lavf/segment: add segment_list_entry_prefix option

This option allows to add a prefix to the segment list entry filenames.

Also set by default the list entry filenames to the corresponding
segment basename, consistent with the HLS muxer.

Based on an idea by Steven Liu <lingjiujianke@gmail.com>.

doc/muxers.texi

@@ -674,7 +674,9 @@ The segment muxer works best with a single constant frame rate video.
 
 Optionally it can generate a list of the created segments, by setting
 the option @var{segment_list}. The list type is specified by the
-@var{segment_list_type} option.
+@var{segment_list_type} option. The entry filenames in the segment
+list are set by default to the basename of the corresponding segment
+files.
 
 The segment muxer supports the following options:
 
@@ -711,6 +713,10 @@ Update the list file so that it contains at most the last @var{size}
 segments. If 0 the list file will contain all the segments. Default
 value is 0.
 
+@item segment_list_entry_prefix @var{prefix}
+Set @var{prefix} to prepend to the name of each entry filename. By
+default no prefix is applied.
+
 @item segment_list_type @var{type}
 Specify the format for the segment list file.
 

libavformat/segment.c

@@ -44,7 +44,7 @@ typedef struct SegmentListEntry {
     double start_time, end_time;
     int64_t start_pts;
     int64_t offset_pts;
-    char filename[1024];
+    char *filename;
     struct SegmentListEntry *next;
 } SegmentListEntry;
 
@@ -72,6 +72,7 @@ typedef struct {
     char *list;            ///< filename for the segment list file
     int   list_flags;      ///< flags affecting list generation
     int   list_size;       ///< number of entries for the segment list file
+    char *list_entry_prefix; ///< prefix to add to list entry filenames
     ListType list_type;    ///< set the list type
     AVIOContext *list_pb;  ///< list file put-byte context
     char *time_str;        ///< segment duration specification string
@@ -158,6 +159,7 @@ static int set_segment_filename(AVFormatContext *s)
 {
     SegmentContext *seg = s->priv_data;
     AVFormatContext *oc = seg->avf;
+    size_t size;
 
     if (seg->segment_idx_wrap)
         seg->segment_idx %= seg->segment_idx_wrap;
@@ -166,7 +168,19 @@ static int set_segment_filename(AVFormatContext *s)
         av_log(oc, AV_LOG_ERROR, "Invalid segment filename template '%s'\n", s->filename);
         return AVERROR(EINVAL);
     }
-    av_strlcpy(seg->cur_entry.filename, oc->filename, sizeof(seg->cur_entry.filename));
+
+    /* copy modified name in list entry */
+    size = strlen(av_basename(oc->filename)) + 1;
+    if (seg->list_entry_prefix)
+        size += strlen(seg->list_entry_prefix);
+
+    seg->cur_entry.filename = av_mallocz(size);
+    if (!seg->cur_entry.filename)
+        return AVERROR(ENOMEM);
+    snprintf(seg->cur_entry.filename, size, "%s%s",
+             seg->list_entry_prefix ? seg->list_entry_prefix : "",
+             av_basename(oc->filename));
+
     return 0;
 }
 
@@ -303,6 +317,7 @@ static int segment_end(AVFormatContext *s, int write_trailer, int is_last)
             if (seg->list_size && seg->segment_count > seg->list_size) {
                 entry = seg->segment_list_entries;
                 seg->segment_list_entries = seg->segment_list_entries->next;
+                av_free(entry->filename);
                 av_freep(&entry);
             }
 
@@ -746,6 +761,7 @@ fail:
     cur = seg->segment_list_entries;
     while (cur) {
         next = cur->next;
+        av_free(cur->filename);
         av_free(cur);
         cur = next;
     }
@@ -766,6 +782,7 @@ static const AVOption options[] = {
     { "live",              "enable live-friendly list generation (useful for HLS)", 0, AV_OPT_TYPE_CONST, {.i64 = SEGMENT_LIST_FLAG_LIVE }, INT_MIN, INT_MAX,    E, "list_flags"},
 
     { "segment_list_size", "set the maximum number of playlist entries", OFFSET(list_size), AV_OPT_TYPE_INT,  {.i64 = 0},     0, INT_MAX, E },
+    { "segment_list_entry_prefix", "set prefix to prepend to each list entry filename", OFFSET(list_entry_prefix), AV_OPT_TYPE_STRING,  {.str = NULL}, 0, 0, E },
 
     { "segment_list_type", "set the segment list type",                  OFFSET(list_type), AV_OPT_TYPE_INT,  {.i64 = LIST_TYPE_UNDEFINED}, -1, LIST_TYPE_NB-1, E, "list_type" },
     { "flat", "flat format",     0, AV_OPT_TYPE_CONST, {.i64=LIST_TYPE_FLAT }, INT_MIN, INT_MAX, E, "list_type" },

libavformat/version.h

@@ -31,7 +31,7 @@
 
 #define LIBAVFORMAT_VERSION_MAJOR 55
 #define LIBAVFORMAT_VERSION_MINOR 21
-#define LIBAVFORMAT_VERSION_MICRO 101
+#define LIBAVFORMAT_VERSION_MICRO 102
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
                                                LIBAVFORMAT_VERSION_MINOR, \