From UVC jpeg webcam to OpenCV using Gstreamer

[Damien Picard]

Thank you !

2017-04-03 20:49 GMT+02:00 Thiago Sousa Santos <thiagossantos at gmail.com>:

>
>
> On Mon, Apr 3, 2017 at 11:14 AM, Damien Picard <picard.damien at gmail.com>
> wrote:
>
>> Hi,
>>
>> Due to an issue in opencv4tegra, I can not capture from my UVC webcam
>> using OpenCV. To get round this problem, I'm trying to use GStreamer and
>> its Python bindings to capture jpeg images from the webcam.
>>
>> To do that, I adapt this tutorial
>> <https://gist.githubusercontent.com/willpatera/7984486/raw/54b71f20b6a055839e44d59663ee4783042305cf/gst-appsink-opencv.py>
>> with a custom pipeline.
>> Currently my pipeline looks like this :
>>
>> v4l2src ! image/jpeg,width=1920,height=1080 ! jpegdec ! videoconvert !
>> appsink name=sink caps=video/x-raw, format=(string){BGR, GRAY8};
>> video/x-bayer,format=(string){rggb,bggr,grbg,gbrg}
>>
>> (The function that convert gstreamer to opencv array is exactly the same
>> as in the tutorial)
>>
>> It works (maybe the colors are not the good ones, but I'm not sure), but
>> I'm wondering if there is a way to retrieve the jpeg images directly from
>> gstreamer ? By this way, I will decode them using OpenCV and I hope that it
>> could, at least, limits processing.
>>
>
> Not sure if decoding inside opencv or in gstreamer itself makes any
> difference but yes you can have gstreamer pass the jpeg images to you.
>
> If you pay attention to your pipeline, it contains the 'jpegdec' element
> that is the one decoding jpegs into a raw format that later gets sent to
> appsink and into your application. So, you should just remove jpegdec and
> videoconvert and you will have jpeg images delivered directly to appsink.
> Remember to also remove the caps restrictions from appsink so it can accept
> jpeg input. Something like:
>
> v4l2src ! image/jpeg,width=1920,height=1080 ! appsink name=sink
>
> Hope this helps,
>
>
>>
>> Thank you in advance.
>>
>> --
>> Damien Picard
>> Expert GWT
>> <http://www.editions-eni.fr/livres/gwt-google-web-toolkit-developpez-des-applications-internet-riches-ria-en-java/.97a1a26e7d5be94763fc45ac2a1e961a.html>
>> Mob : 06 11 51 47 78
>>
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>>
>>
>
>
> --
> Thiago Sousa Santos
>
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>
>


-- 
Damien Picard
Expert GWT
<http://www.editions-eni.fr/livres/gwt-google-web-toolkit-developpez-des-applications-internet-riches-ria-en-java/.97a1a26e7d5be94763fc45ac2a1e961a.html>
Mob : 06 11 51 47 78
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