Bug 1475642 - Fix playback with some 3rd party audio cards. r=kinetik

Additional fix to bug 1469152

Differential Revision: https://phabricator.services.mozilla.com/D2131

--HG--
extra : moz-landing-system : lando

media/libcubeb/0002-Always-upmix-mono-to-the-first-two-channels-if-enoug.patch

@@ -1,17 +1,3 @@
-From dbd61924736fbe1a1caf1cbd544f7d197f1836f7 Mon Sep 17 00:00:00 2001
-From: Jean-Yves Avenard <jyavenard@mozilla.com>
-Date: Mon, 9 Jul 2018 20:10:13 +0200
-Subject: [PATCH 2/2] Always upmix mono to the first two channels if enough
- output channels are available
-
-This allows to output what people typically expect when playing mono audio: sound coming from both left and right channels.
-
-To force this conversion for happening on mac, we tag that layout are unknown as soon as a channel type is unknown
----
- src/cubeb_audiounit.cpp |  8 ++++++--
- src/cubeb_mixer.cpp     | 12 ++++++++++++
- 2 files changed, 18 insertions(+), 2 deletions(-)
-
 diff --git a/src/cubeb_audiounit.cpp b/src/cubeb_audiounit.cpp
 index 43120b3..5a83098 100644
 --- a/src/cubeb_audiounit.cpp
@@ -40,13 +26,13 @@ index 43120b3..5a83098 100644
  
    return cl;
 diff --git a/src/cubeb_mixer.cpp b/src/cubeb_mixer.cpp
-index 8995c55..9aa141d 100644
+index 8995c55..c95fef6 100644
 --- a/src/cubeb_mixer.cpp
 +++ b/src/cubeb_mixer.cpp
-@@ -533,6 +533,18 @@ struct cubeb_mixer
-         output_buffer += _context._out_ch_count - _context._in_ch_count;
-       }
-     } else {
+@@ -525,6 +525,19 @@ struct cubeb_mixer
+   {
+     if (_context._in_ch_count <= _context._out_ch_count) {
+       // Not enough channels to copy, fill the gaps with silence.
 +      if (_context._in_ch_count == 1 && _context._out_ch_count >= 2) {
 +        // Special case for upmixing mono input to stereo and more. We will
 +        // duplicate the mono channel to the first two channels. On most system,
@@ -54,14 +40,12 @@ index 8995c55..9aa141d 100644
 +        // expected that mono will on both left+right channels
 +        for (uint32_t i = 0; i < frames; i++) {
 +          output_buffer[0] = output_buffer[1] = *input_buffer;
-+          output_buffer += _context._out_ch_count ;
++          PodZero(output_buffer + 2, _context._out_ch_count - 2);
++          output_buffer += _context._out_ch_count;
 +          input_buffer++;
 +        }
 +        return;
 +      }
        for (uint32_t i = 0; i < frames; i++) {
-         PodCopy(output_buffer, input_buffer, _context._out_ch_count);
-         output_buffer += _context._out_ch_count;
--- 
-2.17.0
-
+         PodCopy(output_buffer, input_buffer, _context._in_ch_count);
+         output_buffer += _context._in_ch_count;

media/libcubeb/src/cubeb_mixer.cpp

@@ -525,6 +525,19 @@ struct cubeb_mixer
   {
     if (_context._in_ch_count <= _context._out_ch_count) {
       // Not enough channels to copy, fill the gaps with silence.
+      if (_context._in_ch_count == 1 && _context._out_ch_count >= 2) {
+        // Special case for upmixing mono input to stereo and more. We will
+        // duplicate the mono channel to the first two channels. On most system,
+        // the first two channels are for left and right. It is commonly
+        // expected that mono will on both left+right channels
+        for (uint32_t i = 0; i < frames; i++) {
+          output_buffer[0] = output_buffer[1] = *input_buffer;
+          PodZero(output_buffer + 2, _context._out_ch_count - 2);
+          output_buffer += _context._out_ch_count;
+          input_buffer++;
+        }
+        return;
+      }
       for (uint32_t i = 0; i < frames; i++) {
         PodCopy(output_buffer, input_buffer, _context._in_ch_count);
         output_buffer += _context._in_ch_count;
@@ -533,18 +546,6 @@ struct cubeb_mixer
         output_buffer += _context._out_ch_count - _context._in_ch_count;
       }
     } else {
-      if (_context._in_ch_count == 1 && _context._out_ch_count >= 2) {
-        // Special case for upmixing mono input to stereo and more. We will
-        // duplicate the mono channel to the first two channels. On most system,
-        // the first two channels are for left and right. It is commonly
-        // expected that mono will on both left+right channels
-        for (uint32_t i = 0; i < frames; i++) {
-          output_buffer[0] = output_buffer[1] = *input_buffer;
-          output_buffer += _context._out_ch_count ;
-          input_buffer++;
-        }
-        return;
-      }
       for (uint32_t i = 0; i < frames; i++) {
         PodCopy(output_buffer, input_buffer, _context._out_ch_count);
         output_buffer += _context._out_ch_count;