rv34: DC-only inverse transform

When decoding coefficients, detect whether the block is DC-only, and take
advantage of this knowledge to perform DC-only inverse transform.

This is achieved by:
- first, changing the 108x4 element modulo_three_table into a 108 element
  table (kind of base4), and accessing each value using mask and shifts.
- then, checking low bits for 0 (as they represent the presence of higher
  frequency coefficients)

Also provide x86 SIMD code for the DC-only inverse transform.

Signed-off-by: Kostya Shishkov <kostya.shishkov@gmail.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/libavcodec/rv34dsp.h b/libavcodec/rv34dsp.h
index f2bc20e911..6f53a09928 100644
--- a/libavcodec/rv34dsp.h
+++ b/libavcodec/rv34dsp.h
@@ -56,6 +56,7 @@ typedef struct RV34DSPContext {
     h264_chroma_mc_func avg_chroma_pixels_tab[3];
     rv40_weight_func rv40_weight_pixels_tab[2];
     rv34_inv_transform_func rv34_inv_transform_tab[2];
+    void (*rv34_inv_transform_dc_tab[2])(DCTELEM *block);
     rv40_weak_loop_filter_func rv40_weak_loop_filter[2];
     rv40_strong_loop_filter_func rv40_strong_loop_filter[2];
     rv40_loop_filter_strength_func rv40_loop_filter_strength[2];
@@ -66,6 +67,7 @@ void ff_rv34dsp_init(RV34DSPContext *c, DSPContext* dsp);
 void ff_rv40dsp_init(RV34DSPContext *c, DSPContext* dsp);
 
 void ff_rv34dsp_init_neon(RV34DSPContext *c, DSPContext *dsp);
+void ff_rv34dsp_init_x86(RV34DSPContext *c, DSPContext *dsp);
 
 void ff_rv40dsp_init_x86(RV34DSPContext *c, DSPContext *dsp);
 void ff_rv40dsp_init_neon(RV34DSPContext *c, DSPContext *dsp);