[EGD-6497] Add audio transcoding framework

Add a mechanism to apply a data transform on the stream's input. An
example mono to stereo transform is provided.

Signed-off-by: Marcin Smoczyński <smoczynski.marcin@gmail.com>

module-audio/Audio/transcode/InputTranscodeProxy.cpp

@@ -0,0 +1,49 @@
+// Copyright (c) 2017-2021, Mudita Sp. z.o.o. All rights reserved.
+// For licensing, see https://github.com/mudita/MuditaOS/LICENSE.md
+
+#include "InputTranscodeProxy.hpp"
+#include "Transform.hpp"
+
+#include <utility>
+
+using audio::transcode::InputTranscodeProxy;
+
+InputTranscodeProxy::InputTranscodeProxy(AbstractStream &wrappedStream, Transform &transform) noexcept
+    : StreamProxy(wrappedStream), transform(transform),
+      transcodingSpaceSize(transform.getTransformSize(wrappedStream.getInputTraits().blockSize)),
+      transcodingSpace(std::make_unique<std::uint8_t[]>(transcodingSpaceSize)), transcodingSpaceSpan{
+                                                                                    .data     = transcodingSpace.get(),
+                                                                                    .dataSize = transcodingSpaceSize}
+{}
+
+bool InputTranscodeProxy::push(const Span &span)
+{
+    return getWrappedStream().push(transform.transform(span, transcodingSpaceSpan));
+}
+
+void InputTranscodeProxy::commit()
+{
+    transform.transform(peekedSpan, transcodingSpaceSpan);
+    getWrappedStream().commit();
+    peekedSpan.reset();
+}
+
+bool InputTranscodeProxy::peek(Span &span)
+{
+    auto result = getWrappedStream().peek(span);
+
+    if (result) {
+        peekedSpan = span;
+    }
+
+    return result;
+}
+
+auto InputTranscodeProxy::getInputTraits() const noexcept -> Traits
+{
+    auto originalTraits      = StreamProxy::getInputTraits();
+    auto transcodedFormat    = transform.transformFormat(originalTraits.format);
+    auto transcodedBlockSize = transform.transformBlockSize(originalTraits.blockSize);
+
+    return Traits{.blockSize = transcodedBlockSize, .format = transcodedFormat};
+}