[gst-devel] Compositing and GStreamer
Timothy Braun
braunsquared at gmail.com
Sat Nov 27 19:50:04 CET 2010
Kapil,
Thanks for the suggestion, but with multifilesrc I would have to have the
files static with incrementing named files. A single box in the 3x2 grid
may contain the same file multiple times so I'm afraid it won't be the best
solution.
I guess, ultimately, there's multiple ways to attack this one from what
I've been able to find. Here are the two that I've been looking at, I'm
just not sure which is the better solution at this point:
- A single gnonlin composition with a 4 gnlsources similar in setup as
the gst-launch text I have below.
- 6 gnonlin compositions, each feeding to a single videomixer which
combines them into the final frame.
- This path I'm currently investigating. I have a test written in C,
but I'm having some difficulties with pad linkage as I still don't have a
complete understanding of when certain things will exist and how to get
them.
- Here's currently whats happening:
- Create a new pipeline
- Create a videomixer
- Create 6 gnonlin compositions each with a pad-added signal
callback to connect gnlcomposition pad to videomixer.
- ... (this is were it's going wrong)
- In the pad-added callback I have:
- static void onPad(GstElement *comp, GstPad *pad, GstElement
*sink) {
GstPad *v = gst_element_get_pad(sink, "sink");
gst_pad_link(pad, v);
gst_object_unref(v);
}
- gst_element_get_pad is not returning a pad from the video mixer
(sink) which leads me to believe that I'm either not asking
in the right
manner or the pad doesn't exist. (I'm aware that
gst_element_get_pad is
deprecated, I'm just looking to test at the moment)
- I noticed in one of the repositories under a unit test, the
videomixer was attached as a gnloperation? Is this the
better path to take?
This all leads me to a couple more questions as well:
- A video mixer pad has xpos and ypos properties. This would let me
shift the video around without needing a video box which I believe may be
more efficient?
- If I use the xpos and ypos properties, is the video mixer smart enough
to change the frame size appropriately or will it simply crop the frame to
the size of the largest input frame?
- If so, would it be better to add a videobox to do the adjustments
for me, or feed in a solid color background of the required output size?
Thanks again for the time. I know there's a lot of questions above, but
any help of any kind is greatly appreciated.
All the best,
Tim
On Fri, Nov 26, 2010 at 1:04 AM, Kapil Agrawal <kapil.agl at gmail.com> wrote:
> Just a quick clue that might help, try using multifilesrc ?
>
> On Thu, Nov 25, 2010 at 9:47 PM, Timothy Braun <braunsquared at gmail.com>wrote:
>
>> Hello Everyone,
>> I'm fairly new to G-Streamer so any input you can provide is much
>> appreciated. I'm working on a project where we need to generate a 2 minute
>> video which is a composite of a total of 24 input videos. The output video
>> will have 4 different 30 second sections, each containing a 3x2 grid of the
>> smaller input videos. The input videos are all naturally at 240x240 with
>> the goal of having a final output frame size of 720x480.
>>
>> Using gst-launch, I've been able to construct a sample 30 second clip
>> using a combination of inputs, videoboxes and a videomixer. Here is what
>> I've come up with so far:
>>
>> videomixer name=mix ! ffmpegcolorspace ! ffenc_mpeg1video ! ffmux_mpeg
>> name=mux ! queue ! filesink location=output.mpg
>> adder name=adder ! audioconvert ! ffenc_mp2 ! mux.
>> filesrc location=loop1.mp4 ! decodebin name=decode1
>> decode1. ! videobox border-alpha=0 top=-240 left=0 ! queue ! mix.
>> decode1. ! adder.
>> filesrc location=loop2.mp4 ! decodebin name=decode2
>> decode2. ! videobox border-alpha=0 top=-240 left=-240 ! queue ! mix.
>> decode2. ! adder.
>> filesrc location=loop3.mp4 ! decodebin name=decode3
>> decode3. ! videobox border-alpha=0 top=-240 left=-480 ! queue ! mix.
>> decode3. ! adder.
>> filesrc location=loop4.mp4 ! decodebin name=decode4
>> decode4. ! videobox border-alpha=0 top=0 left=0 ! queue ! mix.
>> decode4. ! adder.
>> filesrc location=loop5.mp4 ! decodebin name=decode5
>> decode5. ! videobox border-alpha=0 top=0 left=-240 ! queue ! mix.
>> decode5. ! adder.
>> filesrc location=loop6.mp4 ! decodebin name=decode6
>> decode6. ! videobox border-alpha=0 top=0 left=-480 ! queue ! mix.
>> decode6. ! adder.
>>
>> Now I need to do this 4 times, each time with a potentially different
>> video in each box. I've started looking into C interfaces as there's other
>> pieces of the puzzle which need to be tied into this, and I am trying to
>> determine the best way to tackle this. I originally was looking at Gnonlin,
>> but the documentation is lacking in regards to how gnloperations work. I
>> also recently stumbled upon the GES library by Edward Hervey, this looks
>> promising as well, but I haven't been able to spend much time on it.
>>
>> If I go the Gnonlin route, I believe I would need 6 compositions, one
>> for each box. At the 30 second marker, I would swap the filesource to a new
>> one using dynamic pads and listening for messages on the pipeline bus. Am I
>> far off on this? Any suggestions?
>>
>> As for the GES library, it looks very promising and powerful from the
>> little I read on it. Would this be the smarter route to take? If so, does
>> anyone have any suggestions for how the pipeline would be structured?
>>
>> Thank you in advance for your time on this and I truly appreciate any
>> information you are willing to share with me.
>>
>> Happy Thanksgiving,
>> Tim
>>
>>
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>
>
> --
> www.mediamagictechnologies.com (Gstreamer, ffmpeg, Red5, Streaming)
> twitter handle: @gst_kaps
> http://www.linkedin.com/in/kapilagrawal
>
>
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> Tap into the largest installed PC base & get more eyes on your game by
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