appsrc.SetProperty

Application Development
1

I’m trying to rewrite the example appsrc so I can build out the pipeline later, but I don’t think I’m doing it correctly as I get ERROR! couldn’t find Property. Please help me, so I can move on.

appsrc, err := gst.NewElement("appsrc")
if err != nil {
	return nil, err
}
videoInfo := video.NewInfo().WithFormat(video.FormatRGBA, width, height)
if err := appsrc.SetProperty("appsrc", videoInfo); err != nil {
	return nil, err
}
appsrc.SetProperty("callbacks", &app.SourceCallbacks{
    NeedDataFunc: func(self *app.Source, _ uint) {
        buffer := gst.NewBufferWithSize(videoInfo.Size())
        bytes := produceImageFrame()
        buffer.Map(gst.MapWrite).WriteData(bytes)
        buffer.Unmap()
        self.PushBuffer(buffer)
	},
})
2

There is no appsrc property in appsrc. I suspect you meant to set the caps property from the video info.

3

Exactly. Do you happen to know the correct name, or is this not the way to set the intended format?

4

@philn - by trial-and-error, this also doesn’t work

videoInfo := video.NewInfo().WithFormat(video.FormatRGBA, width, height)
if err := appsrc.Set("caps", videoInfo); err != nil {
    return nil, err
}

ERROR! invalid type gpointer for property caps

5

I would recommend using GstApp library API such as GstAppSrc.set_caps() instead.

6

Are suggesting Python instead of Go and the go-gst bindings?

7

Ah, sorry, no. I just picked the bindings that will look most like what it might look like in your case.

I assume go-gst has bindings for the the GstApp library from gst-plugins-base?

8

I assume go-gst has bindings for the the GstApp library from gst-plugins-base?

It does: app package - github.com/go-gst/go-gst/gst/app - Go Packages

Although heads up: some function signatures might change because I’m in the middle of reworking the bindings and generating them from the GIR files.

9

@ea7kir the caps property needs a GstCaps* as a value. The bound go type is the *gst.Caps object. You’ll need to call ToCaps() on the video info.

video package - github.com/go-gst/go-gst/gst/video - Go Packages Which wraps gst_video_info_to_caps

1 Like
10

Thank you @RSWillli, that part is now working, although I used .Set because there isn’t a .SetCaps function. Next problem is with setting gst.ClockTimeNone.

appsrc, err := gst.NewElement("appsrc")
if err != nil {
	fmt.Println("FAILED #1")
	return nil, err
}
videoInfo := video.NewInfo().WithFormat(video.FormatRGBA, width, height)
if err := appsrc.Set("caps", videoInfo.ToCaps()); err != nil {
	fmt.Println("FAILED #2")
	return nil, err
}
if err := appsrc.SetProperty("format", gst.ClockTimeNone); err != nil {
	fmt.Println("FAILED #3")
	return nil, err
}
if err := appsrc.SetProperty("callbacks", &app.SourceCallbacks{
	NeedDataFunc: func(self *app.Source, _ uint) {
		buffer := gst.NewBufferWithSize(videoInfo.Size())
		bytes := produceImageFrame()
		buffer.Map(gst.MapWrite).WriteData(bytes)
		buffer.Unmap()
		self.PushBuffer(buffer)
	},
}); err != nil {
	fmt.Println("FAILED #4")
	return nil, err
}

FAILED #3
ERROR! unable to perform type conversion: Type not implemented

11

To get started with a real world application, a few real world examples would help. So, after 3 weeks of getting nowhere, I have no choice but to abandon all hope and hand in the towel. I’m sorry, but Go was designed to be idiomatic - go-gst is not.