commit bb8e2a8594049067bc99f45fce9b74ea411bb791
author Wan-Teh Chang <wtc@google.com> Mon Jun 29 18:13:28 2020 -0700
committer Joe Drago <joedrago@gmail.com> Mon Jun 29 23:04:47 2020 -0700
tree 990e0b959677436345695b1f845dd954c445f767
parent 9c5f5653d1b08b1fd75b4af3fe8ed9c4a2ce0563

Remove checks for the "av01" brand

https://aomediacodec.github.io/av1-isobmff/ says a file conformant to
that spec shall have the 'av01' brand among the compatible brands array
of the FileTypeBox. The 'av01' brand (as opposed to the 'av01' image
item type) is not mentioned in the AVIF spec.

Therefore, 'av01' may be present in the compatible brands array of an
AVIF file, but it should not be the major brand of an AVIF file. In
addition, the presence of 'av01' in the compatible brands array does not
imply the file is AVIF.

Also use the || operator to connect the checks for the "avif" and "avis"
brands.

src/read.c

diff --git a/src/read.c b/src/read.c
index ce1c7cd..b112fc9 100644
--- a/src/read.c
+++ b/src/read.c
@@ -1872,25 +1872,11 @@
 
 static avifBool avifFileTypeIsCompatible(avifFileType * ftyp)
 {
-    avifBool avifCompatible = (memcmp(ftyp->majorBrand, "avif", 4) == 0);
-    if (!avifCompatible) {
-        avifCompatible = (memcmp(ftyp->majorBrand, "avis", 4) == 0);
-    }
-    if (!avifCompatible) {
-        avifCompatible = (memcmp(ftyp->majorBrand, "av01", 4) == 0);
-    }
+    avifBool avifCompatible = (memcmp(ftyp->majorBrand, "avif", 4) == 0 || memcmp(ftyp->majorBrand, "avis", 4) == 0);
     if (!avifCompatible) {
         for (int compatibleBrandIndex = 0; compatibleBrandIndex < ftyp->compatibleBrandsCount; ++compatibleBrandIndex) {
             uint8_t * compatibleBrand = &ftyp->compatibleBrands[4 * compatibleBrandIndex];
-            if (!memcmp(compatibleBrand, "avif", 4)) {
-                avifCompatible = AVIF_TRUE;
-                break;
-            }
-            if (!memcmp(compatibleBrand, "avis", 4)) {
-                avifCompatible = AVIF_TRUE;
-                break;
-            }
-            if (!memcmp(compatibleBrand, "av01", 4)) {
+            if (!memcmp(compatibleBrand, "avif", 4) || !memcmp(compatibleBrand, "avis", 4)) {
                 avifCompatible = AVIF_TRUE;
                 break;
             }