[gst-devel] When to do initial seek; segment seek problems

[Zaheer Merali]

You dont need special access to file bugs.  Just sign up for a
bugzilla account at http://bugzilla.gnome.org

There's a link on the front page:

don't have an account yet?
register today!

and it will create you an account so you can file bugs.

Zaheer

On 3/27/06, Артём Попов <artfwo at gmail.com> wrote:
> Hi guys!
> I've been trying to put together a small gstreamer app and ran into 2 problems:
> (using gst-python, all libs and plugins from latest 0.10 tarballs)
>
> 1. I want to play a small chunk of a media file using playbin.
> However, when I call the seek routine immediately after starting the
> pipeline, element_seek returns TRUE but no seeking is done:
>
>         playbin.set_state (gst.STATE_PLAYING)
>         playbin.seek (1.0, gst.FORMAT_TIME, gst.SEEK_FLAG_ACCURATE |
> gst.SEEK_FLAG_FLUSH | gst.SEEK_FLAG_SEGMENT, gst.SEEK_TYPE_SET, 25 *
> gst.SECOND, gst.SEEK_TYPE_SET, 35 * gst.SECOND)
>
> I'm calling seek too early here... So I guess that I should call seek
> right immediately after some event has happened: a handoff,
> notify_caps or something like that, right? I.e. when the pipeline
> knows more of its media stream? How could I do that??
>
> 2. I wrote a little python script to test loop-with-segment-seek
> behaviour (attached). It shows rather weird behaviour with any codec,
> that I tried to test, except WAV. I shall describe the behaviour
> below, because I'm almost sure there're bugs in the appropriate
> plugins:
>
> * WAV:
> Works okay, loops seamlessly, even with SEEK_FLAG_ACCURATE.
>
> * Ogg Vorbis:
> Starts to loop, but shortly after that (~1/2 of supposed loop) sound
> goes off and I see huge CPU load in the System Monitor Applet.
> When time comes for the loop to start over, it starts over ok with
> sound, then again sound goes off and I see huge CPU load again...
>
> * MP3 (cbr & vbr):
> The segment starts much earlier than supposed to. Lasts also much
> shorter than supposed to.
> Then the playbin spawns lots of SEGMENT_DONE messages one immediately
> after another, playback position advances far beyond stream duration
> to infinity, no sound at all.
>
> * FLAC:
> Sends EOS message instead of SEGMENT_DONE, although there's
> FLAG_SEGMENT set during seek. This is surely a bug. Requires
> SEEK_FLAG_FLUSH when restarting loop after that, which I think
> controverses with this:
> http://webcvs.freedesktop.org/gstreamer/gstreamer/docs/design/part-seeking.txt?view=markup
>
> * Fluendo mp3 plugin from SVN:
> I think this one does not know anything about segments. Emits neither
> EOS nor SEGMENT_DONE upon completion and continues to play happily
> beyond segment-end-point :(
>
> As, I already said, WAV works perfectly, so there're probably bugs in
> the other plugins. Could anyone with a bugzilla access file the bugs
> against these problems?
>
> Then again, maybe I'm doing something wrong, so I've attached the test
> program for interested people to try out. Change URI and START/STOP
> constants in the beginning of the file to test different codecs. The
> script plays file for 5 seconds, then seeks to the specified position,
> continuously printing current playback position.
>
> Thanks in advance for any hints on my problem!
> --Artem
>
>
>