Q：mediacode解码出来的数据的是在GPU上还是在cpu上？
A：https://source.android.com/devices/graphics/arch-bq-gralloc
结论应该是在RAM上，Gralloc内存分配器会分配内存给CPU、GPU。在使用过程中，传输内存句柄。

Q：使用的格式是什么？
A：YUV420/NV12 都有

Q：Android客户端能提供的数据是什么？
A：ByteBuffer buffer = codec.getOutputBuffers()
https://developer.android.com/reference/java/nio/ByteBuffer
PS：这里提供的是Direct buffers

Q： Android客户端期望接受的数据类型是什么？
A：

public interface I420Buffer extends Buffer {
ByteBuffer getDataY();
ByteBuffer getDataU();
ByteBuffer getDataV();
int getStrideY();
int getStrideU();
int getStrideV();
}

Q： 步骤能提供的数据和期望接受的数据类型可有转化的demo？
A：可以参考下面的实现。

private VideoFrame.Buffer copyI420Buffer(
    ByteBuffer buffer, int stride, int sliceHeight, int width, int height) {
if (stride % 2 != 0) {
    throw new AssertionError("Stride is not divisible by two: " + stride);
}
final int chromaWidth = (width + 1) / 2;
final int chromaHeight = (sliceHeight % 2 == 0) ? (height + 1) / 2 : height / 2;
final int uvStride = stride / 2;
final int yPos = 0;
final int yEnd = yPos + stride * height;
final int uPos = yPos + stride * sliceHeight;
final int uEnd = uPos + uvStride * chromaHeight;
final int vPos = uPos + uvStride * sliceHeight / 2;
final int vEnd = vPos + uvStride * chromaHeight;
I420Buffer frameBuffer = allocateI420Buffer(width, height);
buffer.limit(yEnd);
buffer.position(yPos);
copyPlane(
    buffer.slice(), stride, frameBuffer.getDataY(), frameBuffer.getStrideY(), width, height);
buffer.limit(uEnd);
buffer.position(uPos);
copyPlane(buffer.slice(), uvStride, frameBuffer.getDataU(), frameBuffer.getStrideU(),
    chromaWidth, chromaHeight);
if (sliceHeight % 2 == 1) {
    buffer.position(uPos + uvStride * (chromaHeight - 1)); // Seek to beginning of last full row.
    ByteBuffer dataU = frameBuffer.getDataU();
    dataU.position(frameBuffer.getStrideU() * chromaHeight); // Seek to beginning of last row.
    dataU.put(buffer); // Copy the last row.
}
buffer.limit(vEnd);
buffer.position(vPos);
copyPlane(buffer.slice(), uvStride, frameBuffer.getDataV(), frameBuffer.getStrideV(),
    chromaWidth, chromaHeight);
if (sliceHeight % 2 == 1) {
    buffer.position(vPos + uvStride * (chromaHeight - 1)); // Seek to beginning of last full row.
    ByteBuffer dataV = frameBuffer.getDataV();
    dataV.position(frameBuffer.getStrideV() * chromaHeight); // Seek to beginning of last row.
    dataV.put(buffer); // Copy the last row.
}
return frameBuffer;
}