Multi-channels support for windows/mac/linux (#426)

* Add QUAD and QUAD_LFE layouts.

* Remove dual mono layout.

It makes no sense to have a case for those as the data structure
used (a bitmask) do not allow to represent this channel layout (a
channel can only be present once). As such it was a non-functional
layout

* Fix up cubeb_pulse compilation using C++ keyword.

* Remove the concept of preferred layout.

Channel layout is derived by the content being played. The concept of
preferred layout is meaningless. Either we have a layout defined, or
we don't. There's no in-between.

So we remove it.

* Remove CHANNEL_MONO concept.

* Add cubeb_sample_size convenience method.

* Rework cubeb_mixer.

This completely replace the existing remixer which had serious limitations:
1- Had no memory bound checks
2- Could only downmix 5.1 and 7.1 to stereo.

This mixer allows to convert from any sane layout to any other and work directly on interleaved samples.

This cubeb_mixer doesn't have an API compatible with the previous one.

This commit is non-fonctional, and was split for ease of review.

* Fix remixing on mac, windows and pulse backend.

* Make cubeb_mixer creation infallible.

Rather than ignore nonsensical layouts, we attempt to play it according to the stream channels count instead. The audio data will be played as-is, dropping the extra channels or inserting silence where needed.

* User proper sample size when calculating offsets.

Should the user data be of a different type to what the AudioUnit output is set to, we would have written outside the end of our allocated buffer.

* Fix input mixing and clarify frames vs samples terminology

* If a layout is unknown or invalid, always treat it as plain stereo or mono.

1 files changed, 4 insertions, 0 deletions

diff --git a/src/cubeb_utils.h b/src/cubeb_utils.h
index dc08fec..df67511 100644
--- a/src/cubeb_utils.h
+++ b/src/cubeb_utils.h
@@ -333,6 +333,10 @@ private:
   auto_array<T> ar;
 };
 
+extern "C" {
+  size_t cubeb_sample_size(cubeb_sample_format format);
+}
+
 using auto_lock = std::lock_guard<owned_critical_section>;
 #endif // __cplusplus