Playback speed and playbin - do they work together?

[Tim Müller]

On Wed, 2014-05-07 at 19:00 +0300, Alexandru Palade wrote:

Hello Alexandru,

> I'm trying to make a combination of playbin example[1], and playback
> speed example[2]. I want a video to loop indefinitely (using
> about-to-finish signal), but I would like to be able to control the
> speed as well. Here[3]'s my experiment so far. It works, but I do have
> quite a few problems:
> 
> 1) when the video is finished and it goes at the beginning, the
> playback speed reverts to the original one. Only after I send a
> send_seek_event by pressing a key it goes back to what is supposed to
> be.
> 2) when the video is finished playing and it needs to start again,
> sometimes, it gets stuck for a few seconds and only then starts
> playing again. Again, calling send_seek_event unfreezes it.
> 
> 
> The whole day I tried to:
> a) send_seek_event in 'about-to-finish' callback, it appears to fix
> #2, but not #1
> b) listen on the bus for STREAM_START message and call send_seek_event
> then, doesn't work because it can't query the position in at line 28.
> c) listen on the bus for STATE_CHANGED message and try to call
> send_seek_event on different combinations of old state and new state,
> but I always ended up in crashing the program
> d) listen on the bus of ASYNC_DONE message and combined it with
> STREAM_START, still no luck.
> 
> 
> I'm assuming now that somehow the state of the playbin is important
> when to call that send_seek_event so that playbin can restore the
> playback speed, but I'm out of ideas where to try it. I've read on
> playbin's documentation page that it should have no problem in taking
> gst_element_send_event.

For looping the same file there's a better approach than using the
about-to-finish signal:

 - set playbin to PAUSED state
 - wait for ASYNC_DONE message on bus
 - send a seek for start=0, stop=-1 with flags FLUSH | SEGMENT
 - set playbin to PLAYING state
 - now you will get a SEGMENT_DONE message on
   the bus when the demuxer/parser is finished
   with the file (but there's still data buffered,
   so playback hasn't finished yet)
 - when you get SEGMENT_DONE, do a non-flushing
   SEGMENT seek back to start=0,stop=-1
 - wait for next SEGMENT_DONE message on the bus
 - etc.

You can determine the rate with the seek event.

If you need to change the rate dynamically during playback, you might
want to have a look at the 'frame stepping' API and examples, which let
you do that as well.


> Oh, and I'm in 1.x branch.

Excellent.

Cheers
 -Tim

-- 
Tim Müller, Centricular Ltd - http://www.centricular.com