Open darksidds opened 2 years ago
The caption meta is meant for storing CEA608/708 captions, not arbitrary strings. What kind of metadata is it that you're trying to store here?
You probably want to implement your own GstMeta
for this.
I'm trying to store an arbitrary string. Am I supposed to create a new implementation for GstMeta and call it something like NdiPerFrameMeta?
Yeah, or with GStreamer 1.20 you can also use the stringly-typed "custom meta" API.
However there's NDI metadata that maps directly to existing GstMeta
s, for example for closed captions.
Yeah, or with GStreamer 1.20 you can also use the stringly-typed "custom meta" API.
Unfortunatelly, GStreamer 1.20 is not out there yet. And probably it would be nice to have a dedicated class for ndi per-buffer metadata. How do you think?
However there's NDI metadata that maps directly to existing GstMetas, for example for closed captions.
Could you please clarify me a couple of things. I would appreciate that a lot:
If NDI metadata is mapped directly to existing GstMetas, then how do I access it in my c++ pipelines?
Let's say I have a GstBuffer
object, and I'm trying to iterate all GstMeta
objects stored in it. As it's shown below, I use gst_buffer_iterate_meta
function and compare gst_meta->info
with known gst_meta_get_info("SomeName")
or gotten directly from functions like gst_video_caption_meta_get_info()
. But if I don't know what implementation of GstMeta
to expect, then I can't access it or its fields. So, how do I do that?
while ((gst_meta = gst_buffer_iterate_meta(buffer, &state))) {
if (gst_meta->info == gst_video_caption_meta_get_info()) {
auto video_caption = (GstVideoCaptionMeta *) gst_meta;
// do stuff
} else if (gst_meta->info == gst_video_time_code_meta_get_info()) {
auto timecode_meta = (GstVideoTimeCodeMeta *) gst_meta;
// do stuff
} else if (gst_meta->info == gst_meta_get_info("GstNdiSrcMeta")) {
// do stuff
}
}
GstMeta
implentations? 1. If NDI metadata is mapped directly to existing GstMetas, then how do I access it in my c++ pipelines?
By using the relevant GStreamer APIs for those metas. I'm not sure I understand the question :)
2\. Let's say I have a `GstBuffer` object, and I'm trying to iterate all `GstMeta` objects stored in it. As it's shown below, I use `gst_buffer_iterate_meta` function and compare `gst_meta->info` with known `gst_meta_get_info("SomeName")` or gotten directly from functions like `gst_video_caption_meta_get_info()`. But if I don't know what implementation of `GstMeta` to expect, then I can't access it or its fields. So, how do I do that?
You have to know the meta for being able to access its fields. You need to call the corresponding C API or e.g. make use of the public struct definition from the C headers.
Is there a way to list all registered
GstMeta
implentations?
With some effort, yes. But you can't really do anything with them unless you explicitly know how to handle each.
I think there's some misunderstanding on your side how this API works and is supposed to be used. Maybe I can give some useful suggestion if we take a step back and you explain what exactly you're trying to do.
Tested under both Linux and Windows.