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, 19 insertions, 1 deletions

diff --git a/vpx_scale/generic/yv12config.c b/vpx_scale/generic/yv12config.c
index 99e3543ac..632ff71f4 100644
--- a/vpx_scale/generic/yv12config.c
+++ b/vpx_scale/generic/yv12config.c
@@ -135,8 +135,19 @@ int vp9_realloc_frame_buffer(YV12_BUFFER_CONFIG *ybf,
     const int uv_border_w = border >> ss_x;
     const int uv_border_h = border >> ss_y;
     const int uvplane_size = (uv_height + 2 * uv_border_h) * uv_stride;
+#if CONFIG_ALPHA
+    const int alpha_width = aligned_width;
+    const int alpha_height = aligned_height;
+    const int alpha_stride = y_stride;
+    const int alpha_border_w = border;
+    const int alpha_border_h = border;
+    const int alpha_plane_size = (alpha_height + 2 * alpha_border_h) *
+                                 alpha_stride;
+    const int frame_size = yplane_size + 2 * uvplane_size +
+                           alpha_plane_size;
+#else
     const int frame_size = yplane_size + 2 * uvplane_size;
-
+#endif
     if (!ybf->buffer_alloc) {
       ybf->buffer_alloc = vpx_memalign(32, frame_size);
       ybf->buffer_alloc_sz = frame_size;
@@ -172,6 +183,13 @@ int vp9_realloc_frame_buffer(YV12_BUFFER_CONFIG *ybf,
     ybf->v_buffer = ybf->buffer_alloc + yplane_size + uvplane_size +
                     (uv_border_h * uv_stride) + uv_border_w;
 
+#if CONFIG_ALPHA
+    ybf->alpha_width = alpha_width;
+    ybf->alpha_height = alpha_height;
+    ybf->alpha_stride = alpha_stride;
+    ybf->alpha_buffer = ybf->buffer_alloc + yplane_size + 2 * uvplane_size +
+                        (alpha_border_h * alpha_stride) + alpha_border_w;
+#endif
     ybf->corrupted = 0; /* assume not currupted by errors */
     return 0;
   }