VSE: Adding a panning angle for multichannel audio.

The panning angle allows a more intuitive panning when the output is
surround sound. It sets the angle on the horizontal plane around the
listener. 0 degrees is to the front, negative values go to the left and
positive ones to the right. +/-180 degrees is directly from the back.

Technical detail: the panning value is linear with the panning angle
with a factor of 90 degrees. For stereo this means that -1 is left and
+1 right, since the speakers are exactly 90 degrees to either side.

Differential Revision: https://developer.blender.org/D12275

release/scripts/startup/bl_ui/space_sequencer.py

@@ -1659,7 +1659,7 @@ class SEQUENCER_PT_adjust_sound(SequencerButtonsPanel, Panel):
 
     def draw(self, context):
         layout = self.layout
-        layout.use_property_split = True
+        layout.use_property_split = False
 
         st = context.space_data
         strip = context.active_sequence_strip
@@ -1667,20 +1667,39 @@ class SEQUENCER_PT_adjust_sound(SequencerButtonsPanel, Panel):
 
         layout.active = not strip.mute
 
-        col = layout.column()
-
-        col.prop(strip, "volume", text="Volume")
-        col.prop(strip, "pitch")
-
-        col = layout.column()
-        col.prop(strip, "pan")
-        col.enabled = sound is not None and sound.use_mono
-
         if sound is not None:
             col = layout.column()
+
+            split = col.split(factor=0.4)
+            split.label(text="")
+            split.prop(sound, "use_mono")
             if st.waveform_display_type == 'DEFAULT_WAVEFORMS':
-                col.prop(strip, "show_waveform")
-            col.prop(sound, "use_mono")
+                split = col.split(factor=0.4)
+                split.label(text="")
+                split.prop(strip, "show_waveform")
+
+            col = layout.column()
+
+            split = col.split(factor=0.4)
+            split.alignment = 'RIGHT'
+            split.label(text="Volume")
+            split.prop(strip, "volume", text="")
+
+            split = col.split(factor=0.4)
+            split.alignment = 'RIGHT'
+            split.label(text="Pitch")
+            split.prop(strip, "pitch", text="")
+
+            split = col.split(factor=0.4)
+            split.alignment = 'RIGHT'
+            split.label(text="Pan")
+            audio_channels = context.scene.render.ffmpeg.audio_channels
+            pan_text = ""
+            if audio_channels != 'MONO' and audio_channels != 'STEREO':
+                pan_text = "%.2f°" % (strip.pan * 90)
+            split.prop(strip, "pan", text=pan_text)
+            split.enabled = sound.use_mono and audio_channels != 'MONO'
+
 
 
 class SEQUENCER_PT_adjust_comp(SequencerButtonsPanel, Panel):

source/blender/makesrna/intern/rna_sequencer.c

@@ -845,6 +845,17 @@ static void rna_Sequence_audio_update(Main *UNUSED(bmain), Scene *scene, Pointer
   DEG_id_tag_update(&scene->id, ID_RECALC_SEQUENCER_STRIPS);
 }
 
+static void rna_Sequence_pan_range(
+    PointerRNA *ptr, float *min, float *max, float *softmin, float *softmax)
+{
+  Scene *scene = (Scene *)ptr->owner_id;
+
+  *min = -FLT_MAX;
+  *max = FLT_MAX;
+  *softmax = 1 + (int)(scene->r.ffcodecdata.audio_channels > 2);
+  *softmin = -*softmax;
+}
+
 static int rna_Sequence_input_count_get(PointerRNA *ptr)
 {
   Sequence *seq = (Sequence *)(ptr->data);
@@ -2559,8 +2570,10 @@ static void rna_def_sound(BlenderRNA *brna)
 
   prop = RNA_def_property(srna, "pan", PROP_FLOAT, PROP_NONE);
   RNA_def_property_float_sdna(prop, NULL, "pan");
-  RNA_def_property_range(prop, -2.0f, 2.0f);
+  RNA_def_property_range(prop, -FLT_MAX, FLT_MAX);
+  RNA_def_property_ui_range(prop, -2, 2, 1, 2);
   RNA_def_property_ui_text(prop, "Pan", "Playback panning of the sound (only for Mono sources)");
+  RNA_def_property_float_funcs(prop, NULL, NULL, "rna_Sequence_pan_range");
   RNA_def_property_update(prop, NC_SCENE | ND_SEQUENCER, "rna_Sequence_audio_update");
 
   prop = RNA_def_property(srna, "show_waveform", PROP_BOOLEAN, PROP_NONE);