Initial version of alpha channel support

This is a mostly-working implementation of an extra channel in the
bitstream. Configure with --enable-alpha to test. Notable TODOs:

 - Add extra channel to all mismatch tests, PSNR, SSIM, etc
 - Configurable subsampling
 - Variable number of planes (currently always uses all 4)
 - Loop filtering
 - Per-plane lossless quantizer
 - ARNR support

This implementation just uses the same contents as the Y channel
for the A channel, due to lack of content and general pain in
playing back 4 channel content. A later patch will use the actual
alpha channel passed in from outside the codec.

Change-Id: Ibf81f023b1c570bd84b3064e9b4b8ae52e087592

1 files changed, 7 insertions, 0 deletions

diff --git a/vp9/common/vp9_onyxc_int.h b/vp9/common/vp9_onyxc_int.h
index 2d4cd30cc..51bdb196b 100644
--- a/vp9/common/vp9_onyxc_int.h
+++ b/vp9/common/vp9_onyxc_int.h
@@ -124,6 +124,9 @@ typedef struct VP9Common {
 
   DECLARE_ALIGNED(16, int16_t, y_dequant[QINDEX_RANGE][2]);
   DECLARE_ALIGNED(16, int16_t, uv_dequant[QINDEX_RANGE][2]);
+#if CONFIG_ALPHA
+  DECLARE_ALIGNED(16, int16_t, a_dequant[QINDEX_RANGE][2]);
+#endif
 
   int width;
   int height;
@@ -187,6 +190,10 @@ typedef struct VP9Common {
   int y_dc_delta_q;
   int uv_dc_delta_q;
   int uv_ac_delta_q;
+#if CONFIG_ALPHA
+  int a_dc_delta_q;
+  int a_ac_delta_q;
+#endif
 
   unsigned int frames_since_golden;
   unsigned int frames_till_alt_ref_frame;