Information About Segment Event

[Thiago Santos]

On 05/20/2014 09:03 AM, Manoj89 wrote:
> Hi,
>     I wanted to know whether the segment event is fired by the source or
> demuxer element by itself  or we can make a particular element in the
> pipeline(for ex : source) to send an segment event.
Every element must send a segment event before pushing data. What 
happens is that elements can also just relay the segment they receive on 
the sink pad downstream without modification. So the answer is yes as 
every element must push a segment event before data for each of its 
source pads.

I guess your question is more related to when just relay upstream 
segment or create a new one, this depends on what makes sense for your 
pipeline/element. I'll give you the example of playback of a file. The 
filesrc will create and push a segment event in *bytes* as this is how 
the data from a filesrc is limited, from byte at position A to byte at 
position B, respectively the start and stop position in GstSegment. 
Those are usually 0 and -1 as you usually want to read the whole file 
but I guess you get the point. This segment event will just be forwarded 
by every element in the pipeline until it reaches the demuxer, the 
demuxer will get the file input and convert that into 
video/audio/subtitle streams, at this point it doesn't make sense to 
"speak" in bytes anymore but in "time" as this is much more useful than 
knowing the byte range of a certain video/audio sample in the original 
file. So the demuxer creates a new segment in *time* format and pushes 
it on its source pads and it doesn't forward the segment it received in 
*bytes* because that doesn't make sense for its streams.

Of course you can have source elements that use *time* segments like 
camera sources (v4l2src). So it all depends on your elements and 
pipeline. Do you have a particular scenario in mind?

>
>
>
> --
> View this message in context: http://gstreamer-devel.966125.n4.nabble.com/Information-About-Segment-Event-tp4667048.html
> Sent from the GStreamer-devel mailing list archive at Nabble.com.
> _______________________________________________
> gstreamer-devel mailing list
> gstreamer-devel at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel


-- 
Thiago Sousa Santos
Senior Multimedia Engineer, Open Source Group
Samsung Research America - Silicon Valley