shout: introduce pluggable encoder API

I've perhaps gone a bit overboard, but here's the current rundown:

Both Ogg and MP3 use the "shout" audio output plugin.  The shout audio
output plugin itself has two new plugins, one for the Ogg encoder,
and another for the MP3 (LAME) encoder.

Configuration for an Ogg stream doesn't change.  For an MP3 stream,
configuration is the same as Ogg, with two exceptions.  First, you must
specify the optional "encoding" parameter, which should be set to "mp3".
See mpd.conf(5) for more details.  Second, the "quality" parameter is
reversed for LAME, such that 1 is high quality for LAME, whereas 10 is
high quality for Ogg.

I've decomposed the code so that all libshout related operations
are done in audioOutput_shout.c, all Ogg specific functions are in
audioOutput_shout_ogg.c, and of course then all LAME specific functions
are handled in audioOutput_shout_mp3.c.

To develop encoder plugins for the shout audio output plugin, I basically
just mimicked the plugin system used for audio outputs.  This might be
overkill, but hopefully if anyone ever wants to support some other sort
of stream, like maybe AAC, FLAC, or WMA (hey it could happen), they will
hopefully be all set.

The Ogg encoder is slightly less optimal under this configuration.
It used to send shout data directly out of its ogg_page structures.  Now,
in the interest of encapsulation, it copies the data from its ogg_page
structures into a buffer provided by the shout audio output plugin (see
audioOutput_shout_ogg.c, line 77.)  I suspect the performance impact
is negligible.

As for metadata, I'm pretty sure they'll both work.  I wrote up a test
scaffold that would create a fake tag, and tell the plugin to send it
out to the stream every few seconds.  It seemed to work fine.  Of course,
if something does break, I'll be glad to fix it.

Lastly, I've renamed lots of things into snake_case, in keeping with
normalperson's wishes in that regard.

[mk: moved the MP3 patch after this one.  Splitted this patch into
several parts; the others were already applied before this one.  Fixed
a bunch GCC warnings and wrong whitespace modifications.  Made it
compile with mpd-mk by adapting to its prototypes]

1 files changed, 35 insertions, 29 deletions

diff --git a/src/audioOutputs/audioOutput_shout.h b/src/audioOutputs/audioOutput_shout.h
index eee2ccad2..c21ddff40 100644
--- a/src/audioOutputs/audioOutput_shout.h
+++ b/src/audioOutputs/audioOutput_shout.h
@@ -27,7 +27,38 @@
 #include "../timer.h"
 
 #include <shout/shout.h>
-#include <vorbis/vorbisenc.h>
+
+#define DISABLED_SHOUT_ENCODER_PLUGIN(plugin) shout_encoder_plugin plugin;
+
+typedef struct shout_data shout_data;
+
+typedef int (*shout_encoder_clear_encoder_func) (shout_data * sd);
+typedef int (*shout_encoder_encode_func) (shout_data * sd,
+					  const char * chunk,
+					  size_t len);
+typedef void (*shout_encoder_finish_func) (shout_data * sd);
+typedef int (*shout_encoder_init_func) (shout_data * sd);
+typedef int (*shout_encoder_init_encoder_func) (shout_data * sd);
+/* Called when there is a new MpdTag to encode into the stream.  If
+   this function returns non-zero, then the resulting song will be
+   passed to the shout server as metadata.  This allows the Ogg
+   encoder to send metadata via Vorbis comments in the stream, while
+   an MP3 encoder can use the Shout Server's metadata API. */
+typedef int (*shout_encoder_send_metadata_func) (shout_data * sd,
+						 char * song,
+						 size_t size);
+
+typedef struct _shout_encoder_plugin {
+	const char *name;
+	unsigned int shout_format;
+
+	shout_encoder_clear_encoder_func clear_encoder_func;
+	shout_encoder_encode_func encode_func;
+	shout_encoder_finish_func finish_func;
+	shout_encoder_init_func init_func;
+	shout_encoder_init_encoder_func init_encoder_func;
+	shout_encoder_send_metadata_func send_metadata_func;
+} shout_encoder_plugin;
 
 typedef struct _shout_buffer {
 	unsigned char *data;
@@ -35,26 +66,13 @@ typedef struct _shout_buffer {
 	size_t max_len;
 } shout_buffer;
 
-typedef struct _ogg_vorbis_data {
-	ogg_stream_state os;
-	ogg_page og;
-	ogg_packet op;
-	ogg_packet header_main;
-	ogg_packet header_comments;
-	ogg_packet header_codebooks;
-
-	vorbis_dsp_state vd;
-	vorbis_block vb;
-	vorbis_info vi;
-	vorbis_comment vc;
-} ogg_vorbis_data;
-
 struct shout_data {
 	shout_t *shout_conn;
 	shout_metadata_t *shout_meta;
 	int shout_error;
 
-	ogg_vorbis_data od;
+	shout_encoder_plugin *encoder;
+	void *encoder_data;
 
 	float quality;
 	int bitrate;
@@ -76,19 +94,7 @@ struct shout_data {
 	shout_buffer buf;
 };
 
-void copy_tag_to_vorbis_comment(struct shout_data *sd);
-
-int send_ogg_vorbis_header(struct shout_data *sd);
-
-int shout_ogg_encoder_clear_encoder(struct shout_data *sd);
-
-int init_encoder(struct shout_data *sd);
-
-int shout_ogg_encoder_send_metadata(struct shout_data * sd,
-				    char *song, size_t size);
-
-void shout_ogg_encoder_encode(struct shout_data *sd,
-			      const char *chunk, size_t len);
+extern shout_encoder_plugin shout_ogg_encoder;
 
 #endif