opus: Try to decode invalid image tags manually. Closes: #1387

opus_picture_tag_parse() will return an error on picture metadata with
non-zero width/height but 0 for depth. Unfortunately a lot of programs
write such tags because they were generally accepted for Ogg container
files containing Vorbis audio, and are strictly advisory (they don't
affect image decoding). Other programs (e.g. VLC) seem to also decode
Opus picture tags manually as well.

Co-authored-by: Thomas Lange <[email protected]>

Author: bkoropoff

src/opus/Makefile

@@ -10,5 +10,5 @@ plugindir := ${plugindir}/${INPUT_PLUGIN_DIR}
 LD = ${CXX}
 
 CFLAGS += ${PLUGIN_CFLAGS}
-CPPFLAGS += ${PLUGIN_CPPFLAGS} ${OPUS_CFLAGS} -I../..
-LIBS += ${OPUS_LIBS}
+CPPFLAGS += ${PLUGIN_CPPFLAGS} ${OPUS_CFLAGS} ${GLIB_CFLAGS} -I../..
+LIBS += ${OPUS_LIBS} ${GLIB_LIBS}

src/opus/meson.build

@@ -5,7 +5,7 @@ have_opus = opusfile_dep.found()
 if have_opus
   shared_module('opus',
     'opus.cc',
-    dependencies: [audacious_dep, opusfile_dep],
+    dependencies: [audacious_dep, glib_dep, opusfile_dep],
     name_prefix: '',
     include_directories: [src_inc],
     install: true,

src/opus/opus.cc

@@ -20,8 +20,11 @@
 #include <cstdlib>
 #include <cstring>
 
+#include <glib.h>
 #include <opus/opusfile.h>
 
+#define AUD_GLIB_INTEGRATION
+#define WANT_AUD_BSWAP
 #define WANT_VFS_STDIO_COMPAT
 #include <libaudcore/audstrings.h>
 #include <libaudcore/i18n.h>
@@ -128,6 +131,35 @@ static void read_tags(const OpusTags * tags, Tuple & tuple)
         tuple.set_int(Tuple::Year, std::atoi(date));
 }
 
+/*
+ * Adopted from Ogg Vorbis decoder plugin
+ * Used as less strict fallback if opusfile rejects an image tag
+ */
+static bool parse_vorbis_image(Index<char> & data, const char * image)
+{
+    unsigned mime_length, desc_length, length;
+    size_t data_length;
+
+    CharPtr img_data((char *)g_base64_decode(image, &data_length));
+    if (!img_data || data_length < 8)
+        return false;
+
+    mime_length = FROM_BE32(*(uint32_t *)(img_data + 4));
+    if (data_length < 8 + mime_length + 4)
+        return false;
+
+    desc_length = FROM_BE32(*(uint32_t *)(img_data + 8 + mime_length));
+    if (data_length < 8 + mime_length + 4 + desc_length + 20)
+        return false;
+
+    length = FROM_BE32(*(uint32_t *)(img_data + 8 + mime_length + 4 + desc_length + 16));
+    if (data_length < 8 + mime_length + 4 + desc_length + 20 + length)
+        return false;
+
+    data.insert(img_data + 8 + mime_length + 4 + desc_length + 20, 0, length);
+    return true;
+}
+
 static Index<char> read_image_from_tags(const OpusTags * tags,
                                         const char * filename)
 {
@@ -140,7 +172,8 @@ static Index<char> read_image_from_tags(const OpusTags * tags,
     OpusPictureTag picture_tag;
     if (opus_picture_tag_parse(&picture_tag, image) < 0)
     {
-        AUDERR("Error parsing METADATA_BLOCK_PICTURE in %s.\n", filename);
+        if (!parse_vorbis_image(data, image))
+            AUDERR("Error parsing METADATA_BLOCK_PICTURE in %s.\n", filename);
         return data;
     }