今天又简单阅读了下HTTP Live Streaming - draft-pantos-http-live-streaming...

将07与01对比着看很有意思：( 跨度大才更容易发现变化，然后问一个为什么？ )，eg:

#       The Playlist file           #

# draft-pantos-http-live-streaming-01

   3.  The Playlist file  . . . . . . . . . . . . . . . . . . . . . .  4
     3.1.  New Tags . . . . . . . . . . . . . . . . . . . . . . . . .  5
       3.1.1.  EXT-X-TARGETDURATION . . . . . . . . . . . . . . . . .  5
       3.1.2.  EXT-X-MEDIA-SEQUENCE . . . . . . . . . . . . . . . . .  5
       3.1.3.  EXT-X-KEY  . . . . . . . . . . . . . . . . . . . . . .  6
       3.1.4.  EXT-X-PROGRAM-DATE-TIME  . . . . . . . . . . . . . . .  6
       3.1.5.  EXT-X-ALLOW-CACHE  . . . . . . . . . . . . . . . . . .  6
       3.1.6.  EXT-X-ENDLIST  . . . . . . . . . . . . . . . . . . . .  7
       3.1.7.  EXT-X-STREAM-INF . . . . . . . . . . . . . . . . . . .  7

#  draft-pantos-http-live-streaming-07

   3.  The Playlist file  . . . . . . . . . . . . . . . . . . . . . .  4
     3.1.  Introduction . . . . . . . . . . . . . . . . . . . . . . .  4
     3.2.  Attribute Lists  . . . . . . . . . . . . . . . . . . . . .  6
     3.3.  New Tags . . . . . . . . . . . . . . . . . . . . . . . . .  7
       3.3.1.  EXT-X-BYTERANGE  . . . . . . . . . . . . . . . . . . .  7
       3.3.2.  EXT-X-TARGETDURATION . . . . . . . . . . . . . . . . .  7
       3.3.3.  EXT-X-MEDIA-SEQUENCE . . . . . . . . . . . . . . . . .  8
       3.3.4.  EXT-X-KEY  . . . . . . . . . . . . . . . . . . . . . .  8
       3.3.5.  EXT-X-PROGRAM-DATE-TIME  . . . . . . . . . . . . . . .  9
       3.3.6.  EXT-X-ALLOW-CACHE  . . . . . . . . . . . . . . . . . .  9
       3.3.7.  EXT-X-PLAYLIST-TYPE  . . . . . . . . . . . . . . . . .  9
       3.3.8.  EXT-X-ENDLIST  . . . . . . . . . . . . . . . . . . . . 10
       3.3.9.  EXT-X-MEDIA  . . . . . . . . . . . . . . . . . . . . . 10
         3.3.9.1.  Rendition Groups . . . . . . . . . . . . . . . . . 11
       3.3.10. EXT-X-STREAM-INF . . . . . . . . . . . . . . . . . . . 12
         3.3.10.1. Alternative Renditions . . . . . . . . . . . . . . 13
       3.3.11. EXT-X-DISCONTINUITY  . . . . . . . . . . . . . . . . . 14
       3.3.12. EXT-X-I-FRAMES-ONLY  . . . . . . . . . . . . . . . . . 14
       3.3.13. EXT-X-I-FRAME-STREAM-INF . . . . . . . . . . . . . . . 15
       3.3.14. EXT-X-VERSION  . . . . . . . . . . . . . . . . . . . . 15

#        EXT-X-MEDIA-SEQUENCE           #

# draft-pantos-http-live-streaming-01

 3.1.2.  EXT-X-MEDIA-SEQUENCE

   Each media file URI in a Playlist has a unique sequence number.  The
   sequence number of a URI is equal to the sequence number of the URI
   that preceded it plus one.  The EXT-X-MEDIA-SEQUENCE tag indicates
   the sequence number of the first URI that appears in a Playlist file.
   Its format is:

   #EXT-X-MEDIA-SEQUENCE:<number>

   If the Playlist file does not contain an EXT-X-MEDIA-SEQUENCE tag
   then the sequence number of the first URI in the playlist SHALL be
   considered to be 1.                           # draft-pantos-http-live-streaming-03起修改为0

# draft-pantos-http-live-streaming-07

3.3.3.  EXT-X-MEDIA-SEQUENCE

   Each media URI in a Playlist has a unique integer sequence number.
   The sequence number of a URI is equal to the sequence number of the
   URI that preceded it plus one.  The EXT-X-MEDIA-SEQUENCE tag
   indicates the sequence number of the first URI that appears in a
   Playlist file.  Its format is:

   #EXT-X-MEDIA-SEQUENCE:<number>

   A Playlist file MUST NOT contain more than one EXT-X-MEDIA-SEQUENCE
   tag.  If the Playlist file does not contain an EXT-X-MEDIA-SEQUENCE
   tag then the sequence number of the first URI in the playlist SHALL
   be considered to be 0.

  A media URI is not required to contain its sequence number.

#         Loading the Playlist file           #

# draft-pantos-http-live-streaming-01

6.2.1.  Loading the Playlist file

   Every time a Playlist file is loaded or reloaded from the Playlist
   URI:

      The client SHOULD check that the Playlist file begins with #EXTM3U
      and refuse to continue if it does not.  The client SHOULD ignore
      any tags it does not recognize.

      The client MUST determine the next media file to load as described
      in Section 6.2.4.

   If the Playlist contains the EXT-X-MEDIA-SEQUENCE tag, the client
   SHOULD assume that each media file in it will become unavailable at
   the time that the Playlist file was loaded plus the duration of the
   Playlist file.  The duration of a Playlist file is the sum of the
   durations of the media files within it.

# draft-pantos-http-live-streaming-07

6.3.2.  Loading the Playlist file

   Every time a Playlist file is loaded or reloaded from the Playlist
   URI:

      The client MUST ensure that the Playlist file begins with the
      EXTM3U tag and that the EXT-X-VERSION tag, if present, specifies a
      protocol version supported by the client; if not, the client MUST
      NOT attempt to use the Playlist.

      The client SHOULD ignore any tags and attributes it does not
      recognize.

      The client MUST determine the next media segment to load, as
      described in Section 6.3.5.

   If the Playlist contains the EXT-X-MEDIA-SEQUENCE tag, the client
   SHOULD assume that each media segment in it will become unavailable
   at the time that the Playlist file was loaded plus the duration of
   the Playlist file.

这个世界变化太快了。。。