[FFmpeg-devel] avformat/hlsplaylist: Support FRAME-RATE attribute

[Arzet Ro]

https://datatracker.ietf.org/doc/html/rfc8216#page-31

Signed-off-by: Arzet Ro <arzeth0 at gmail.com>
---
 libavformat/hlsplaylist.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/libavformat/hlsplaylist.c b/libavformat/hlsplaylist.c
index 0e1dcc087f..c3ec86f2ab 100644
--- a/libavformat/hlsplaylist.c
+++ b/libavformat/hlsplaylist.c
@@ -81,9 +81,32 @@ void ff_hls_write_stream_info(AVStream *st, AVIOContext *out, int bandwidth,
     }
 
     avio_printf(out, "#EXT-X-STREAM-INF:BANDWIDTH=%d", bandwidth);
-    if (st && st->codecpar->width > 0 && st->codecpar->height > 0)
+    if (st && st->codecpar->width > 0 && st->codecpar->height > 0) {
         avio_printf(out, ",RESOLUTION=%dx%d", st->codecpar->width,
                 st->codecpar->height);
+        if (st->avg_frame_rate.num > 0) {
+            // In an ideal world #EXT-X-VERSION should be >=7 if we want FRAME-RATE
+            // according to
+            // https://developer.apple.com/documentation/http_live_streaming/about_the_ext-x-version_tag
+            // But we can ignore that because:
+            // https://datatracker.ietf.org/doc/html/rfc8216#section-6.3.1
+            // "To support forward compatibility, when parsing Playlists,
+            // clients MUST ignore any attribute/value pair
+            // with an unrecognized AttributeName.".
+
+
+            // https://datatracker.ietf.org/doc/html/rfc8216#page-31
+            // "The value is a decimal-floating-point describing the maximum frame
+            // rate for all the video in the Variant Stream, rounded to three
+            // decimal places."
+
+            // Also, iOS and tvOS refuse to play the content if VIDEO-RANGE is
+            // present but FRAME-RATE is missing.
+            // Although at this moment
+            // VIDEO-RANGE attribute is not implemented in FFmpeg.
+            avio_printf(out, ",FRAME-RATE=%.3f", av_q2d(st->avg_frame_rate));
+        }
+    }
     if (codecs && codecs[0])
         avio_printf(out, ",CODECS=\"%s\"", codecs);
     if (agroup && agroup[0])
-- 
2.32.0