[gst-devel] Suggestion needed while Metadata Reading & Writing to a large files via Gstreamer

[Stefan Kost]

suman kolaganti wrote:
> Dear Team,
>
>
> I am  involved in development of UI program that reads & writes
> metadata to a video MP4 files.
> Reading & writing is done by lower level library, apart from UI
> program, which also implemented by me.
> This is the design implementation from lower-library is to read metadata from a video:
>
> 1.
> using a  g_main_loop_new (NULL, FALSE);                                --> with default context
>
>
> 2.
> getting a bus from a pipeline & adding a bus watch  for the gst_messages   and upon EOS / in-case any error /Paused state , iam quitting the mainloop.
>
> bus = gst_pipeline_get_bus (GST_PIPELINE (self->pipeline));
>
> gst_bus_add_watch (bus, bus_call, (gpointer)self);
>
>
> 3. The UI program is inturn having a g_main_loop and invoking this lower-library api for reading & writing the metadata  .
>
>
> There are asyncrounous things  happening .Reasons:
>
>
> i) since in case of large video files the lower-library is taking long time while reading or witing metadata .
> ii) mean while if we do any UI operations ..let us say suppose the same file is deleted . In this case .. before the control commes out of that lower-level api , the file is subjected to delete .
>
> this resulting in improper behavior .
>
>
> Is there any possibility of the 2 gmainloops  mixing with each other ..?
> Is there any alternative  ..so that  we can remove the g_main_loop from lower-libray  and use some other approach ?
>
> How to avoid g_main_loop in lower level Library ?can i replace with any..?
> How can i make this syncronous ?
>   

Why can't you add signals to your lower library to signal that the
tag-operation has finished. Then you can leave it async. If you make it
sync, you will anyway block your ui for too long.

Stefan

> i tried  with few :
> 1.
> creating new context in lowwer-library :
> I tried with context = g_main_context_new() and creating the loop = g_main_loop_new(context,FALSE) with that context .
>
> resulting in freezing upon g_main_loop_run(loop).
>
> 2.
> Instead of gst_bus_add_watch()  , i used gst_bus_add_signal_watch () as shown below :
>
> here i removed g_main_loop & used g_main_iteration() Api until EOS/Error 
>
>
> Stability  of the reading/writing tags is undefined, some times this works & some it wont . 
>
> 3)link: 
> http://gstreamer.freedesktop.org/data/doc/gstreamer/head/manual/html/chapter-bus.html
>
>
> last 2 lines states that :
>
> If you aren't using GLib mainloop, the asynchronous message signals won't
>       be available by default. You can however install a custom sync handler
>       that wakes up the custom mainloop and that uses
>
>       |gst_bus_async_signal_func ()| to emit the signals.
>       (see also documentation <http://gstreamer.freedesktop.org/data/doc/gstreamer/stable/gstreamer/html/GstBus.html> for details)
>
>     
> didnt get the idea ,how to implement this async handler ..
> Please suggest ...
>
>   
> 4)
> Please suggest if any more ideas ...
>
>
> Thanks & Regards,
> suman.
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