* 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.
+ *
+ * <note><para>
+ * 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.
+ * </para></note>
+ *
* Returns: A new sound channel, or %NULL.
*/
schanid_t
* @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 <link
+ * linkend="chimara-Testing-for-Sound-Capabilities">Testing for Sound
+ * Capabilities</link>.
+ *
* Returns: A new sound channel, or %NULL.
*/
schanid_t
* 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 <link
+ * %gestalt_Sound2 selector before you rely on it; see <link
* linkend="chimara-Testing-for-Sound-Capabilities">Testing for Sound
* Capabilities</link>.
+ *
+ * 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.
*/
* @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
* a number from 0 to @soundcount.)
*
* <note><para>
+ * 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.
+ * </para></note>
+ * <note><para>
* 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.
/**
* 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.
*
/**
* 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.
+ *
+ * <note><para>
+ * 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.
+ * </para></note>
*/
void
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 <link
* @vol: Integer representing the volume; 0x10000 is 100%.
* @duration: Length of volume change in milliseconds, or 0 for immediate.
* @notify: If nonzero, requests a notification when the volume change finishes.
- *
- * [DRAFT SPEC]
- *
+ *
* 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.
* event with type #evtype_VolumeNotify. The window will be %NULL, @val1 will be
* zero, and @val2 will be the nonzero value you passed as @notify.
*
- * The glk_schannel_set_volume() does not include @duration and @notify values.
- * Both are assumed to be zero: immediate change, no notification.
- *
- * You can call these functions between sounds, or while a sound is playing.
+ * 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.
*
* At most one volume change can be occurring on a sound channel at any time. If
- * you call one of these functions while a previous volume change is in
- * progress, the previous change is interrupted. The beginning point of the new
- * volume change should be wherever the previous volume change was interrupted
- * (rather than the previous change's beginning or ending point).
+ * you call this function while a previous volume change is in progress, the
+ * previous change is interrupted. The beginning point of the new volume change
+ * should be wherever the previous volume change was interrupted (rather than
+ * the previous change's beginning or ending point).
*
* Not all libraries support these functions. You should test the appropriate
* gestalt selectors before you rely on them; see "Testing for Sound
projects / projects / chimara / chimara.git / blobdiff