Transform plugin outbuf - plugin write problem

[张若]

Hi,

I am now writing a transform plugin for video stream.

When I use GstFlowReturn (*transform_ip) (GstBaseTransform *trans, GstBuffer *buf), it works fine. Inside the function I do nothing to the buffer. The ximagesink display is the camera capture.

Because of what I need is to change the buffer size, I come to GstFlowReturn (*transform) (GstBaseTransform *trans, GstBuffer *inbuf, GstBuffer *outbuf).

In this function, I first do a simple test with copying inbuf to outbuf. I check the data in outbuf which seems to be changed with camera captures. However, the ximagesink display is always black. I don't know why. It should be same to what I did in (*transform_ip), but not.

Thanks in advance!

Best regards

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[Nicolas Dufresne-5]

Le lundi 15 mai 2017 à 16:04 +0200, 张若 a écrit :

> When I use GstFlowReturn (*transform_ip) (GstBaseTransform *trans,
> GstBuffer *buf), it works fine. Inside the function I do nothing to
> the buffer. The ximagesink display is the camera capture.
>
> Because of what I need is to change the buffer size, I come
> to GstFlowReturn (*transform) (GstBaseTransform *trans, GstBuffer
> *inbuf, GstBuffer *outbuf).
> In this function, I first do a simple test with copying inbuf to
> outbuf. I check the data in outbuf which seems to be changed with
> camera captures. However, the ximagesink display is always black. I
> don't know why. It should be same to what I did in (*transform_ip),
> but not.

This is most likely a bug in your code, which isn't visible to us.

regards,
Nicolas
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[张若]

Actually, I just write based on the gsttransform.c/h in gst-template.

I only modify the part with transform_ip () to transform ().

In details:

1. Change the definition to:

    static GstFlowReturn gst_plugin_template_transform (GstBaseTransform * base, GstBuffer *inbuf,

    GstBuffer * outbuf);

2. Change class init to:

   GST_BASE_TRANSFORM_CLASS (klass)->transform =

      GST_DEBUG_FUNCPTR (gst_plugin_template_transform);

3. Change the main flow to:

    static GstFlowReturn

gst_plugin_template_transform (GstBaseTransform * base, GstBuffer *inbuf, GstBuffer * outbuf)

{

   GstMapInfo map_in; 

   GstMapInfo map_out;

   gst_buffer_map (inbuf, &map_in, GST_MAP_READ); 

   gst_buffer_map (outbuf, &map_out, GST_MAP_WRITE);

   gst_buffer_unmap (inbuf, &map_in);

   gst_buffer_unmap (outbuf, &map_out);

  return GST_FLOW_OK;

}

The other parts are remained. However, it only displays black, and when i check the outbuf, it has camera capture data.

Best regards,

Ruo

2017-05-15 16:48 GMT+02:00 Nicolas Dufresne <[hidden email]>:

Le lundi 15 mai 2017 à 16:04 +0200, 张若 a écrit :
> When I use GstFlowReturn (*transform_ip) (GstBaseTransform *trans,
> GstBuffer *buf), it works fine. Inside the function I do nothing to
> the buffer. The ximagesink display is the camera capture.
>
> Because of what I need is to change the buffer size, I come
> to GstFlowReturn (*transform) (GstBaseTransform *trans, GstBuffer
> *inbuf, GstBuffer *outbuf).
> In this function, I first do a simple test with copying inbuf to
> outbuf. I check the data in outbuf which seems to be changed with
> camera captures. However, the ximagesink display is always black. I
> don't know why. It should be same to what I did in (*transform_ip),
> but not.

This is most likely a bug in your code, which isn't visible to us.

regards,
Nicolas
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[张若]

In 3, I forget to put 1 line while writing the email:

gst_plugin_template_transform (GstBaseTransform * base, GstBuffer *inbuf, GstBuffer * outbuf)

{

   GstMapInfo map_in; 

   GstMapInfo map_out;

   gst_buffer_map (inbuf, &map_in, GST_MAP_READ); 

   gst_buffer_map (outbuf, &map_out, GST_MAP_WRITE);

   map_out.data = map_in.data;

   gst_buffer_unmap (inbuf, &map_in);

   gst_buffer_unmap (outbuf, &map_out);

  return GST_FLOW_OK;

}

2017-05-16 9:03 GMT+02:00 张若 <[hidden email]>:

Actually, I just write based on the gsttransform.c/h in gst-template.

I only modify the part with transform_ip () to transform ().

In details:

1. Change the definition to:

    static GstFlowReturn gst_plugin_template_transform (GstBaseTransform * base, GstBuffer *inbuf,

    GstBuffer * outbuf);

2. Change class init to:

   GST_BASE_TRANSFORM_CLASS (klass)->transform =

      GST_DEBUG_FUNCPTR (gst_plugin_template_transform);

3. Change the main flow to:

    static GstFlowReturn

gst_plugin_template_transform (GstBaseTransform * base, GstBuffer *inbuf, GstBuffer * outbuf)

{

   GstMapInfo map_in; 

   GstMapInfo map_out;

   gst_buffer_map (inbuf, &map_in, GST_MAP_READ); 

   gst_buffer_map (outbuf, &map_out, GST_MAP_WRITE);

   gst_buffer_unmap (inbuf, &map_in);

   gst_buffer_unmap (outbuf, &map_out);

  return GST_FLOW_OK;

}

The other parts are remained. However, it only displays black, and when i check the outbuf, it has camera capture data.

Best regards,

Ruo

2017-05-15 16:48 GMT+02:00 Nicolas Dufresne <[hidden email]>:

Le lundi 15 mai 2017 à 16:04 +0200, 张若 a écrit :
> When I use GstFlowReturn (*transform_ip) (GstBaseTransform *trans,
> GstBuffer *buf), it works fine. Inside the function I do nothing to
> the buffer. The ximagesink display is the camera capture.
>
> Because of what I need is to change the buffer size, I come
> to GstFlowReturn (*transform) (GstBaseTransform *trans, GstBuffer
> *inbuf, GstBuffer *outbuf).
> In this function, I first do a simple test with copying inbuf to
> outbuf. I check the data in outbuf which seems to be changed with
> camera captures. However, the ximagesink display is always black. I
> don't know why. It should be same to what I did in (*transform_ip),
> but not.

This is most likely a bug in your code, which isn't visible to us.

regards,
Nicolas

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[Yasushi SHOJI-2]

Hi,

On Tue, May 16, 2017 at 5:46 PM, 张若 <[hidden email]> wrote:
>
> In 3, I forget to put 1 line while writing the email:
> gst_plugin_template_transform (GstBaseTransform * base, GstBuffer *inbuf, GstBuffer * outbuf)
> {
>    GstMapInfo map_in;
>    GstMapInfo map_out;
>    gst_buffer_map (inbuf, &map_in, GST_MAP_READ);
>    gst_buffer_map (outbuf, &map_out, GST_MAP_WRITE);
>    map_out.data = map_in.data;

This won't work.  memcpy() it for test.  If you wanna play with GstBuffer and GstMemory, 

here is links:

https://gstreamer.freedesktop.org/data/doc/gstreamer/head/gstreamer/html/GstBuffer.html

https://gstreamer.freedesktop.org/data/doc/gstreamer/head/gstreamer/html/GstBuffer.html

>    gst_buffer_unmap (inbuf, &map_in);
>    gst_buffer_unmap (outbuf, &map_out);
>   return GST_FLOW_OK;
> }
-- 

            yashi

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