support,
and there's no reason to have our own code.
libavutil's code seems to be slightly more sophisticated than our's, and
it's possible that the detected CPU count is different on some platforms
after this change.
This is a simplification, because it lets us use the AVPacket
functions, instead of handling the details manually.
It also allows the libavcodec rawvideo decoder to use reference
counting, so it doesn't have to memcpy() the full image data. The change
in av_common.c enables this.
This change is somewhat risky, because we rely on the following AVPacket
implementation details and assumptions:
- av_packet_ref() doesn't access the input padding, and just copies the
data. By the API, AVPacket is always padded, and we violate this. The
lavc implementation would have to go out of its way to make this a
real problem, though.
- We hope that the way we make the AVPacket refcountable in av_common.c
is actually supported API-usage. It's hard to tell whether it is.
Of course we still use our own "old" demux_packet struct, just so that
libav* API usage is somewhat isolated.
Use OPT_KEYVALUELIST() for all places where AVOptions are directly set
from mpv command line options. This allows escaping values, better
diagnostics (also no more "pal"), and somehow reduces code size.
Remove the old crappy option parser (av_opts.c).
wm4