audio: make internal audio format 0 an invalid format

Having to use -1 for that is generally quite annoying.

Audio formats are created from bitmasks, and it can't be excluded that
0 is not a valid format. Fix this by adjusting AF_FORMAT_I so that it
is never 0. Along with AF_FORMAT_F and the special formats, all valid
formats are covered and guaranteed to be non-0.

It's possible that this commit will cause some regressions, as the
check for invalid audio formats changes a bit.

audio/filter/af_format.c

@@ -150,7 +150,7 @@ static int control(struct af_instance* af, int cmd, void* arg)
   }
   case AF_CONTROL_COMMAND_LINE:{
     int format = af_str2fmt_short(bstr0(arg));
-    if (format == -1) {
+    if (!format) {
       mp_msg(MSGT_AFILTER, MSGL_ERR, "[format] %s is not a valid format\n", (char *)arg);
       return AF_ERROR;
     }

audio/format.c

@@ -133,5 +133,5 @@ int af_str2fmt_short(bstr str)
         if (!bstrcasecmp0(str, af_fmtstr_table[i].name))
             return af_fmtstr_table[i].format;
 
-    return -1;
+    return 0;
 }

audio/format.h

@@ -43,11 +43,6 @@
 #define AF_FORMAT_US		(1<<1) // Unsigned
 #define AF_FORMAT_SIGN_MASK	(1<<1)
 
-// Fixed or floating point
-#define AF_FORMAT_I		(0<<2) // Int
-#define AF_FORMAT_F		(1<<2) // Foating point
-#define AF_FORMAT_POINT_MASK	(1<<2)
-
 // Bits used
 #define AF_FORMAT_8BIT		(0<<3)
 #define AF_FORMAT_16BIT		(1<<3)
@@ -62,7 +57,12 @@
 #define AF_FORMAT_IEC61937      (6<<6)
 #define AF_FORMAT_SPECIAL_MASK	(7<<6)
 
-#define AF_FORMAT_MASK          ((1<<9)-1)
+// Fixed or floating point
+#define AF_FORMAT_I             (1<<9) // Int
+#define AF_FORMAT_F             (2<<9) // Foating point
+#define AF_FORMAT_POINT_MASK    (3<<9)
+
+#define AF_FORMAT_MASK          ((1<<11)-1)
 
 // PREDEFINED formats
 
@@ -117,7 +117,7 @@
 #define AF_FORMAT_IEC61937_NE AF_FORMAT_IEC61937_LE
 #endif
 
-#define AF_FORMAT_UNKNOWN (-1)
+#define AF_FORMAT_UNKNOWN 0
 
 #define AF_FORMAT_IS_AC3(fmt) (((fmt) & AF_FORMAT_SPECIAL_MASK) == AF_FORMAT_AC3)
 #define AF_FORMAT_IS_IEC61937(fmt) (AF_FORMAT_IS_AC3(fmt) || ((fmt) & AF_FORMAT_SPECIAL_MASK) == AF_FORMAT_IEC61937)

mpvcore/m_option.c

@@ -1601,7 +1601,7 @@ static int parse_afmt(const m_option_t *opt, struct bstr name,
     }
 
     int fmt = af_str2fmt_short(param);
-    if (fmt == -1) {
+    if (!fmt) {
         mp_msg(MSGT_CFGPARSER, MSGL_ERR,
                "Option %.*s: unknown format name: '%.*s'\n",
                BSTR_P(name), BSTR_P(param));

mpvcore/options.c

@@ -802,7 +802,7 @@ const struct MPOpts mp_default_opts = {
     .sub_pos = 100,
     .sub_speed = 1.0,
     .audio_output_channels = MP_CHMAP_INIT_STEREO,
-    .audio_output_format = -1,  // AF_FORMAT_UNKNOWN
+    .audio_output_format = 0,  // AF_FORMAT_UNKNOWN
     .playback_speed = 1.,
     .movie_aspect = -1.,
     .field_dominance = -1,