swarmcalls: avoid grayscale video in macos

Change-Id: I5283d3a0459e031baa7eb0b1d481333aa683c79b

.gitignore

@@ -104,6 +104,7 @@ tools/.vscode/
 
 # Mac
 .DS_Store
+build-macos*
 
 # Android
 /build-android-*/

contrib/.gitignore

@@ -5,3 +5,4 @@ x86_64-*
 arm*
 aarch64*
 i686*
+apple*

src/media/video/video_mixer.cpp

@@ -469,6 +469,15 @@ VideoMixer::calc_position(std::unique_ptr<VideoMixerSource>& source,
     } else {
         cell_width = width_ / zoom;
         cell_height = height_ / zoom;
+
+        if (n == 1) {
+            // On some platforms (at least macOS/android) - Having one frame at the same
+            // size of the mixer cause it to be grey.
+            // Removing some pixels solve this. We use 16 because it's a multiple of 8
+            // (value that we prefer for video management)
+            cell_width -= 16;
+            cell_height -= 16;
+        }
     }
     if (currentLayout_ == Layout::ONE_BIG_WITH_SMALL) {
         if (index == 0) {
@@ -487,6 +496,11 @@ VideoMixer::calc_position(std::unique_ptr<VideoMixerSource>& source,
             cellW_off += (width_ - (n % zoom) * cell_width) / 2;
         }
         cellH_off = (index / zoom) * cell_height;
+        if (n == 1) {
+            // Centerize (cellwidth = width_ - 16)
+            cellW_off += 8;
+            cellH_off += 8;
+        }
     }
 
     // Compute frame size/position