[FFmpeg-devel] [PATCH 3/3] avformat/hls: add http_keepalive option

[Aman Gupta]

From: Aman Gupta <aman at tmm1.net>

This teaches the HLS demuxer to use the HTTP protocols
multiple_requests=1 option, to take advantage of "Connection:
Keep-Alive" when downloading playlists and segments from the HLS server.

With the new option, you can avoid TCP connection and TLS negotiation
overhead, which is particularly beneficial when streaming via a
high-latency internet connection.
---
 libavformat/hls.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 47 insertions(+), 4 deletions(-)

diff --git a/libavformat/hls.c b/libavformat/hls.c
index 786934af03..bf90582755 100644
--- a/libavformat/hls.c
+++ b/libavformat/hls.c
@@ -26,6 +26,7 @@
  * http://tools.ietf.org/html/draft-pantos-http-live-streaming
  */
 
+#include "libavformat/http.h"
 #include "libavutil/avstring.h"
 #include "libavutil/avassert.h"
 #include "libavutil/intreadwrite.h"
@@ -94,6 +95,7 @@ struct playlist {
     AVIOContext pb;
     uint8_t* read_buffer;
     AVIOContext *input;
+    int input_done;
     AVFormatContext *parent;
     int index;
     AVFormatContext *ctx;
@@ -206,6 +208,8 @@ typedef struct HLSContext {
     int strict_std_compliance;
     char *allowed_extensions;
     int max_reload;
+    int http_keepalive;
+    AVIOContext *playlist_pb;
 } HLSContext;
 
 static int read_chomp_line(AVIOContext *s, char *buf, int maxlen)
@@ -640,7 +644,17 @@ static int open_url(AVFormatContext *s, AVIOContext **pb, const char *url,
     else if (strcmp(proto_name, "file") || !strncmp(url, "file,", 5))
         return AVERROR_INVALIDDATA;
 
-    ret = s->io_open(s, pb, url, AVIO_FLAG_READ, &tmp);
+    if (c->http_keepalive && *pb && av_strstart(proto_name, "http", NULL)) {
+        URLContext *uc = (URLContext *)av_opt_child_next(*pb, NULL);
+        (*pb)->eof_reached = 0;
+        ret = ff_http_do_new_request(uc, url);
+        if (ret < 0) {
+            ff_format_io_close(c->ctx, pb);
+            ret = s->io_open(s, pb, url, AVIO_FLAG_READ, &tmp);
+        }
+    } else {
+        ret = s->io_open(s, pb, url, AVIO_FLAG_READ, &tmp);
+    }
     if (ret >= 0) {
         // update cookies on http response with setcookies.
         char *new_cookies = NULL;
@@ -683,10 +697,20 @@ static int parse_playlist(HLSContext *c, const char *url,
     char tmp_str[MAX_URL_SIZE];
     struct segment *cur_init_section = NULL;
 
+    if (!in && c->http_keepalive && c->playlist_pb) {
+        in = c->playlist_pb;
+        URLContext *uc = (URLContext *)av_opt_child_next(in, NULL);
+        in->eof_reached = 0;
+        ret = ff_http_do_new_request(uc, url);
+        if (ret < 0) {
+            ff_format_io_close(c->ctx, &c->playlist_pb);
+            in = NULL;
+        }
+    }
+
     if (!in) {
 #if 1
         AVDictionary *opts = NULL;
-        close_in = 1;
         /* Some HLS servers don't like being sent the range header */
         av_dict_set(&opts, "seekable", "0", 0);
 
@@ -696,10 +720,18 @@ static int parse_playlist(HLSContext *c, const char *url,
         av_dict_set(&opts, "headers", c->headers, 0);
         av_dict_set(&opts, "http_proxy", c->http_proxy, 0);
 
+        if (c->http_keepalive)
+            av_dict_set(&opts, "multiple_requests", "1", 0);
+
         ret = c->ctx->io_open(c->ctx, &in, url, AVIO_FLAG_READ, &opts);
         av_dict_free(&opts);
         if (ret < 0)
             return ret;
+
+        if (c->http_keepalive)
+            c->playlist_pb = in;
+        else
+            close_in = 1;
 #else
         ret = open_in(c, &in, url);
         if (ret < 0)
@@ -1111,6 +1143,9 @@ static int open_input(HLSContext *c, struct playlist *pls, struct segment *seg)
     av_dict_set(&opts, "http_proxy", c->http_proxy, 0);
     av_dict_set(&opts, "seekable", "0", 0);
 
+    if (c->http_keepalive)
+        av_dict_set(&opts, "multiple_requests", "1", 0);
+
     if (seg->size >= 0) {
         /* try to restrict the HTTP request to the part we want
          * (if this is in fact a HTTP request) */
@@ -1270,7 +1305,7 @@ restart:
     if (!v->needed)
         return AVERROR_EOF;
 
-    if (!v->input) {
+    if (!v->input || (c->http_keepalive && v->input_done)) {
         int64_t reload_interval;
         struct segment *seg;
 
@@ -1329,6 +1364,7 @@ reload:
             goto reload;
         }
 
+        v->input_done = 0;
         seg = current_segment(v);
 
         /* load/update Media Initialization Section, if any */
@@ -1366,7 +1402,11 @@ reload:
 
         return ret;
     }
-    ff_format_io_close(v->parent, &v->input);
+    if (c->http_keepalive) {
+        v->input_done = 1;
+    } else {
+        ff_format_io_close(v->parent, &v->input);
+    }
     v->cur_seq_no++;
 
     c->cur_seq_no = v->cur_seq_no;
@@ -1627,6 +1667,7 @@ static int hls_close(AVFormatContext *s)
     free_rendition_list(c);
 
     av_dict_free(&c->avio_opts);
+    ff_format_io_close(c->ctx, &c->playlist_pb);
 
     return 0;
 }
@@ -2157,6 +2198,8 @@ static const AVOption hls_options[] = {
         INT_MIN, INT_MAX, FLAGS},
     {"max_reload", "Maximum number of times a insufficient list is attempted to be reloaded",
         OFFSET(max_reload), AV_OPT_TYPE_INT, {.i64 = 1000}, 0, INT_MAX, FLAGS},
+    {"http_keepalive", "re-use http connections when reloading playlists and fetching new segments",
+        OFFSET(http_keepalive), AV_OPT_TYPE_BOOL, {.i64 = 0}, INT_MIN, 1, FLAGS},
     {NULL}
 };
 
-- 
2.13.5 (Apple Git-94)