Closes https://github.com/MusicPlayerDaemon/MPD/issues/1233

Insert an "aformat" filter which converts double-precision to
single-precision.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1235

If DetectFilterOutputFormat() fails to determine the output format,
insert an "aformat" filter which attempts to force a specific output
format.

Fixes part 2 of of https://github.com/MusicPlayerDaemon/MPD/issues/1235

Merge some duplicate code.

Since AVFilterContext are freed automatically, this wrapper class
serves no purpose.  Let's remove it.

Fixes potential double-free bugs which currently did not occur because
the destructors happened to be called in the right order.

Fixes part 1 of https://github.com/MusicPlayerDaemon/MPD/issues/1235

The type is duplicated otherwise

Found with modernize-use-auto
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with readability-const-return-type
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with readability-use-anyofallof
Signed-off-by: Rosen Penev <rosenp@gmail.com>

loop is wrong anyway. It's missing a break;
Signed-off-by: Rosen Penev <rosenp@gmail.com>

The latter is easier to read and is the "correct" thing to do.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Prevent a segfault when accessing album art.

Fix #1224 #1225

Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with cppcoreguidelines-avoid-non-const-global-variables
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with modernize-use-default
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Don't truncate the FILETIME to second resolution to pass it to
std::chrono::system_clock::from_time_t(); instead, calculate the
offset between the FILETIME epoch and the
std::system_clock::time_point epoch, and use that to initialize the
time_point directly.

This avoids underruns at the start of playback.

This was missing in commit 8a243e6e