[mythtv-users] HTTP live stream and seeking in .25
nick.rout at gmail.com
Wed Mar 7 23:24:13 UTC 2012
On Wed, Mar 7, 2012 at 7:38 AM, Ian Bishop <ibishop at gmail.com> wrote:
>> I'm not an expert but I have noodled around with streams a little and can
>> pass on what I know. MythTV implements http streaming as originated by Apple
>> which you can read about in their developer library document titled "HTTP
>> Live Streaming Overview". At this moment the document lives here & I believe
>> nearby is a link to a PDF.
> Sweet, well that's what I wanted to hear! I would expect the native
> Android video player to play nicely with the Apple-like stream.
According to wikipedia http live streaming is only incorporated in
android from 3.0 onwards.
> just didn't want to dive in and waste a bunch of time to find out what
> I wanted to do wasn't possible. I guess I'll need to build up a .25
> backend in a VM now. :)
>> The big picture goes like this: a server (MythTV in this case) encodes a
>> video as a series of short clips, say 10 seconds long, and supplies clients
>> with an "m3u8" file url containing the names of the segments. You retrieve
>> each segment in turn and play them back to back so it's seamless to the
>> user. If the list is open ended then it's considered to be an in-progress
>> event and you have to periodically requery the m3u8 url for the current list
>> of segments. As you might guess you can calculate the total length of the
>> video by multiplying the segment duration by the number of segments and you
>> can seek by dividing your desired position by the segment duration to get
>> the segment number and using the remainder as an offset into that clip.
>> In the previous paragraph I said "you" a few times but you personally don't
>> have to get involved at such a low level. Software such VLC will take an url
>> and do the grunt work. Or, in writing your own application you would embed a
>> video widget supplied by your O/S and have it do the grotty stuff. I'm
>> pretty sure you don't want to write your own widget, go with your OS's one.
>> Typically a widget will take an URL and play it without further prodding but
>> they also expose an api for you to query the current position, seek to a
>> given offset, pause, resume, etc. Also, widgets supply an OSD so users can
>> see where they're at and click arrows or a slider to move back and forth.
>> Your job as a programmer then becomes slicing and dicing the list of media
>> offered up by mythtv, initiating streaming transcodes, and handing off m3u8
>> urls to your embedded player.
>> That's a fairly breezy introduction but hopefully gets you oriented. It's
>> really not very complicated but there are several moving parts and at first
>> it's hard to tell where one ends and the other begins.
>> Assuming you're running a recent master you can get a decent education by
>> kicking off a stream and examining the entrails. Start by defining a
>> directory for the "Streaming" storage group (mythtv-setup -> Storage
>> Directories) and then starting a stream. In that folder you'll find the
>> expected m3u8 file but also an html file which shows how you might play a
>> stream in a browser. An Android application would be conceptually similar.
>> Aside from the video clips everything in that streaming directory will be
>> text files so snoop and learn.
>> - George
> Sounds straightforward. Thanks again for the help!
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