avformat/hlsenc: add var_stream_map DEFAULT field status parameter

use a:0,agroup:aud_low,default:Yes a:1,agroup:aud_low,
    a:2,agroup:aud_high,default:Yes a:3, agroup:aud_high,
    v:0,agroup:aud_low v:1,agroup:aud_high
    create master m3u8 list.

result:
EXTM3U
EXT-X-VERSION:3
EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="group_aud_low",NAME="audio_0",DEFAULT=YES,URI="out_0.m3u8"
EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="group_aud_low",NAME="audio_1",DEFAULT=NO,URI="out_1.m3u8"
EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="group_aud_high",NAME="audio_2",DEFAULT=YES,URI="out_2.m3u8"
EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="group_aud_high",NAME="audio_3",DEFAULT=NO,URI="out_3.m3u8"
EXT-X-STREAM-INF:BANDWIDTH=1170400,RESOLUTION=640x480,CODECS="avc1.64001e,mp4a.40.2",AUDIO="group_aud_low"
out_4.m3u8
EXT-X-STREAM-INF:BANDWIDTH=3440800,RESOLUTION=640x480,CODECS="avc1.64001e,mp4a.40.2",AUDIO="group_aud_high"
out_5.m3u8

Signed-off-by: Steven Liu <lq@chinaffmpeg.org>

doc/muxers.texi

@@ -967,6 +967,21 @@ and they are mapped to the two video only variant streams with audio group names
 
 By default, a single hls variant containing all the encoded streams is created.
 
+@example
+ffmpeg -re -i in.ts -b:a:0 32k -b:a:1 64k -b:v:0 1000k \
+  -map 0:a -map 0:a -map 0:v -f hls \
+  -var_stream_map "a:0,agroup:aud_low,default:yes a:1,agroup:aud_low v:0,agroup:aud_low" \
+  -master_pl_name master.m3u8 \
+  http://example.com/live/out_%v.m3u8
+@end example
+This example creates two audio only and one video only variant streams. In
+addition to the #EXT-X-STREAM-INF tag for each variant stream in the master
+playlist, #EXT-X-MEDIA tag is also added for the two audio only variant streams
+and they are mapped to the one video only variant streams with audio group name
+'aud_low', and the audio group have default stat is NO or YES.
+
+By default, a single hls variant containing all the encoded streams is created.
+
 @item cc_stream_map
 Map string which specifies different closed captions groups and their
 attributes. The closed captions stream groups are separated by space.

libavformat/hlsenc.c

@@ -153,6 +153,7 @@ typedef struct VariantStream {
     CodecAttributeStatus attr_status;
     unsigned int nb_streams;
     int m3u8_created; /* status of media play-list creation */
+    int is_default; /* default status of audio group */
     char *agroup; /* audio group name */
     char *ccgroup; /* closed caption group name */
     char *baseurl;
@@ -228,6 +229,8 @@ typedef struct HLSContext {
     AVIOContext *sub_m3u8_out;
     int64_t timeout;
     int ignore_io_errors;
+    int has_default_key; /* has DEFAULT field of var_stream_map */
+    int has_video_m3u8; /* has video stream m3u8 list */
 } HLSContext;
 
 static int hlsenc_io_open(AVFormatContext *s, AVIOContext **pb, char *filename,
@@ -1258,7 +1261,7 @@ static int create_master_playlist(AVFormatContext *s,
             goto fail;
         }
 
-        ff_hls_write_audio_rendition(hls->m3u8_out, vs->agroup, m3u8_rel_name, i, 1);
+        ff_hls_write_audio_rendition(hls->m3u8_out, vs->agroup, m3u8_rel_name, i, hls->has_default_key ? vs->is_default : 1);
 
         av_freep(&m3u8_rel_name);
     }
@@ -1336,8 +1339,15 @@ static int create_master_playlist(AVFormatContext *s,
                         vs->ccgroup);
         }
 
+        if (!hls->has_default_key || !hls->has_video_m3u8) {
             ff_hls_write_stream_info(vid_st, hls->m3u8_out, bandwidth, m3u8_rel_name,
                     aud_st ? vs->agroup : NULL, vs->codec_attr, ccgroup);
+        } else {
+            if (vid_st) {
+                ff_hls_write_stream_info(vid_st, hls->m3u8_out, bandwidth, m3u8_rel_name,
+                                         aud_st ? vs->agroup : NULL, vs->codec_attr, ccgroup);
+            }
+        }
 
         av_freep(&m3u8_rel_name);
     }
@@ -1819,7 +1829,7 @@ static int parse_variant_stream_mapstring(AVFormatContext *s)
     /**
      * Expected format for var_stream_map string is as below:
      * "a:0,v:0 a:1,v:1"
-     * "a:0,agroup:a0 a:1,agroup:a1 v:0,agroup:a0  v:1,agroup:a1"
+     * "a:0,agroup:a0,default:1 a:1,agroup:a1,defalut:0 v:0,agroup:a0  v:1,agroup:a1"
      * This string specifies how to group the audio, video and subtitle streams
      * into different variant streams. The variant stream groups are separated
      * by space.
@@ -1850,6 +1860,7 @@ static int parse_variant_stream_mapstring(AVFormatContext *s)
         if (nb_varstreams < hls->nb_varstreams) {
             vs = &(hls->var_streams[nb_varstreams]);
             vs->var_stream_idx = nb_varstreams;
+            vs->is_default = 0;
             nb_varstreams++;
         } else
             return AVERROR(EINVAL);
@@ -1869,7 +1880,12 @@ static int parse_variant_stream_mapstring(AVFormatContext *s)
         while (keyval = av_strtok(varstr, ",", &saveptr2)) {
             varstr = NULL;
 
-            if (av_strstart(keyval, "agroup:", &val)) {
+            if (av_strstart(keyval, "default:", &val)) {
+                vs->is_default = (!av_strncasecmp(val, "YES", strlen("YES")) ||
+                                  (!av_strncasecmp(val, "1", strlen("1"))));
+                hls->has_default_key = 1;
+                continue;
+            } else if (av_strstart(keyval, "agroup:", &val)) {
                 vs->agroup = av_strdup(val);
                 if (!vs->agroup)
                     return AVERROR(ENOMEM);
@@ -1881,6 +1897,7 @@ static int parse_variant_stream_mapstring(AVFormatContext *s)
                 continue;
             } else if (av_strstart(keyval, "v:", &val)) {
                 codec_type = AVMEDIA_TYPE_VIDEO;
+                hls->has_video_m3u8 = 1;
             } else if (av_strstart(keyval, "a:", &val)) {
                 codec_type = AVMEDIA_TYPE_AUDIO;
             } else if (av_strstart(keyval, "s:", &val)) {
@@ -2519,6 +2536,8 @@ static int hls_init(AVFormatContext *s)
     int vtt_basename_size = 0;
     int fmp4_init_filename_len = strlen(hls->fmp4_init_filename) + 1;
 
+    hls->has_default_key = 0;
+    hls->has_video_m3u8 = 0;
     ret = update_variant_stream_info(s);
     if (ret < 0) {
         av_log(s, AV_LOG_ERROR, "Variant stream info update failed with status %x\n",