[FFmpeg-devel] [PATCH] lavf/id3v2enc: fix cover art display on some software

[Matthieu Bouron]

Adding an arbitrary amount of padding bytes at the end of the
ID3 metadata fixes cover art display for some software (iTunes,
Traktor, Serato, Torq).

For reference (ID3 metadata):

[ Apic frames ]                      → cover doesn't show up
[ Apic frames, Padding ]             → ok
[ Apic frames, ID3 frames ]          → ok
[ ID3 frames, Apic frames ]          → cover doesn't show up
[ ID3 frames, Apic frames, Padding ] → ok
---
 libavformat/id3v2enc.c  | 14 +++++++++++++-
 tests/ref/lavf-fate/mp3 |  4 ++--
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/libavformat/id3v2enc.c b/libavformat/id3v2enc.c
index 60ddbaa..d43d48f 100644
--- a/libavformat/id3v2enc.c
+++ b/libavformat/id3v2enc.c
@@ -28,6 +28,8 @@
 #include "avio.h"
 #include "id3v2.h"
 
+#define PADDING_BYTES 10
+
 static void id3v2_put_size(AVIOContext *pb, int size)
 {
     avio_w8(pb, size >> 21 & 0x7f);
@@ -319,7 +321,17 @@ int ff_id3v2_write_apic(AVFormatContext *s, ID3v2EncContext *id3, AVPacket *pkt)
 
 void ff_id3v2_finish(ID3v2EncContext *id3, AVIOContext *pb)
 {
-    int64_t cur_pos = avio_tell(pb);
+    int i;
+    int64_t cur_pos;
+
+    /* adding an arbitrary amount of padding bytes at the end of the
+     * ID3 metadata fixes cover art display for some software (iTunes,
+     * Traktor, Serato, Torq) */
+    for (i = 0; i < PADDING_BYTES; i++)
+        avio_w8(pb, 0);
+    id3->len += PADDING_BYTES;
+
+    cur_pos = avio_tell(pb);
     avio_seek(pb, id3->size_pos, SEEK_SET);
     id3v2_put_size(pb, id3->len);
     avio_seek(pb, cur_pos, SEEK_SET);
diff --git a/tests/ref/lavf-fate/mp3 b/tests/ref/lavf-fate/mp3
index 361314b..6f201e0 100644
--- a/tests/ref/lavf-fate/mp3
+++ b/tests/ref/lavf-fate/mp3
@@ -1,3 +1,3 @@
-7fcf80c2059b5c058a6cdd2e2f798b6c *./tests/data/lavf-fate/lavf.mp3
-96366 ./tests/data/lavf-fate/lavf.mp3
+6bdea919dc6856d76ef2553698e2b0d3 *./tests/data/lavf-fate/lavf.mp3
+96376 ./tests/data/lavf-fate/lavf.mp3
 ./tests/data/lavf-fate/lavf.mp3 CRC=0x6c9850fe
-- 
1.8.2.3