X-Git-Url: https://git.stderr.nl/gitweb?a=blobdiff_plain;f=libchimara%2Fschannel.c;h=617adc19eb90b46736ecf817468beadf7db6c80b;hb=ac51488902551bd4badb553e3f7215220dc68924;hp=d176d7d87caf7ef04aa878340aea32943863b2a1;hpb=1461483626f28b52f8f9f3cc350f9cb330579285;p=projects%2Fchimara%2Fchimara.git
diff --git a/libchimara/schannel.c b/libchimara/schannel.c
index d176d7d..617adc1 100644
--- a/libchimara/schannel.c
+++ b/libchimara/schannel.c
@@ -172,6 +172,23 @@ finally:
* Remember that it is possible that the library will be unable to create a new
* channel, in which case glk_schannel_create() will return %NULL.
*
+ * When you create a channel using glk_schannel_create(), it has full volume,
+ * represented by the value 0x10000. Half volume would be 0x8000, three-quarters
+ * volume would be 0xC000, and so on. A volume of zero represents silence.
+ *
+ * You can overdrive the volume of a channel by setting a volume greater than
+ * 0x10000. However, this is not recommended; the library may be unable to
+ * increase the volume past full, or the sound may become distorted. You should
+ * always create sound resources with the maximum volume you will need, and then
+ * reduce the volume when appropriate using the channel-volume calls.
+ *
+ *
+ * Mathematically, these volume changes should be taken as linear
+ * multiplication of a waveform represented as linear samples. As I
+ * understand it, linear PCM encodes the sound pressure, and therefore a
+ * volume of 0x8000 should represent a 6 dB drop.
+ *
+ *
* Returns: A new sound channel, or %NULL.
*/
schanid_t
@@ -185,11 +202,14 @@ glk_schannel_create(glui32 rock)
* @rock: The rock value to give the new sound channel.
* @volume: Integer representing the volume; 0x10000 is 100%.
*
- * [DRAFT SPEC]
- *
* The glk_schannel_create_ext() call lets you create a channel with the volume
* already set at a given level.
*
+ * Not all libraries support glk_schannel_create_ext(). You should test the
+ * %gestalt_Sound2 selector before you rely on it; see Testing for Sound
+ * Capabilities.
+ *
* Returns: A new sound channel, or %NULL.
*/
schanid_t
@@ -402,9 +422,14 @@ glk_schannel_play(schanid_t chan, glui32 snd)
* sound is playing, there will be no notification event.
*
* Not all libraries support sound notification. You should test the
- * %gestalt_SoundNotify selector before you rely on it; see Testing for Sound
* Capabilities.
+ *
+ * Note that you can play a sound on a channel whose volume is zero. This has
+ * no audible result, unless you later change the volume; but it produces
+ * notifications as usual. You can also play a sound on a paused channel; the
+ * sound is paused immediately, and does not progress.
*
* Returns: 1 on success, 0 on failure.
*/
@@ -482,8 +507,6 @@ glk_schannel_play_ext(schanid_t chan, glui32 snd, glui32 repeats, glui32 notify)
* @sndarray: Array of sound resource numbers.
* @soundcount: Length of @sndarray, must be equal to @chanarray.
* @notify: If nonzero, request a notification when each sound finishes.
- *
- * [DRAFT SPEC]
*
* This works the same as glk_schannel_play_ext(), except that you can specify
* more than one sound. The channel references and sound resource numbers are
@@ -496,6 +519,11 @@ glk_schannel_play_ext(schanid_t chan, glui32 snd, glui32 repeats, glui32 notify)
* a number from 0 to @soundcount.)
*
*
+ * If the @notify argument is nonzero, you will get a separate sound
+ * notification event as each sound finishes. They will all have the same
+ * @val2 value.
+ *
+ *
* Note that you have to supply @chancount and @soundcount as separate
* arguments, even though they are required to be the same. This is an awkward
* consequence of the way array arguments are dispatched in Glulx.
@@ -610,9 +638,7 @@ glk_schannel_stop(schanid_t chan)
/**
* glk_schannel_pause:
* @chan: Channel to pause.
- *
- * [DRAFT SPEC]
- *
+ *
* Pause any sound playing in the channel. This does not generate any
* notification events. If the channel is already paused, this does nothing.
*
@@ -649,11 +675,16 @@ glk_schannel_pause(schanid_t chan)
/**
* glk_schannel_unpause:
* @chan: Channel to unpause.
- *
- * [DRAFT SPEC]
*
* Unpause the channel. Any paused sounds begin playing where they left off. If
* the channel is not already paused, this does nothing.
+ *
+ *
+ * This means, for example, that you can pause a channel that is currently
+ * not playing any sounds. If you then add a sound to the channel, it will
+ * not start playing; it will be paused at its beginning. If you later
+ * unpaise the channel, the sound will commence.
+ *
*/
void
glk_schannel_unpause(schanid_t chan)
@@ -685,19 +716,20 @@ glk_schannel_unpause(schanid_t chan)
* @chan: Channel to set the volume of.
* @vol: Integer representing the volume; 0x10000 is 100%.
*
- * Sets the volume in the channel. When you create a channel, it has full
- * volume, represented by the value 0x10000. Half volume would be 0x8000,
- * three-quarters volume would be 0xC000, and so on. A volume of zero represents
- * silence, although the sound is still considered to be playing.
+ * Sets the volume in the channel, from 0 (silence) to 0x10000 (full volume).
+ * Again, you can overdrive the volume by setting a value greater than 0x10000,
+ * but this is not recommended.
*
- * You can call this function between sounds, or while a sound is playing. The
- * effect is immediate.
+ * The glk_schannel_set_volume() function does not include duration and notify
+ * values. Both are assumed to be zero: immediate change, no notification.
+ *
+ * You can call this function between sounds, or while a sound is playing.
+ * However, a zero-duration change while a sound is playing may produce
+ * unpleasant clicks.
*
- * You can overdrive the volume of a channel by setting a volume greater than
- * 0x10000. However, this is not recommended; the library may be unable to
- * increase the volume past full, or the sound may become distorted. You should
- * always create sound resources with the maximum volume you will need, and then
- * call glk_schannel_set_volume() to reduce the volume when appropriate.
+ * At most one volume change can be occurring on a sound channel at any time.
+ * If you call this function while a previous volume change is in progress, the
+ * previous change is interrupted.
*
* Not all libraries support this function. You should test the
* %gestalt_SoundVolume selector before you rely on it; see