For libavcodec 59 support.

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

av_demuxer_iterate() was added in libavformat 58.9.100.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1178

Regression by commit a22d1c88

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1097

To be reused by the FFmpeg filter plugin.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/892

This implements the feature that was missing/broken in this bug
report: https://github.com/MusicPlayerDaemon/MPD/issues/930

Prepare for an implementation without InputStream.

Bug #915 is about an I/O exception thrown where none was allowed,
leading to crash via std::terminate().  However, instead of catching
and logging the error inside the decoder plugin, it should be able to
propagate the I/O error to the MPD core, so MPD can avoid trying other
decoder plugins.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/915

This reverts commit eb192137.

This is no longer necessary because we require FFmpeg 3.1 or newer
since MPD 0.21.2.

This fixes a deprecation warning because the implicit AVPacket copy
constructor copies the deprecated attribute `convergence_duration`.

The former was deprecated with C++14.

According to the C++11 and C++17 standards, both files are identical.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with bugprone-suspicious-missing-comma
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Add a `constexpr` constructor and several `constexpr` methods to
construct a DecoderPlugin at compile time, in a way which allows
adding new methods later without having to edit each plugin.

Don't catch and log exceptions.  Let the caller handle the error.

Since we switched from autotools to Meson in commit
94592c14, we don't need to include
`config.h` early to properly enable large file support.  Meson passes
the required macros on the compiler command line instead of defining
them in `config.h`.

This means we can include `config.h` at any time, whenever we want to
check its macros, and there are no ordering constraints.

`AVCodecParameters` contains values from the codec detected by
avformat_find_stream_info(), but after avcodec_open2(), a different
codec might be selected with a different `AVSampleFormat`.  This leads
to misinterpretation of data returned from FFmpeg, leading to random
noise or silence.

This was observed with FFmpeg 4.0.2 and a TS container file containing
MP2.  A mp3-float codec was detected returning `AV_SAMPLE_FMT_FLTP`,
but finally the `mpegaudiodec_fixed.c` was used, returning
`AV_SAMPLE_FMT_S16`.

By using the audio format from `AVCodecContext`, we ensure that MPD
and FFmpeg always agree on the actual audio format in the buffer.

This removes the FFmpeg bug workaround from commit e1b032cb which I
assume is obsolete after 7 years.

Fixes #380

Drop some compatibility code.

This is the version in Debian Jessie (oldstable).

This is kind of a revert of commit
b2e3c075, which is not any longer
necessary since commit 0dd4b52b
removed the last call to `av_open_input_stream()`.