On Fri, 24 Feb 2017, Christophe de Dinechin wrote:
[...]
> Looking at the patch, I wonder why we pass an offset and a stride from
> different sources (offset is from the source, but stride is from the
> bitmap)? Shouldnʼt we use the stream stride?
I think that's correct:
* bitmap->{x,y} are the width and height of the source image.
* bitmap->stride is the size in bytes of each line. In other words
that's how much you must add to the pointer to get the pixel of the
next line.
* src->{left,right,top,bottom} identifies which subset of the source
image should be encoded and sent to the client. So the offset
corresponds to the src->left.
However I don't see any way to tell gst_buffer_add_video_meta_full()
that you only want to take 400 pixels out of every 640 pixel line, or
only 200 lines out of the 480 lines.
For instance if we have
bitmap->x = 640
bitmap->y = 480
bitmap->stride = 2560
src->left = src->top = 0
src->right = 200
src->bottom = 100
Then we will call:
gst_buffer_add_video_meta_full(buffer, GST_VIDEO_FRAME_FLAG_NONE,
encoder->format->gst_format,
640 /* bitmap->x */, 480 /* bitmap->y */,
1,
{ 0 } /* offset */,
{ 2560 } /* stride */);
How will GStreamer know that it should encode a 200x100 video since we
did not tell it that:
src->right - src->left = 200
src>bottom - src->top = 100
(not that any of this explains why it does not work for me since in my
case src->right-src->left==bitmap->x and src->bottom-src->top==bitmap->y)
--
Francois Gouget <fgouget@xxxxxxxxxxxxxxx>_______________________________________________
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