pixlet: Fix architecture-dependent code and values

The constants used in the decoder used floating point precision,
and this caused different values to be generated on different
architectures. Additionally on big endian machines, the fate test
would output bytes in native order, which is different from the one
hardcoded in the test.

So, eradicate floating point numbers and use fixed point (32.32)
arithmetics everywhere, replacing constants with precomputed integer
values, and force the pixel format output to be the same in the fate
test.

Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>

1 files changed, 31 insertions, 27 deletions

diff --git a/libavcodec/pixlet.c b/libavcodec/pixlet.c
index 3b4ff42365..9f7d082fbe 100644
--- a/libavcodec/pixlet.c
+++ b/libavcodec/pixlet.c
@@ -39,8 +39,6 @@
 #define H 0
 #define V 1
 
-#define SQR(x) ((x) * (x))
-
 typedef struct SubBand {
     size_t width, height;
     size_t size;
@@ -59,7 +57,7 @@ typedef struct PixletContext {
 
     int16_t *filter[2];
     int16_t *prediction;
-    float scaling[4][2][NB_LEVELS];
+    int64_t scaling[4][2][NB_LEVELS];
     SubBand band[4][NB_LEVELS * 3 + 1];
 } PixletContext;
 
@@ -364,11 +362,11 @@ static void lowpass_prediction(int16_t *dst, int16_t *pred,
     }
 }
 
-static void filterfn(int16_t *dest, int16_t *tmp, size_t size, float SCALE)
+static void filterfn(int16_t *dest, int16_t *tmp, size_t size, int64_t scale)
 {
     int16_t *low, *high, *ll, *lh, *hl, *hh;
     int hsize, i, j;
-    float value;
+    int64_t value;
 
     hsize = size >> 1;
     low   = tmp + 4;
@@ -389,29 +387,29 @@ static void filterfn(int16_t *dest, int16_t *tmp, size_t size, float SCALE)
     }
 
     for (i = 0; i < hsize; i++) {
-        value = low [i + 1] * -0.07576144003329376f +
-                low [i + 0] *  0.8586296626673486f  +
-                low [i - 1] * -0.07576144003329376f +
-                high[i + 0] *  0.3535533905932737f  +
-                high[i - 1] *  0.3535533905932737f;
-        dest[i * 2] = av_clipf(value * SCALE, INT16_MIN, INT16_MAX);
+        value = (int64_t) low [i + 1] * -INT64_C(325392907)  +
+                (int64_t) low [i + 0] *  INT64_C(3687786320) +
+                (int64_t) low [i - 1] * -INT64_C(325392907)  +
+                (int64_t) high[i + 0] *  INT64_C(1518500249) +
+                (int64_t) high[i - 1] *  INT64_C(1518500249);
+        dest[i * 2] = av_clip_int16(((value >> 32) * scale) >> 32);
     }
 
     for (i = 0; i < hsize; i++) {
-        value = low [i + 2] * -0.01515228715813062f +
-                low [i + 1] *  0.3687056777514043f  +
-                low [i + 0] *  0.3687056777514043f  +
-                low [i - 1] * -0.01515228715813062f +
-                high[i + 1] *  0.07071067811865475f +
-                high[i + 0] * -0.8485281374238569f  +
-                high[i - 1] *  0.07071067811865475f;
-        dest[i * 2 + 1] = av_clipf(value * SCALE, INT16_MIN, INT16_MAX);
+        value = (int64_t) low [i + 2] * -INT64_C(65078576)   +
+                (int64_t) low [i + 1] *  INT64_C(1583578880) +
+                (int64_t) low [i + 0] *  INT64_C(1583578880) +
+                (int64_t) low [i - 1] * -INT64_C(65078576)   +
+                (int64_t) high[i + 1] *  INT64_C(303700064)  +
+                (int64_t) high[i + 0] * -INT64_C(3644400640) +
+                (int64_t) high[i - 1] *  INT64_C(303700064);
+        dest[i * 2 + 1] = av_clip_int16(((value >> 32) * scale) >> 32);
     }
 }
 
 static void reconstruction(AVCodecContext *avctx, int16_t *dest,
                            size_t width, size_t height, ptrdiff_t stride,
-                           float *scaling_h, float *scaling_v)
+                           int64_t *scaling_h, int64_t *scaling_v)
 {
     PixletContext *ctx = avctx->priv_data;
     unsigned scaled_width, scaled_height;
@@ -423,8 +421,8 @@ static void reconstruction(AVCodecContext *avctx, int16_t *dest,
     tmp           = ctx->filter[0];
 
     for (i = 0; i < NB_LEVELS; i++) {
-        float scale_v = scaling_v[i];
-        float scale_h = scaling_h[i];
+        int64_t scale_v = scaling_v[i];
+        int64_t scale_h = scaling_h[i];
         scaled_width  <<= 1;
         scaled_height <<= 1;
 
@@ -457,12 +455,18 @@ static void postprocess_luma(AVFrame *frame, size_t w, size_t h, int depth)
     uint16_t *dsty = (uint16_t *)frame->data[0];
     int16_t *srcy  = (int16_t *)frame->data[0];
     ptrdiff_t stridey = frame->linesize[0] / 2;
-    const float factor = 1.0f / ((1 << depth) - 1);
     int i, j;
 
     for (j = 0; j < h; j++) {
-        for (i = 0; i < w; i++)
-            dsty[i] = SQR(FFMAX(srcy[i], 0) * factor) * 65535;
+        for (i = 0; i < w; i++) {
+            if (srcy[i] <= 0)
+                dsty[i] = 0;
+            else if (srcy[i] > ((1 << depth) - 1))
+                dsty[i] = 65535;
+            else
+                dsty[i] = ((int64_t) srcy[i] * srcy[i] * 65535) /
+                          ((1 << depth) - 1) / ((1 << depth) - 1);
+        }
         dsty += stridey;
         srcy += stridey;
     }
@@ -508,8 +512,8 @@ static int decode_plane(AVCodecContext *avctx, int plane,
         if (!h || !v)
             return AVERROR_INVALIDDATA;
 
-        ctx->scaling[plane][H][i] = 1000000.0f / h;
-        ctx->scaling[plane][V][i] = 1000000.0f / v;
+        ctx->scaling[plane][H][i] = (1000000ULL << 32) / h;
+        ctx->scaling[plane][V][i] = (1000000ULL << 32) / v;
     }
 
     bytestream2_skip(&ctx->gb, 4);