<div dir="ltr">Do you think that gst_message_new_request_state() [1] could be of any help here?<div><br><div style>Is it worthwhile to send a request on behalf of the new live element to set it to playing and handle it in a more controlled manner in the main application rather than from within a custom bin in the context of the typefinder? This would be a work-around I guess as the core issue still exists [2].</div>
<div style><br></div><div>[1] <a href="http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gstreamer/html/gstreamer-GstMessage.html#gst-message-new-request-state">http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gstreamer/html/gstreamer-GstMessage.html#gst-message-new-request-state</a></div>
</div><div>[2] <a href="https://bugzilla.gnome.org/show_bug.cgi?id=632782" target="_blank" style="font-size:13px;font-family:arial,sans-serif">https://bugzilla.gnome.org/show_bug.cgi?id=632782</a></div><div><br></div><div style>
Cheers,</div><div style>Kris</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">2013/4/2 Krzysztof Konopko <span dir="ltr"><<a href="mailto:krzysztof.konopko@gmail.com" target="_blank">krzysztof.konopko@gmail.com</a>></span><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">OK, after some debugging I've come across a comment in gsturidecodebin.c that led me to this bug:<div>
<a href="https://bugzilla.gnome.org/show_bug.cgi?id=632782" target="_blank">https://bugzilla.gnome.org/show_bug.cgi?id=632782</a><br>
</div><div><br></div><div>Looks like instantiating live elements through type-finding either does not work or at least it's racy.</div><div>If this is all true and if there are any ideas of fixing it, I'd be tempted to have a look and tinker a little bit with it.</div>
<div><br></div><div>Cheers,</div><div>Kris</div></div><div class="HOEnZb"><div class="h5"><div class="gmail_extra"><br><br><div class="gmail_quote">2013/3/28 Krzysztof Konopko <span dir="ltr"><<a href="mailto:krzysztof.konopko@youview.com" target="_blank">krzysztof.konopko@youview.com</a>></span><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Interestingly /decodebin2/ does not propagate instantiated element's<br>
GstStateChangeReturn return value as it's a type-found signal callback.<br>
gst-plugin-base/gst/playback/gstdecodebin2.c:connect_pad():<br>
<br>
/* Bring the element to the state of the parent */<br>
if ((gst_element_set_state (element,<br>
GST_STATE_PAUSED)) == GST_STATE_CHANGE_FAILURE) {<br>
<br>
so no way to say there will be no pre-roll.<br>
<br>
Does it make any sense to try to instantiate a live element through<br>
typfinding?<br>
<br>
Cheers,<br>
Kris<br>
<div><div><br>
On 11/01/13 17:05, Krzysztof Konopko wrote:<br>
> Hi,<br>
><br>
> I had a closer look into it. The problem can be reduced to something<br>
> like this (hope you don't mind if I rehash some bits of previous<br>
> description):<br>
><br>
> gst-launch-1.0 \<br>
> uridecodebin uri=file:///tmp/test.sdp caps=video/mpegts \<br>
> ! fakesink<br>
><br>
> On my laptop it doesn't matter whether it's a genuine HTTP or filesystem<br>
> request. It deadlocks.<br>
><br>
><br>
> There's a custom vqesdpdemux element which has application/sdp<br>
> capability on its sink. Here's how the gist of the problem goes:<br>
><br>
> 1. uridecodebin instantiates filesrc, queue2 and vqesdpdemux (typefinder<br>
> magic)<br>
><br>
> 2. vqesdpdemux receives data (buffers) from filesrc until it gets EOS<br>
> event on its sink pad (receives SDP content, simple text file)<br>
><br>
> 3. In the same thread were the EOS event was received vqesdpdemux<br>
> (GstBin) creates a genuine custom vqesrc element which is supposed to<br>
> receive the RTP traffic<br>
><br>
> 4. The new vqesrc element's state is synchronised with its parent<br>
> (vqesdpdemux) by calling gst_element_sync_state_with_parent() but this<br>
> can "trap" it in PAUSED or READY state (depends how far in the<br>
> transition the pipeline got after sending EOS).<br>
><br>
> Now because vqesrc is a *live* element, it's activated pad thread waits<br>
> in gst_base_src_wait_playing() for vqesrc to get into PLAYING. But it<br>
> won't transition to that state if it's "trapped" in pipeline's<br>
> transition towards READY (depending on timing conditions).<br>
><br>
><br>
><br>
> I'll be digging into it (*) but if it bells with anyone, please shout.<br>
><br>
> Basically we're looking for (or trying to find/understand) a good<br>
> pattern to create a new source element somewhere in the *middle* of the<br>
> pipeline based on some information (buffers) already received and<br>
> potentially ditch/replace (lop off) the old bit of upstream (if<br>
> possible) after it's done its job.<br>
><br>
> It works pretty well if the source is explicit (e. g. filesrc). Things<br>
> get complicated if one wants to use typefind magic and<br>
> auto-instantiating/connecting (some decodebin element).<br>
><br>
> Cheers,<br>
> Kris<br>
><br>
> (*) It's a quite involving piece of work to looking into. I'm not doing<br>
> it because I'm magnanimous but because Mariusz is sitting almost next to<br>
> me :)<br>
><br>
> On 07/01/13 17:57, Mariusz Buras wrote:<br>
>> Hi all,<br>
>><br>
>> I have a quite complex problem to describe so first I'll show you my<br>
>> pipeline setup:<br>
>><br>
>> uridecodebin uri=<a href="http://some_address_somewhere.co.uk/test.sdp" target="_blank">http://some_address_somewhere.co.uk/test.sdp</a><br>
>> caps=video/mpegts<br>
>> ! queue ! tsdemux ! video/x-h264 ! decodebin ! queue ! xvimagesink<br>
>><br>
>> Where "test.sdp" is an SDP file which refers to a multicast RTP stream.<br>
>> I have created an element "vqesrc"[1] which is a live source for this<br>
>> multicast RTP data. It takes the contents of an SDP file as a property.<br>
>> To get it to be autoplugged by decodebin I have also created<br>
>> vqesdpdemux which handles "application/sdp" caps much like hlsdemux or<br>
>> sdpdemux works.<br>
>><br>
>> vqesdpdemux is a bin. It creates a vqesrc, adds it to itself, sets the SDP<br>
>> file data as a one of the properties of vqesrc and adds a ghost pad on<br>
>> vqesdpdemux exposing the source pad of the gstvqesrc to outside of the<br>
>> bin. So when everything works I should be getting something like that on<br>
>> the diagram[2]. As you can see everything gets autoplugged as expected<br>
>> and I indeed can see live video on my screen. I have also attached a log<br>
>> file that shows what's going on when it works [3].<br>
>><br>
>> In vqesdpdemux when I create the vqesrc child element (which is a live<br>
>> source) I am careful to call gst_element_sync_state_with_parent for the<br>
>> child. Also I am careful to return GST_STATE_CHANGE_NO_PREROLL from<br>
>> vqesdpdemux whenever a request to enter state PAUSED is received as I<br>
>> know the child I will be adding will be live.<br>
>><br>
>><br>
>> The problem starts when uridecodebin is pointed to a locally stored SDP<br>
>> file, something like this:<br>
>><br>
>> uridecodebin uri=file:///home/mariusz.buras/tmp/test.sdp<br>
>> caps=video/mpegts<br>
>> ! queue ! tsdemux ! video/x-h264 ! decodebin ! queue ! xvimagesink<br>
>><br>
>> Basically, what seems to happen is that my pipeline never fully enters<br>
>> PAUSED state (only vqesdpdemux does) and gets stuck in READY forever.<br>
>> As shown in [4] pipeline start to preroll but never finishes. My<br>
>> experiments showed that in "http case" SDP file is delivered while the<br>
>> pipline is changing it's state to PLAYING. While in the "broken" case<br>
>> it's delivered when the pipeline is transitioning to the PAUSED state.<br>
>> This leads me to believe that something wrong happens (or something good<br>
>> doesn't happen) when vqesdpdemux receives a sink event callback with a<br>
>> buffer containing the SDP file.<br>
>><br>
>> What I have tried to fix/mitigate the problem*:<br>
>><br>
>> 1. Forcing vqesrc element state to PLAYING just after it's added to<br>
>> vqesdpdemux bin with gst_set_state rather than<br>
>> gst_element_sync_state_with_parent. This makes it work, but I don't<br>
>> think this is a right thing to do. It makes me a bit uneasy using a<br>
>> half baked "fix" to a problem I don't understand.<br>
>> 2. Sending a reconfigure event. Doesn't help.<br>
>> 3. Delaying the creation of vqesrc element - this doesn't work.<br>
>> 4. Plenty of weird/desperate hacks on vqesdpdemux - same result.<br>
>><br>
>> * when I write that "it doesn't work" I mean that it behaves in the same<br>
>> or very similar fashion to when the "fix" wasn't applied.<br>
>><br>
>> I've also attached [5] a diagram of the last state the pipeline gets<br>
>> into when it doesn't work. This is not very helpful though, because<br>
>> the last state my pipeline fully enters is READY when no auto-plugging<br>
>> happened yet.<br>
>><br>
>><br>
>> I think possibly what is happening is that the pipeline is prerolling in<br>
>> the PAUSED state so vqesrc doesn't produce any data so the pipeline<br>
>> never exits the prerolling state so makes it to state PLAYING but then<br>
>> I'm unsure why it would work with the http case but not with local file.<br>
>><br>
>><br>
>> Can someone help me with that?<br>
>><br>
>> Regards,<br>
>> Mariusz.<br>
>><br>
>><br>
>> [1] The code for both of these can be found on github:<br>
>> <a href="https://github.com/sqward/gst-vqe" target="_blank">https://github.com/sqward/gst-vqe</a><br>
>> [2] An example working pipeline attached as "example_working_pipeline.jpg"<br>
>> [3] An example working log attached as "example_working_log.txt"<br>
>> [4] Log of a broken case attached as "broken_case.txt"<br>
>> [5] A diagram of "broken" pipeline when it gets stuck in READY state<br>
>> attached as "broken_case.png"<br>
>><br>
>><br>
>><br>
>> _______________________________________________<br>
>> gstreamer-devel mailing list<br>
>> <a href="mailto:gstreamer-devel@lists.freedesktop.org" target="_blank">gstreamer-devel@lists.freedesktop.org</a><br>
>> <a href="http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel" target="_blank">http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel</a><br>
>><br>
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</blockquote></div><br></div>
</div></div></blockquote></div><br></div>