[FFmpeg-devel] [PATCH v2] libavformat/hlsenc.c: Populate OTI using AAC profile in write_codec_attr.

[Romain Beauxis]

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: https://github.com/FFmpeg/FFmpeg/commit/372597e5381c097455a7b73849254d56083eb056

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

---
 libavformat/hlsenc.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/libavformat/hlsenc.c b/libavformat/hlsenc.c
index 7049956dd7..55123d2297 100644
--- a/libavformat/hlsenc.c
+++ b/libavformat/hlsenc.c
@@ -418,8 +418,11 @@ 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 != AV_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) {
-- 
2.39.3 (Apple Git-145)