Multiple-resolution encoder

The example encoder down-samples the input video frames a number of
times with a down-sampling factor, and then encodes and outputs
bitstreams with different resolutions.

Support arbitrary down-sampling factor, and down-sampling factor
can be different for each encoding level.

For example, the encoder can be tested as follows.
1. Configure with multi-resolution encoding enabled:
../libvpx/configure --target=x86-linux-gcc --disable-codecs
--enable-vp8 --enable-runtime_cpu_detect --enable-debug
--disable-install-docs --enable-error-concealment
--enable-multi-res-encoding
2. Run make
3. Encode:
If input video is 1280x720, run:
./vp8_multi_resolution_encoder 1280 720 input.yuv 1.ivf 2.ivf 3.ivf 1
(output: 1.ivf(1280x720); 2.ivf(640x360); 3.ivf(320x180).
The last parameter is set to 1/0 to show/not show PSNR.)
4. Decode:
./simple_decoder 1.ivf 1.yuv
./simple_decoder 2.ivf 2.yuv
./simple_decoder 3.ivf 3.yuv
5. View video:
mplayer 1.yuv -demuxer rawvideo -rawvideo w=1280:h=720 -loop 0 -fps 30
mplayer 2.yuv -demuxer rawvideo -rawvideo w=640:h=360 -loop 0 -fps 30
mplayer 3.yuv -demuxer rawvideo -rawvideo w=320:h=180 -loop 0 -fps 30

The encoding parameters can be modified in vp8_multi_resolution_encoder.c,
for example, target bitrate, frame rate...

Modified API. John helped a lot with that. Thanks!

Change-Id: I03be9a51167eddf94399f92d269599fb3f3d54f5

examples.mk

@@ -96,6 +96,16 @@ GEN_EXAMPLES-$(CONFIG_VP8_ENCODER) += vp8cx_set_ref.c
 vp8cx_set_ref.GUID                  = C5E31F7F-96F6-48BD-BD3E-10EBF6E8057A
 vp8cx_set_ref.DESCRIPTION           = VP8 set encoder reference frame
 
+# C file is provided, not generated automatically.
+GEN_EXAMPLES-$(CONFIG_MULTI_RES_ENCODING) += vp8_multi_resolution_encoder.c
+vp8_multi_resolution_encoder.SRCS  \
+                         += third_party/libyuv/include/libyuv/basic_types.h  \
+                            third_party/libyuv/include/libyuv/cpu_id.h  \
+                            third_party/libyuv/include/libyuv/scale.h  \
+                            third_party/libyuv/source/scale.c  \
+                            third_party/libyuv/source/cpu_id.c
+vp8_multi_resolution_encoder.GUID         = 04f8738e-63c8-423b-90fa-7c2703a374de
+vp8_multi_resolution_encoder.DESCRIPTION  = VP8 Multiple-resolution Encoding
 
 # Handle extra library flags depending on codec configuration