Only relevant for old ffmpeg versions.

AVFrame must be allocated with avcodec_alloc_frame().

This is the version present in Ubuntu Oneiric, the oldest distribution
with gcc 4.6.  Debian Squeeze is off target, because it has gcc 4.4,
which is unable to compile MPD anyway.

This commit drops all API compatibility hacks for older versions.

Hide the definition from C code, to prepare the transition to C++.

Implements Mantis feature request 3582.

Interleaving was completely wrong.  This code was never used, so it
didn't have an effect.

Works around assertion failure in decoder_timestamp().

Use av_get_sample_fmt_string() to obtain a human-readable string.

API simplification.

"Frame skipped" might cause the impression that the decoding of a whole
song failed.

This was disabled when compiled with a new ffmpeg version.  Older
ffmpeg versions used it explicitly, while newer ones may pass it
through from the codec.

Pass a callback table to scan_file() and scan_stream(), instead of
returning a tag object.

All supported ffmpeg/libav versions have this.

Implements support for libavcodec 0.9, which removes the compatibility
macros SAMPLE_FMT_*

Minor optimisation.

Use the tag_item_names table to look up the names of all MPD tags, and
remove the duplicate entries from ffmpeg_tag_maps.

Allow using this function without the ffmpeg_tag_map struct.

Eliminate some duplicate code.

Move the #ifdefs out of _copy_metadata().

No interest in this return value.

Require libavutil 51.5.0.

This function was added when the libavformat version was 53.2.0, but
the actual release 53.2.0 did not have it.

Needed for av_rescale_q() in ffmpeg 0.8.

avcodec_open() has been deprecated.

It's a no-op and deprecated.

For simpler seeking within current song.

Initialize the audio_format before calling avcodec_open(), because
avcodec_open() will fill bogus values.

Add GMutex, GCond attributes which will be used by callers to
conditionally wait on the stream.

Remove the (now-useless) plugin method buffer(), wait on GCond
instead.  Lock the input_stream before each method call.  Do the same
with the playlist plugins.

Let the codec start with fresh buffers.  This should fix the remaining
seeking issues.