Added testdata

testdata/.gitignore

@@ -0,0 +1 @@
+*.y4m

testdata/prepare.sh

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+#!/bin/bash
+
+pushd "${0%/*}" || exit
+
+# Samples taken from https://media.xiph.org/
+
+if [[ ! -f "sintel_trailer_2k_720p24.y4m" ]]; then
+  wget --show-progress -O "sintel_trailer_2k_720p24.y4m" https://media.xiph.org/video/derf/y4m/sintel_trailer_2k_720p24.y4m
+fi

testdata/testdata.go

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+package testdata
+
+import (
+	"os"
+	"path"
+	"runtime"
+)
+
+func init() {
+	_, filename, _, _ := runtime.Caller(0)
+	// The ".." may change depending on you folder structure
+	dir := path.Join(path.Dir(filename), "..")
+	err := os.Chdir(dir)
+	if err != nil {
+		panic(err)
+	}
+}
+
+const (
+	Y4M_Sintel_Trailer_720p24_YUV420_8bit = "testdata/sintel_trailer_2k_720p24.y4m"
+)