libavformat/hlsenc.c: Populate OTI using AAC profile in write_codec_attr.

This patch populates the third entry for HLS codec attribute using the
AAC profile.

The HLS specifications[1] require this value to be the Object Type ID as
referred to in table 1.3 of ISO/IEC 14496-3:2009[2].

The numerical constants in the code refer to these OTIs minus one, as
documented in commit 372597e[3], confirmed by comparing the values in the
code with the values in the table mentioned above.

Links:
1: https://datatracker.ietf.org/doc/html/rfc6381#section-3.3
2: https://csclub.uwaterloo.ca/~ehashman/ISO14496-3-2009.pdf
3: 372597e538

Changes in this version:
- Default value set to "mp4a.40.2" when profile is unknown for backward
  compatibility.

Signed-off-by: Steven Liu <liuqi05@kuaishou.com>
(cherry picked from commit 797f0b27c1)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/hlsenc.c

@@ -411,8 +411,11 @@ static void write_codec_attr(AVStream *st, VariantStream *vs)
     } else if (st->codecpar->codec_id == AV_CODEC_ID_MP3) {
         snprintf(attr, sizeof(attr), "mp4a.40.34");
     } else if (st->codecpar->codec_id == AV_CODEC_ID_AAC) {
-        /* TODO : For HE-AAC, HE-AACv2, the last digit needs to be set to 5 and 29 respectively */
-        snprintf(attr, sizeof(attr), "mp4a.40.2");
+        if (st->codecpar->profile != FF_PROFILE_UNKNOWN)
+            snprintf(attr, sizeof(attr), "mp4a.40.%d", st->codecpar->profile+1);
+        else
+            // This is for backward compatibility with the previous implementation.
+            snprintf(attr, sizeof(attr), "mp4a.40.2");
     } else if (st->codecpar->codec_id == AV_CODEC_ID_AC3) {
         snprintf(attr, sizeof(attr), "ac-3");
     } else if (st->codecpar->codec_id == AV_CODEC_ID_EAC3) {