small cleanup of -db documentation

README.html

@@ -518,11 +518,12 @@ <h3 id="starting-and-running-uxplay">Starting and running UxPlay</h3>
 the audio played by the server.</li>
 </ul>
 <p>AirPlay volume-control attenuates volume (gain) by up to -30dB: the
-range -30dB:0dB can be rescaled from <em>Low</em>:0 (<em>Low</em> &lt;
-0), or <em>Low</em>:<em>High</em>, using the option
-“<code>-db _Low_</code>” or “<code>-db _Low_:_High_</code>” (Rescaling
-is linear in decibels). The option <code>-taper</code> provides a
-“tapered” AirPlay volume-control profile some users may prefer.</p>
+range -30dB:0dB can be rescaled from <em>Low</em>:0, or
+<em>Low</em>:<em>High</em>, using the option <code>-db</code> (“-db
+<em>Low</em>” or “-db <em>Low</em>:<em>High</em>”), <em>Low</em> must be
+negative. Rescaling is linear in decibels. The option
+<code>-taper</code> provides a “tapered” AirPlay volume-control profile
+some users may prefer.</p>
 <p>The -vsync and -async options also allow an optional positive (or
 negative) audio-delay adjustment in <em>milliseconds</em> for
 fine-tuning : <code>-vsync 20.5</code> delays audio relative to video by
@@ -1518,14 +1519,14 @@ <h3 id="mirror-screen-freezes-a-network-problem">5. Mirror screen
 introduced 2017, running tvOS 12.2.1), so it does not seem to matter
 what version UxPlay claims to be.</p>
 <h1 id="changelog">Changelog</h1>
-<p>1.68 2023-12-29 Introduced a simpler (default) method for generating
-a persistent public key from the server MAC address (which can now be
-set with the -m option). (The previous pem-file method is still
-available with -key option). New option -reg to maintain a register of
-pin-authenticated clients. Corrected volume-control: now inteprets
-AirPlay volume range -30dB:0dB as (gain/amplitude) decibel attenuation,
-with new option -db low[:high] for “flat” rescaling of the dB range. Add
--taper option for a “tapered” AirPlay volume-control profile.</p>
+<p>1.68 2023-12-31 New simpler (default) method for generating a
+persistent public key from the server MAC address (which can now be set
+with the -m option). (The previous method is still available with -key
+option). New option -reg to maintain a register of pin-authenticated
+clients. Corrected volume-control: now interprets AirPlay volume range
+-30dB:0dB as decibel gain attenuation, with new option -db low[:high]
+for “flat” rescaling of the dB range. Add -taper option for a “tapered”
+AirPlay volume-control profile.</p>
 <p>1.67 2023-11-30 Add support for Apple-style one-time pin
 authentication of clients with option “-pin”: (uses SRP6a authentication
 protocol and public key persistence). Detection with error message of

README.md

@@ -415,8 +415,8 @@ if you want to follow the Apple Music lyrics on the client while listening to su
 delays the video on the client to match audio on the server, so leads to
 a slight delay before a pause or track-change initiated on the client takes effect on the audio played by the server. 
 
-AirPlay volume-control attenuates volume (gain) by up to -30dB: the range -30dB:0dB can be rescaled from _Low_:0 (_Low_ < 0), or _Low_:_High_, using the
-option "`-db _Low_`" or "``-db _Low_:_High_``" (Rescaling is linear in decibels).   The option ```-taper``` provides a "tapered" AirPlay volume-control 
+AirPlay volume-control attenuates volume (gain) by up to -30dB: the range -30dB:0dB can be rescaled from _Low_:0, or _Low_:_High_, using the
+option  `-db` ("-db _Low_ " or "-db _Low_:_High_ "), _Low_ must be negative.  Rescaling is linear in decibels.   The option ```-taper``` provides a "tapered" AirPlay volume-control 
 profile some users may prefer.
 
 The -vsync and -async options
@@ -1194,10 +1194,10 @@ tvOS 12.2.1), so it does not seem to matter what version UxPlay claims to be.
 
 
 # Changelog
-1.68 2023-12-29   Introduced a simpler (default) method for generating a persistent public key from the server MAC 
-                  address (which can now be set with the -m option). (The previous pem-file method is still available 
+1.68 2023-12-31   New  simpler (default) method for generating a persistent public key from the server MAC 
+                  address (which can now be set with the -m option). (The previous method is still available 
                   with -key option).  New option -reg to maintain a register of pin-authenticated clients.   Corrected 
-                  volume-control: now inteprets AirPlay volume range -30dB:0dB as (gain/amplitude) decibel attenuation, 
+                  volume-control: now interprets AirPlay volume range -30dB:0dB as decibel gain attenuation, 
                   with new option -db low[:high] for "flat" rescaling of the dB range. Add -taper option for a "tapered"
                   AirPlay volume-control profile.
 

README.txt

@@ -511,10 +511,10 @@ helped to prevent this previously when timestamps were not being used.)
     takes effect on the audio played by the server.
 
 AirPlay volume-control attenuates volume (gain) by up to -30dB: the
-range -30dB:0dB can be rescaled from *Low*:0 (*Low* \< 0), or
-*Low*:*High*, using the option "`-db _Low_`" or "`-db _Low_:_High_`"
-(Rescaling is linear in decibels). The option `-taper` provides a
-"tapered" AirPlay volume-control profile some users may prefer.
+range -30dB:0dB can be rescaled from *Low*:0, or *Low*:*High*, using the
+option `-db` ("-db *Low*" or "-db *Low*:*High*"), *Low* must be
+negative. Rescaling is linear in decibels. The option `-taper` provides
+a "tapered" AirPlay volume-control profile some users may prefer.
 
 The -vsync and -async options also allow an optional positive (or
 negative) audio-delay adjustment in *milliseconds* for fine-tuning :
@@ -1556,14 +1556,14 @@ what version UxPlay claims to be.
 
 # Changelog
 
-1.68 2023-12-29 Introduced a simpler (default) method for generating a
-persistent public key from the server MAC address (which can now be set
-with the -m option). (The previous pem-file method is still available
-with -key option). New option -reg to maintain a register of
-pin-authenticated clients. Corrected volume-control: now inteprets
-AirPlay volume range -30dB:0dB as (gain/amplitude) decibel attenuation,
-with new option -db low\[:high\] for "flat" rescaling of the dB range.
-Add -taper option for a "tapered" AirPlay volume-control profile.
+1.68 2023-12-31 New simpler (default) method for generating a persistent
+public key from the server MAC address (which can now be set with the -m
+option). (The previous method is still available with -key option). New
+option -reg to maintain a register of pin-authenticated clients.
+Corrected volume-control: now interprets AirPlay volume range -30dB:0dB
+as decibel gain attenuation, with new option -db low\[:high\] for "flat"
+rescaling of the dB range. Add -taper option for a "tapered" AirPlay
+volume-control profile.
 
 1.67 2023-11-30 Add support for Apple-style one-time pin authentication
 of clients with option "-pin": (uses SRP6a authentication protocol and

uxplay.cpp

@@ -1044,7 +1044,7 @@ static void parse_arguments (int argc, char *argv[]) {
                     continue;
                 }
             }
-            fprintf(stderr, "invalid argument -al %s: must be a decimal time offset in seconds, range [0,10]\n"
+            fprintf(stderr, "invalid -al %s: value must be a decimal time offset in seconds, range [0,10]\n"
                     "(like 5 or 4.8, which will be converted to a whole number of microseconds)\n", argv[i]);
             exit(1);
         } else if (arg == "-pin") {
@@ -1118,7 +1118,7 @@ static void parse_arguments (int argc, char *argv[]) {
                 }
             }
             if (db_bad) {
-	      fprintf(stderr, "%s %s requires argument \"low\" or \"low:high\" where low < 0 and high > low are decibel gain values\n", argv[i], start); 
+	      fprintf(stderr, "invalid %s %s: db value must be \"low\" or \"low:high\", low < 0 and high > low are decibel gains\n", argv[i], start); 
                 exit(1);
             }
 	    i++;