[FFmpeg-trac] #1642(avformat:closed): -f segment: automagically generate #EXTM3U tags to -segment_list generated playlists

[FFmpeg]

#1642: -f segment: automagically generate #EXTM3U tags to -segment_list generated
playlists
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             Reporter:  kelexel      |                    Owner:
                 Type:  enhancement  |                   Status:  closed
             Priority:  normal       |                Component:  avformat
              Version:  git-master   |               Resolution:  fixed
             Keywords:  segment,     |               Blocked By:
  HLS, m3u8                          |  Reproduced by developer:  1
             Blocking:               |
Analyzed by developer:  1            |
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Comment (by kelexel):

 Hi, first of all, many thanks for the time invested in this issue.

 Now, the real issue resides in the #EXT-X-TARGETDURATION being written at
 the end of the file.
 Because it is only written when ffmpeg exepects to have reached the end of
 the file, it will really, definitely, break HLS.

 Keep in mind I am talking about fetching a live (RTMP in my case) feed,
 for which you have no clue of when the feed ends - so no clue of when you
 will invoke segment_list_close)

 All I can do is encourage you to check by yourself, using any source file
 and -f segment, outputing mpegts files to a dir, and use an iOS device to
 read said files.
 The playlist will be read by the client each time the client will reach
 the last file specified in the playlist, and keep doing it until it
 eventually reaches a #EXT-X-ENDLIST) in said playlist.
 If the iOS device has no clue of the segment length it should expect, it
 will miserably fail to read said stream (at least on iOS 5.x)

 So, once again, your patch will work for known duration files, i.e.: I'm
 transcoding a file, because the client will find in the playlist, at the
 end, both the EXT-X-TARGETDURATION and mostly EXT-X-ENDFILE tags, so the
 iOS device and mobile safari will be happy and know where your steam
 starts, when it ends and in how many segments it should expect it.
 But this logic breaks HTTPLiveStream !
 I won't argue on the pseuso scarse (I agree) RFC on m3u8.
 But real-life tests show that if that tag is not present at the top of the
 file, it will simply not work.
 iOS devices need to know that tag to accept reading the mpeg2ts segments.
 If it doesn't find that tag it simply throws an error. When you are doing
 live transcoding of a current video stream,  you have no idea when the
 stream will end, so your only chance is to put that tag in
 segment_list_open and really not in segment_list_close

 I am not arguing who patched what first, I am not a developer, just an
 aware-user.
 All I can say is that if you use my (dirty) patch on previous sources,
 your iOS device will play a live and pre-recorded stream fine.
 But, if you use your patch, than iOS devices will only play pre-recorded
 streams, and fail to play live-transcoded streams.

 That's all I'm trying to point out.

 With all due respect to you and the ffmpeg community.

 Please consider modifying your patch.

 Best regards.

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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/1642#comment:6>
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