6d91b5c7 ("fix double promotions") changed
how LAME peak values are decoded, producing large incorrect values that
cause some MP3 files to play silently.

Restore the original decode from MAD fixed-point format to double and
document what it's doing.

Fixes #1823

This should prevent ffmpeg from taking priority over the gme plugin.
The ffmpeg plugin is more buggy than gme.
One of the prominent bugs of preferring ffmpeg over gme is that ffmpeg
cannot seek SAP files while gme can. This should prevent that from
happening.

This allows dropping a few compile-time version checks and we can use
pkg-config to detect the library.

When drop_start_samples and drop_end_samples overlap and are greater
than the actual number of samples, the `num_samples` calculation in
SubmitPCM() could underflow.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1712

Fixes compiler warning because formatting unscoped enums is deprecated
since libfmt 9.

Commit ebae25d1 added that #include, but forgot to wrap it in
"extern C", so the linker tried to look up C++ symbols, causing linker
failure.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1582

This disables a long delay for playing songs from the cdio_paranoia
input plugin if ReplayGain is enabled.

This issue occurs when playing HLS streaming delivered
from a server that does not support partial requests.
The issue is reproduced as follows(using Ubuntu 20.04 PC):

1. Prepare HLS example content.

$ mkdir test
$ ffmpeg -i example.flac -vn -c:a aac -b:a 128000 -f hls -hls_list_size 0 test/output.m3u8
(ffmpeg 4.2.4 is used)

2. Prepare web server without partial requests support.
(Docker version 20.10.12 and NGINX official Docker image is used)

$ docker run --name tmp-nginx-container -d nginx
$ docker cp tmp-nginx-container:/etc/nginx/conf.d/default.conf .
$ docker rm -f tmp-nginx-container

Edit default.conf and add "max_ranges 0;" to "location / {...}".
This disables partial requests support,
removes 'Accept-Ranges: bytes' header from the server response.
Then, run the server:

$ docker run --name test-nginx -v $PWD/test:/usr/share/nginx/html:ro -v $PWD/default.conf:/etc/nginx/conf.d/default.conf -d -p 8080:80 nginx

3. Setup MPD to Play the next URL.

http://address-of-the-server:8080/output.m3u8

Seeking this stream results in "exception: Not seekable".

AVFMTCTX_UNSEEKABLE signals the stream is not seekable
according to FFmpeg source code description:
https://github.com/FFmpeg/FFmpeg/blob/8e98dfc57fd05c49095dd964456a7acbb6da634c/libavformat/avformat.h#L1181

Fixes part 1 of https://github.com/MusicPlayerDaemon/MPD/issues/1490

ffmpeg from current git master no longer exposes
av_malloc() nor av_free() through other included
headers. directly include libavutil/mem.h to fix
compilation with (as-yet-unreleased) ffmpeg.

This part of the AVIOContext API is not documented :-(

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1448

Don't return early from ScanOpusTags() if only
TagHandler::WantPicture() is set.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1413

Fixes MixRamp failures when a MP3 file has two ID3 tags, one of them
without MixRamp.

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

SonarLint reports the latter to be better:

std::scoped_lock basically provides the same feature as std::lock_guard,
but is more generic: It can lock several mutexes at the same time, with a
deadlock prevention mechanism (see {rule:cpp:S5524}). The equivalent code
to perform simultaneous locking with std::lock_guard is significantly more
complex. Therefore, it is simpler to use std::scoped_lock all the time,
even when locking only one mutex (there will be no performance impact).
Signed-off-by: Rosen Penev <rosenp@gmail.com>

C arrays can be used with make_unique in C++17.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

For libavcodec 59 support.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1333

Unlike GetFilenameSuffix(), uri_get_suffix() removes the query string
first, which breaks file names with question marks in the name.
Therefore, uri_get_suffix() shall only be applied to remote URIs.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1316

The wrong variable was used.  This has been broken by commit
4eeea640 seven years ago - and nobody as noticed, d'oh!

Fixes crash bug.

make_pair is an old C++98 function that can be replaced by modern
shorter constructs.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

These should be equivalent anyway.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

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

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

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

If UpdateStreamTag() gets called while an initial seek is pending, the
result will never be submitted to a MusicChunk.  By avoiding the
UpdateStreamTag() call in that case (by moving UpdateStreamTag() to
after the PrepareInitialSeek() check), the song_tag is preserved until
UpdateStreamTag() is called again from SubmitData().

This fixes missing tags in the "httpd" output.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1137