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

[suman kolaganti]

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 ?

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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