From d50470bc7db942105c3bd774ea08a836b842d58c Mon Sep 17 00:00:00 2001
From: Roman Artiukhin <bahusdrive@gmail.com>
Date: Wed, 3 Jan 2024 17:30:18 +0200
Subject: Codecs: aac: Improve ADTS stream detection

Captured ADTS streams might start from some garbage data from previous frame. We should check for sync errors even for first frame.

Change-Id: I70171298b79713aeedf9fa2e6098a03063487649
---
 lib/rbcodec/metadata/aac.c | 50 +++++++++++++++++++++++++++++-----------------
 1 file changed, 32 insertions(+), 18 deletions(-)

(limited to 'lib/rbcodec/metadata/aac.c')

diff --git a/lib/rbcodec/metadata/aac.c b/lib/rbcodec/metadata/aac.c
index 372bab716e..c5467f0422 100644
--- a/lib/rbcodec/metadata/aac.c
+++ b/lib/rbcodec/metadata/aac.c
@@ -47,6 +47,24 @@ static bool check_adts_syncword(int fd)
     return (syncword & 0xFFF6) == 0xFFF0;
 }
 
+static bool find_adts_keyword(int fd, struct mp3entry *entry)
+{
+    /* logic is copied from adts_fixed_header libfaad/syntax.c:
+     * try to recover from sync errors */
+    for (int i = 0; i < 768; ++i)
+    {
+        if (-1 == lseek(fd, entry->first_frame_offset + i, SEEK_SET))
+            return false;
+
+        if (check_adts_syncword(fd))
+        {
+            return true;
+        }
+    }
+
+    return false;
+}
+
 bool get_aac_metadata(int fd, struct mp3entry *entry)
 {
     unsigned char buf[5];
@@ -65,8 +83,21 @@ bool get_aac_metadata(int fd, struct mp3entry *entry)
 
     if (-1 == lseek(fd, entry->first_frame_offset, SEEK_SET))
         return false;
+    if (read(fd, buf, 5) != 5)
+        return false;
+    if (!memcmp(buf, "ADIF", 4))
+    {
+        if (-1 == lseek(fd, (buf[4] & 0x80) ? (entry->first_frame_offset + 9) : entry->first_frame_offset, SEEK_SET))
+            return false;
 
-    if (check_adts_syncword(fd))
+        uint32_t bitrate;
+        read_uint32be(fd, &bitrate);
+        entry->vbr = (bitrate & 0x10000000) != 0;
+        entry->bitrate = ((bitrate & 0xFFFFFE0) + 16000) / 32000;
+        read_uint32be(fd, (uint32_t*)(&(entry->frequency)));
+        entry->frequency = sample_rates[(entry->frequency >> (entry->vbr ? 23 : 3)) & 0x0F];
+    }
+    else if (find_adts_keyword(fd, entry))
     {
         int frames;
         int stat_length;
@@ -101,23 +132,6 @@ bool get_aac_metadata(int fd, struct mp3entry *entry)
         }
 #endif
     }
-    else
-    {
-        uint32_t bitrate;
-        if (-1 == lseek(fd, entry->first_frame_offset, SEEK_SET))
-            return false;
-        if (read(fd, buf, 5) != 5)
-            return false;
-        if (memcmp(buf, "ADIF", 4))
-            return false;
-        if (-1 == lseek(fd, (buf[4] & 0x80) ? (entry->first_frame_offset + 9) : entry->first_frame_offset, SEEK_SET))
-            return false;
-        read_uint32be(fd, &bitrate);
-        entry->vbr = (bitrate & 0x10000000) != 0;
-        entry->bitrate = ((bitrate & 0xFFFFFE0) + 16000) / 32000;
-        read_uint32be(fd, (uint32_t*)(&(entry->frequency)));
-        entry->frequency = sample_rates[(entry->frequency >> (entry->vbr ? 23 : 3)) & 0x0F];
-    }
     entry->length = (unsigned long)((entry->filesize * 8LL + (entry->bitrate >> 1)) / entry->bitrate);
 
     return true;
-- 
cgit v1.2.3