Add automatic bit depth and speed selection for alsa devices. Set rat…

…e and format to "auto" by default. Always look for the greatest bit depth, but the lowest multiple of 44,100.

Improve support for big-endian CPUs by adding support for explicit -endian formats, i.e. S16_LE, S16_BE, S24_LE, S24_BE, S32_LE, S32_BE.

For the "disable_standby_mode" setting, change "while_active" to "auto".

activity_monitor.c

@@ -71,7 +71,7 @@ void going_active(int block) {
     shairport_sync_set_active(SHAIRPORT_SYNC(shairportSyncSkeleton), TRUE);
 #endif
 
-  if (config.disable_standby_mode == disable_standby_while_active) {
+  if (config.disable_standby_mode == disable_standby_auto) {
 #ifdef CONFIG_DBUS_INTERFACE
   if (dbus_service_is_running())
     shairport_sync_set_disable_standby(SHAIRPORT_SYNC(shairportSyncSkeleton), TRUE);
@@ -98,7 +98,7 @@ void going_inactive(int block) {
     shairport_sync_set_active(SHAIRPORT_SYNC(shairportSyncSkeleton), FALSE);
 #endif
 
-  if (config.disable_standby_mode == disable_standby_while_active) {
+  if (config.disable_standby_mode == disable_standby_auto) {
 #ifdef CONFIG_DBUS_INTERFACE
   if (dbus_service_is_running())
     shairport_sync_set_disable_standby(SHAIRPORT_SYNC(shairportSyncSkeleton), FALSE);

audio.h

@@ -18,6 +18,8 @@ typedef struct {
   int (*init)(int argc, char **argv);
   // at end of program
   void (*deinit)(void);
+
+  int (*prepare)(void); // looks and sets stuff in the config data structure
 
   void (*start)(int sample_rate, int sample_format);