latmenc: fix muxing of byte-aligned DSE.

This will only work for DSEs that are first in a packet, but
that is enough to fix handling of the reference files in
fate-suite/aac (though most of them still have other issues).

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>

1 files changed, 14 insertions, 1 deletions

diff --git a/libavformat/latmenc.c b/libavformat/latmenc.c
index 3ee277d701..c296a1b116 100644
--- a/libavformat/latmenc.c
+++ b/libavformat/latmenc.c
@@ -166,8 +166,21 @@ static int latm_write_packet(AVFormatContext *s, AVPacket *pkt)
 
     /* The LATM payload is written unaligned */
 
+    i = 0;
+    if (pkt->size && (pkt->data[0] & 0xe1) == 0x81) {
+        // Convert byte-aligned DSE to non-aligned.
+        // Due to the input format encoding we know that
+        // it is naturally byte-aligned in the input stream,
+        // so there are no padding bits to account for.
+        // To avoid having to add padding bits and rearrange
+        // the whole stream we just remove the byte-align flag.
+        // This allows us to remux our FATE AAC samples into latm
+        // files that are still playable with minimal effort.
+        put_bits(&bs, 8, pkt->data[0] & 0xfe);
+        i++;
+    }
     /* PayloadMux() */
-    for (i = 0; i < pkt->size; i++)
+    for (; i < pkt->size; i++)
         put_bits(&bs, 8, pkt->data[i]);
 
     avpriv_align_put_bits(&bs);