Use 64-byte alignment for aligned image memory.

FFmpeg uses this values if AVX512 is available, and with only
32-byte alignment I am seeing strange scaling effects whereby
crop_scale_window_test7 gives black bars down the right side of
cropped images (when run on an i7 7700).

diff --git a/src/lib/image.cc b/src/lib/image.cc
index 1439d9f7f964228385ba20e28c0bbb8ba85082c5..61945e1c99dce64d6cf3f7570a8ecf21a93adc9f 100644 (file)
--- a/src/lib/image.cc
+++ b/src/lib/image.cc
@@ -55,6 +55,11 @@ using std::runtime_error;
 using boost::shared_ptr;
 using dcp::Size;
 
+
+/** The memory alignment, in bytes, used for each row of an image if aligment is requested */
+#define ALIGNMENT 64
+
+
 int
 Image::vertical_factor (int n) const
 {
@@ -830,7 +835,7 @@ Image::bytes_per_pixel (int c) const
  *
  *  @param p Pixel format.
  *  @param s Size in pixels.
- *  @param aligned true to make each row of this image aligned to a 32-byte boundary.
+ *  @param aligned true to make each row of this image aligned to a ALIGNMENT-byte boundary.
  */
 Image::Image (AVPixelFormat p, dcp::Size s, bool aligned)
        : _size (s)
@@ -854,7 +859,7 @@ Image::allocate ()
 
        for (int i = 0; i < planes(); ++i) {
                _line_size[i] = ceil (_size.width * bytes_per_pixel(i));
-               _stride[i] = stride_round_up (i, _line_size, _aligned ? 32 : 1);
+               _stride[i] = stride_round_up (i, _line_size, _aligned ? ALIGNMENT : 1);
 
                /* The assembler function ff_rgb24ToY_avx (in libswscale/x86/input.asm)
                   uses a 16-byte fetch to read three bytes (R/G/B) of image data.
@@ -867,7 +872,7 @@ Image::allocate ()
 
                   Further to the above, valgrind is now telling me that ff_rgb24ToY_ssse3
                   over-reads by more then _avx.  I can't follow the code to work out how much,
-                  so I'll just over-allocate by 32 bytes and have done with it.  Empirical
+                  so I'll just over-allocate by ALIGNMENT bytes and have done with it.  Empirical
                   testing suggests that it works.
 
                   In addition to these concerns, we may read/write as much as a whole extra line
@@ -893,12 +898,12 @@ Image::allocate ()
                   |XXXwrittenXXX|<------line-size------------->|XXXwrittenXXXXXXwrittenXXX
                                                                               ^^^^ out of bounds
                */
-               _data[i] = (uint8_t *) wrapped_av_malloc (_stride[i] * (sample_size(i).height + 1) + 32);
+               _data[i] = (uint8_t *) wrapped_av_malloc (_stride[i] * (sample_size(i).height + 1) + ALIGNMENT);
 #if HAVE_VALGRIND_MEMCHECK_H
                /* The data between the end of the line size and the stride is undefined but processed by
                   libswscale, causing lots of valgrind errors.  Mark it all defined to quell these errors.
                */
-               VALGRIND_MAKE_MEM_DEFINED (_data[i], _stride[i] * (sample_size(i).height + 1) + 32);
+               VALGRIND_MAKE_MEM_DEFINED (_data[i], _stride[i] * (sample_size(i).height + 1) + ALIGNMENT);
 #endif
        }
 }

diff --git a/test/image_test.cc b/test/image_test.cc
index 8579785a74aeebe264c63978280d2136d1b66ba9..3c89d5da7b2aa2b874aa39c60aea918f128cb37e 100644 (file)
--- a/test/image_test.cc
+++ b/test/image_test.cc
@@ -39,8 +39,8 @@ BOOST_AUTO_TEST_CASE (aligned_image_test)
 {
        Image* s = new Image (AV_PIX_FMT_RGB24, dcp::Size (50, 50), true);
        BOOST_CHECK_EQUAL (s->planes(), 1);
-       /* 160 is 150 aligned to the nearest 32 bytes */
-       BOOST_CHECK_EQUAL (s->stride()[0], 160);
+       /* 192 is 150 aligned to the nearest 64 bytes */
+       BOOST_CHECK_EQUAL (s->stride()[0], 192);
        BOOST_CHECK_EQUAL (s->line_size()[0], 150);
        BOOST_CHECK (s->data()[0]);
        BOOST_CHECK (!s->data()[1]);
@@ -50,7 +50,7 @@ BOOST_AUTO_TEST_CASE (aligned_image_test)
        /* copy constructor */
        Image* t = new Image (*s);
        BOOST_CHECK_EQUAL (t->planes(), 1);
-       BOOST_CHECK_EQUAL (t->stride()[0], 160);
+       BOOST_CHECK_EQUAL (t->stride()[0], 192);
        BOOST_CHECK_EQUAL (t->line_size()[0], 150);
        BOOST_CHECK (t->data()[0]);
        BOOST_CHECK (!t->data()[1]);
@@ -67,7 +67,7 @@ BOOST_AUTO_TEST_CASE (aligned_image_test)
        Image* u = new Image (AV_PIX_FMT_YUV422P, dcp::Size (150, 150), false);
        *u = *s;
        BOOST_CHECK_EQUAL (u->planes(), 1);
-       BOOST_CHECK_EQUAL (u->stride()[0], 160);
+       BOOST_CHECK_EQUAL (u->stride()[0], 192);
        BOOST_CHECK_EQUAL (u->line_size()[0], 150);
        BOOST_CHECK (u->data()[0]);
        BOOST_CHECK (!u->data()[1]);