OpenGL Texture via GstGLUpload - So close! - Proper Post
Lasse Laursen
lasse at lasselaursen.com
Sat Jan 17 03:47:50 PST 2015
Hey again,
I can almost taste success. I imagine it being sweet, like sugar.
Entirely unlike the bitter lemony sourness of 'not quite there' I have
in my mouth now. Help me see the error of my ways!
Inspired by the code Matthew sent my way, I've cobbled together the
following object in C++ that is supposed to create a pipeline, share the
current OpenGL context with it, grab samples arriving at the appsink and
provide the texture ID's to the main thread for usage.
videoTester.h
http://hastebin.com/sutoyuxoci.coffee
videoTester.cpp
http://hastebin.com/gohofababi.cpp
In the main application, the following happens:
Cinder sets up all the win32 app stuff, including an OpenGL context.
VideoTester4 is instantiated with paths pointing to a webm video and a
passthrough fragment shader (no parameters).
prepPipeline() is called.
launchPipeline() is called.
The generated Texture ID is inspected via imdebug (an awesome texture
debugging tool) via this call:
imdebugTexImage( GL_TEXTURE_2D, mVidTester4->getTexId(), GL_RGBA );
Note that I intentionally do *not* unref any of the associated
frame/sample/buffer objects, just to keep things simple. However, all I
seem to get when I use imdebug to inspect the textures, are empty 0,0
sized textures that (not surprisingly) contain nothing at all. I
wondered if GL_TEXTURE_2D might be the wrong texture target and have
also tried GL_TEXTURE_RECTANGLE without any luck. Is there any place I
can read the texture target from?
Anyway, the pipeline does not report any errors along the way, and the
gstreamer log only contains a few (harmless?) warnings:
0:00:00.683792474 1836 0CFBEE60 WARN gldisplay
gstgldisplay.c:169:gst_gl_display_new: Could not create display. user
specified (NULL) (platform: (NULL)), creating dummy
0:00:00.686256033 1836 0CFBEE60 WARN basesrc
gstbasesrc.c:3470:gst_base_src_start_complete:<source> pad not activated yet
0:00:00.686752850 1836 0CFBEE60 WARN basesrc
gstbasesrc.c:3470:gst_base_src_start_complete:<source> pad not activated yet
The texture ID increases as the program continues execution (which is to
be expected), and inspecting the Textures in the actual callback thread
with imdebug crashes the program. This has to be due to the fact that
the callback function executes in a separate thread as Matthew told me
last we spoke.
I've poked a bit around with the various Gst objects without any luck so
far. Any ideas/clues as to what I'm missing or how to narrow down what
the problem might be?
Regards,
Lasse
On 16-01-2015 22:21, Matthew Waters wrote:
>
> On 17/01/15 06:42, Lasse Laursen wrote:
>> Hey Matthew,
>>
>> Thanks for the reply and especially the example. I'm working on
>> getting it function with the cinder framework. At first it seemed
>> quite odd to hand over the context as a result of a bus message, but
>> I can see the logic in not needing to create a secondary OpenGL
>> context for gstreamer to make textures in, if one already exists. I
>> do have one question though:
>>
>> Is it vital to turn off the OpenGL context when sharing it with
>> Gstreamer? I've done a little context sharing before and I don't
>> recall having to actively turn any contexts 'off'.
>
> No it is not required to turn off the context.
>
>> Regards,
>> Lasse
>>
>> On 16-01-2015 00:27, Matthew Waters wrote:
>>> A couple of points added inline.
>>>
>>> On 16/01/15 03:14, Lasse Laursen wrote:
>>>> Hello!
>>>>
>>>> Apologies for the double post, but my inept handling of Thunderbird
>>>> caused my last post to be appended to an unrelated thread. Sorry
>>>> about that Luis dArquer.
>>>>
>>>> For the sake of posterity, here's is the original question:
>>>>
>>>> I feel like I am so close to finally getting through to the other
>>>> side with this problem, so I'm hoping someone can give me a few
>>>> clues as to what pieces of the puzzle are missing. I used to use
>>>> gStreamer as a pure 'decoding' library using this simple pipeline:
>>>>
>>>> uridecodebin uri=" + mPathToVideoFile + " ! videoconvert !
>>>> appsink name=sink
>>>> caps="video/x-raw,format=RGB,pixel-aspect-ratio=1/1";
>>>>
>>>> With this pipeline, I could quite easily grab the frames arriving
>>>> at the sink and use them however I pleased. Mostly just throwing
>>>> them on a texture in OpenGL and displaying them various places.
>>>> This approach is - of course - quite horrible. I'm not making use
>>>> of gstreamer as a fully-fledged media pipeline. So to rectify that
>>>> - and because I'd like to run some simple shaders on the video data
>>>> - I am now using this (almost as) simple pipeline:
>>>>
>>>> uridecodebin uri=" + mPathToVideoFile + " ! glshader name=shader
>>>> location=" + pathToShader + " vars=\"float silver = float( 0.8 );
>>>> \" ! appsink name=sink
>>>> caps=\"video/x-raw,format=RGB,pixel-aspect-ratio=1/1\"";
>>>
>>> 1. You should set the appsink caps to contain the memory:GstGLMemory
>>> caps features. e.g. video/x-raw(memory:GstGLMemory),format=RGBA...
>>> see gst-inspect-1.0 glshader for the supported formats and
>>> features. Otherwise, glshader (and any GL element) will download
>>> the texture upon seeing the system memory caps.
>>>
>>>> I make sure to share my current OpenGL context with the glshader
>>>> element thusly:
>>>>
>>>> mPipeline_ShaderPre = gst_bin_get_by_name( GST_BIN( mGstPipeline ),
>>>> "shader" );
>>>> HGLRC mainContext = ::wglGetCurrentContext();
>>>> g_object_set( mPipeline_ShaderPre, "other-context", mainContext,
>>>> NULL );
>>>
>>> 2. The "other-context" property expects a GstGLContext rather than a
>>> platform specific handle. You can wrap a context handle using
>>> gst_gl_context_new_wrapped(). However, in master there is no
>>> "other-context" property anymore so the sharing of GL context
>>> happens using GstContext. See for example
>>> http://cgit.freedesktop.org/gstreamer/gst-plugins-bad/tree/tests/examples/gl/sdl/sdlshare.c#n232
>>> and the GstContext documentation.
>>>
>>>> Not sure if this is correct to be honest, but I didn't see any
>>>> errors in gstreamers logs. Anyway - fast forward to my callback
>>>> function that fires whenever a sample is ready at the sink I
>>>> proceed to grab a Sample, from which I grab a Buffer, from which I
>>>> grab a Frame, from which I grab a Texture ID, thusly:
>>>>
>>>> GstSample* gstVideoSinkSample = gst_app_sink_pull_sample(
>>>> GST_APP_SINK( appsink ) );
>>>> GstBuffer* gstBuffer = gst_sample_get_buffer( gstVideoSinkSample );
>>>> if ( !gst_video_frame_map( &gstFrame, &gstInfo, gstBuffer,
>>>> static_cast<GstMapFlags>( GST_MAP_READ | ( GST_MAP_FLAG_LAST << 1 )
>>>> ) ) )
>>>> {
>>>> errorToConsole( true, "Failed to map video frame" );
>>>> }
>>>> GLuint textureId = *(guint *) gstFrame.data[0];
>>>>
>>>> The result is the number 6. Which I felt was a plausible Texture ID
>>>> handle. But when I then use a lovely tool named imdebug, and
>>>> presume that the target for the texture is GL_TEXTURE_2D (which
>>>> might be wrong), it throws a fit, because it attempts to determine
>>>> the width and height of said texture via these calls:
>>>>
>>>> glBindTexture(target, texture);
>>>> glGetTexLevelParameteriv(target, 0, GL_TEXTURE_WIDTH, &w);
>>>> glGetTexLevelParameteriv(target, 0, GL_TEXTURE_HEIGHT, &h);
>>>>
>>>> So clearly something is wrong. Some place along this winding road,
>>>> I've misunderstood something or overlooked something. I'd much
>>>> appreciate any suggestions/clues!
>>>>
>>>> I myself am wondering if a callback at the sink is the right place
>>>> to grab the texture ID, but I'm not sure how to get at it any
>>>> earlier, and if that's wise. I am also unsure of how long this
>>>> texture Id is valid if I want to render it on to a quad. I hope
>>>> someone can shed a bit of light!
>>>
>>> It will be valid for as long as it's not overwritten/reused by the
>>> producing element which generally means while you keep a ref to the
>>> buffer or have the video frame mapped.
>>>
>>>> Regards,
>>>> Lasse
>>>>
>>>> --
>>>> Lasse Farnung Laursen
>>>> Researcher at the University of Tokyo
>>>> www.lasselaursen.com <http://www.lasselaursen.com>
>>>> Twitter: @PMP_J <https://twitter.com/PMP_J>
>>>
>>>
>>> _______________________________________________
>>> gstreamer-devel mailing list
>>> gstreamer-devel at lists.freedesktop.org
>>> http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
>>
>> --
>> Lasse Farnung Laursen
>> Researcher at the University of Tokyo
>> www.lasselaursen.com <http://www.lasselaursen.com>
>> Twitter: @PMP_J <https://twitter.com/PMP_J>
>
>
>
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> gstreamer-devel mailing list
> gstreamer-devel at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
--
Lasse Farnung Laursen
Researcher at the University of Tokyo
www.lasselaursen.com <http://www.lasselaursen.com>
Twitter: @PMP_J <https://twitter.com/PMP_J>
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