Added VideoSourceDownSampler

VideoSourceDownSampler takes in a real video source. The MediaSource
interface is then implemented by shortcircuiting calls to this real source,
except for the read() function. For read we first call read of the real
source, then downsample the frame to the desired size and return that.

Change-Id: I6e1b377e043e136a70a7b03792eb9165bbe26398

1 files changed, 97 insertions, 0 deletions

diff --git a/include/media/stagefright/VideoSourceDownSampler.h b/include/media/stagefright/VideoSourceDownSampler.h
new file mode 100644
index 0000000..439918c
--- /dev/null
+++ b/include/media/stagefright/VideoSourceDownSampler.h
@@ -0,0 +1,97 @@
+/*
+ * Copyright (C) 2010 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// VideoSourceDownSampler implements the MediaSource interface,
+// downsampling frames provided from a real video source.
+
+#ifndef VIDEO_SOURCE_DOWN_SAMPLER_H_
+
+#define VIDEO_SOURCE_DOWN_SAMPLER_H_
+
+#include <media/stagefright/MediaSource.h>
+#include <utils/RefBase.h>
+
+namespace android {
+
+class IMemory;
+class MediaBuffer;
+class MetaData;
+
+class VideoSourceDownSampler : public MediaSource {
+public:
+    virtual ~VideoSourceDownSampler();
+
+    // Constructor:
+    // videoSource: The real video source which provides the original frames.
+    // width, height: The desired width, height. These should be less than or equal
+    // to those of the real video source. We then downsample the original frames to
+    // this size.
+    VideoSourceDownSampler(const sp<MediaSource> &videoSource,
+        int32_t width, int32_t height);
+
+    // MediaSource interface
+    virtual status_t start(MetaData *params = NULL);
+
+    virtual status_t stop();
+
+    virtual sp<MetaData> getFormat();
+
+    virtual status_t read(
+            MediaBuffer **buffer, const ReadOptions *options = NULL);
+
+    virtual status_t pause();
+
+private:
+    // Reference to the real video source.
+    sp<MediaSource> mRealVideoSource;
+
+    // Size of frames to be provided by this source.
+    int32_t mWidth;
+    int32_t mHeight;
+
+    // Size of frames provided by the real source.
+    int32_t mRealSourceWidth;
+    int32_t mRealSourceHeight;
+
+    // Down sampling paramters.
+    int32_t mDownSampleOffsetX;
+    int32_t mDownSampleOffsetY;
+    int32_t mDownSampleSkipX;
+    int32_t mDownSampleSkipY;
+
+    // True if we need to crop the still video image to get the video frame.
+    bool mNeedDownSampling;
+
+    // Meta data. This is a copy of the real source except for the width and
+    // height parameters.
+    sp<MetaData> mMeta;
+
+    // Computes the offset, skip parameters for downsampling the original frame
+    // to the desired size.
+    void computeDownSamplingParameters();
+
+    // Downsamples the frame in sourceBuffer to size (mWidth x mHeight). A new
+    // buffer is created which stores the downsampled image.
+    void downSampleYUVImage(const MediaBuffer &sourceBuffer, MediaBuffer **buffer) const;
+
+    // Disallow these.
+    VideoSourceDownSampler(const VideoSourceDownSampler &);
+    VideoSourceDownSampler &operator=(const VideoSourceDownSampler &);
+};
+
+}  // namespace android
+
+#endif  // VIDEO_SOURCE_DOWN_SAMPLER_H_