hlsenc: Add parameter -hls_allow_cache

The -hls_allow_cache parameter enables explicitly setting the
EXT-X-ALLOW-CACHE tag in the manifest file. That tag indicates
whether the client MAY or MUST NOT cache downloaded media
segments for later replay.

Valid values are 1 (=YES) or 0 (=NO) and the EXT-X-ALLOW-CACHE
will not show in the manifest for other values (or if
-hls_allow_cache is not used.
Signed-off-by: Martin Storsjö <martin@martin.st>

doc/muxers.texi

@@ -117,6 +117,8 @@ Start the sequence from @var{number}.
 @item -hls_base_url @var{baseurl}
 Append @var{baseurl} to every entry in the playlist.
 Useful to generate playlists with absolute paths.
+@item -hls_allow_cache @var{allowcache}
+Explicitly set whether the client MAY (1) or MUST NOT (0) cache media segments
 @end table
 
 @anchor{image2}

libavformat/hlsenc.c

@@ -47,6 +47,7 @@ typedef struct HLSContext {
     float time;            // Set by a private option.
     int  size;             // Set by a private option.
     int  wrap;             // Set by a private option.
+    int  allowcache;
     int64_t recording_time;
     int has_video;
     int64_t start_pts;
@@ -145,6 +146,9 @@ static int hls_window(AVFormatContext *s, int last)
 
     avio_printf(hls->pb, "#EXTM3U\n");
     avio_printf(hls->pb, "#EXT-X-VERSION:3\n");
+    if (hls->allowcache == 0 || hls->allowcache == 1) {
+        avio_printf(hls->pb, "#EXT-X-ALLOW-CACHE:%s\n", hls->allowcache == 0 ? "NO" : "YES");
+    }
     avio_printf(hls->pb, "#EXT-X-TARGETDURATION:%d\n", target_duration);
     avio_printf(hls->pb, "#EXT-X-MEDIA-SEQUENCE:%"PRId64"\n", sequence);
 
@@ -325,6 +329,7 @@ static const AVOption options[] = {
     {"hls_time",      "segment length in seconds",               OFFSET(time),    AV_OPT_TYPE_FLOAT,  {.dbl = 2},     0, FLT_MAX, E},
     {"hls_list_size", "maximum number of playlist entries",      OFFSET(size),    AV_OPT_TYPE_INT,    {.i64 = 5},     0, INT_MAX, E},
     {"hls_wrap",      "number after which the index wraps",      OFFSET(wrap),    AV_OPT_TYPE_INT,    {.i64 = 0},     0, INT_MAX, E},
+    {"hls_allow_cache", "explicitly set whether the client MAY (1) or MUST NOT (0) cache media segments", OFFSET(allowcache), AV_OPT_TYPE_INT, {.i64 = -1}, INT_MIN, INT_MAX, E},
     {"hls_base_url",  "url to prepend to each playlist entry",   OFFSET(baseurl), AV_OPT_TYPE_STRING, {.str = NULL},  0, 0,       E},
     { NULL },
 };

libavformat/version.h

@@ -31,7 +31,7 @@
 
 #define LIBAVFORMAT_VERSION_MAJOR 56
 #define LIBAVFORMAT_VERSION_MINOR  5
-#define LIBAVFORMAT_VERSION_MICRO  0
+#define LIBAVFORMAT_VERSION_MICRO  1
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
                                                LIBAVFORMAT_VERSION_MINOR, \