Don't return 0/-1 on success/error, but true/false.  Instead of int,
use bool for storing flags.

Stopping an audio output device without cancelling its buffer doesn't
make sense.  Combine the two operations, which saves several cancel
calls.

Don't return 0/-1 on success/error, but true/false.  Instead of int,
use bool for storing flags.

When the decoder exited before the buffer has grown big enough
("buffer_before_play"), the player thread waited forever.  Add an
additional check which disables buffering as soon as the decoder
exits.

The local variable "play_audio_format" is updated every time the
player starts playing a new song.  This way, we always know exactly
which audio format is current.  The old code broke when a new song had
a different format: ob.audio_format is the format of the next song,
not of the current one - using this caused breakage for the software
volume control.

Request the next song from the playlist (by clearing pc.next_song)
only if the player command is empty.  If it is not, the player may be
clearing the song that has already been queued, leading to an
assertion failure.

When the decoder failed to start, the function do_play() returned,
still having pc.command==PLAY.  This is because pc.command was reset
only when the decoder started up successfully.  Add another
player_command_finished() call in the error handler.

This bug caused the audio output devices to stay open, although MPD
wasn't playing: quitDecode() resetted player_control.command, assuming
that the command was STOP.  This way, player_task() didn't see the
CLOSE_AUDIO command, and the device was kept open.

Don't clear player_control.command in quitDecode().

Another partial frame fix: the silence buffer was 1020 bytes, which
had room for 127.5 24 bit stereo frames.  Don't send the partial last
frame in this case.

Renamed all functions which were still in CamelCase.

buffered_before_play was copied to struct player because it was used
to disable buffering when seeking.  Instead of mainaining a copy of
this number, move just the flag to the player struct.

QUEUE adds a new song to the player's queue.  CANCEL clears the queue.
These two commands replace the old and complex queueState and
queueLockState code.

The player struct holds the local variables which used to be passed to
all those helper functions in player_thread.c.

This variable is superfluous, it is only used to copy its value to
player_control.totalTime.  Since the original source of this value
(song->tag->time) will still be available at this point, we can safely
remove fileTime.

The decoder was woken up after each chunk which had been played.  That
caused a lot of superfluous context switches.  Wake up the decoder
only when a certain amount of the buffer has been consumed.  This
formula is somewhat arbitrary, and has to be proven experimentally.

This replaces the attributes bits, channels, sampleRate.

The last bit of CamelCase in audio_format.h.  Additionally, rename a
bunch of local variables.

CamelCase is ugly...  rename all functions.

"bool" should be used in C99 programs for boolean values.

Again, a data type which can be forward-declared.

pause() puts the audio output into pause mode: if supported, it may
perform a special action, which keeps the device open, but does not
play anything.  Output plugins like "shout" might want to play silence
during pause, so their clients won't be disconnected.  Plugins which
do not support pausing will simply be closed, and have to be reopened
when unpaused.

This pach includes an implementation for the shout plugin, which
sends silence chunks.

There was a known deadlocking bug in the notify library: when the
other thread set notify->pending after the according check in
notify_wait(), the latter thread was deadlocked.  Resolve this by
synchronizing all accesses to notify->pending with the notify object's
mutex.  Since notify_signal_sync() was never used, we can remove it.
As a consequence, we don't need notify_enter() and notify_leave()
anymore; eliminate them, too.

Get rid of CamelCase, and don't use a typedef, so we can
forward-declare it, and unclutter the include dependencies.

Give player.c a better name, meaning that the code is used to control
the player thread.

This is the last of the three variables.  Now we don't need
playerData.h anymore in most sources.

Now that "dc" is available here, we don't have to pass it to
decoder_is_idle() and decoder_is_starting() anymore.

decode() is a trivial wrapper for decodeParent().  Merge both and
rename them to do_play().

Unfortunately, we have to pass the DecoderControl pointer to these
inline functions, because the global variable "dc" may not be
available here.  This will be fixed later.

When dc->error!=NOERROR, we do not need to check state!=START.
Simplify the checks by moving the error check to the top.

The decoder thread is responsible for resetting dc->command after a
command was executed.  As a consequence, we can assume that
dc->command is already NONE after decoder_stop().

The source "decoder_control.c" provides an API for controlling the
decoder.  This replaces various direct accesses to the DecoderControl
struct.

playerKill() was marked as deprecated, but it seems like a good idea
to do proper cleanup in all threads (e.g. for usable valgrind
results).  Introduce the command "EXIT" which makes the player thread
exit cleanly.

playerWait() stops the player thread (twice!) and closes the output
device.  It should be well enough to just send CLOSE_AUDIO, without
STOP.

This requires a tiny change to the player thread code: make it break
when CLOSE_AUDIO is sent.

To make the code more consistent, call quitDecode() only at the end of
decodeParent().

Move code which runs in the player thread to player_thread.c.  Having
a lot of player thread code in decode.c isn't easy to understand.