Querying framerate in Python

[joseph]

I'm trying to query the framerate from a simple Python gstreamer script and
seeing the following error

TypeError: unknown type GstFraction

I'm getting the same error on Ubuntu and Mac.  Here is the code snippet
attempting to get the framerate


    def get_frame_res(self, sample):
        caps_format = sample.get_caps().get_structure(0)
        frmt_str = caps_format.get_value('format')
        video_format = GstVideo.VideoFormat.from_string(frmt_str)
        width = caps_format.get_value('width')
        height = caps_format.get_value('height')
        fps = caps_format.get_value('framerate')
        return width, height, fps


The above method is called from my on_buffer method when I receive the first
sample

def on_buffer(self, sink: GstApp.AppSink, data: typ.Any) -> Gst.FlowReturn:
        sample = sink.emit("pull-sample")
        if self.frame_num == 0:
            w, h, fps = self.get_frame_res(sample)
            print("width::height::fps == {}:{}".format(w,h,fps))

I have read through a lot of posts about installing the correct version of
python-gst but nothing was able to allow me to get past the TypeError for
GstFraction
(ex. sudo apt-get install python-gst-1.0)



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[Thibault Saunier-4]

Hello,

There is clearly something wrong with your gst-python installation. What does `print(Gst.Fraction)` do? It should print:                                                                                                                              `<class 'gi.overrides.Gst.Fraction>`

- Thibault

On Tue, Jul 21, 2020 at 6:38 PM joseph <[hidden email]> wrote:

I'm trying to query the framerate from a simple Python gstreamer script and
seeing the following error

TypeError: unknown type GstFraction

I'm getting the same error on Ubuntu and Mac.  Here is the code snippet
attempting to get the framerate


    def get_frame_res(self, sample):
        caps_format = sample.get_caps().get_structure(0)
        frmt_str = caps_format.get_value('format')
        video_format = GstVideo.VideoFormat.from_string(frmt_str)
        width = caps_format.get_value('width')
        height = caps_format.get_value('height')
        fps = caps_format.get_value('framerate')
        return width, height, fps


The above method is called from my on_buffer method when I receive the first
sample

def on_buffer(self, sink: GstApp.AppSink, data: typ.Any) -> Gst.FlowReturn:
        sample = sink.emit("pull-sample")
        if self.frame_num == 0:
            w, h, fps = self.get_frame_res(sample)
            print("width::height::fps == {}:{}".format(w,h,fps))

I have read through a lot of posts about installing the correct version of
python-gst but nothing was able to allow me to get past the TypeError for
GstFraction
(ex. sudo apt-get install python-gst-1.0)



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[joseph]

It seems to be able to support Gst.Fraction.

I get the following output ... I also included the snippet

$ python run_appsink.py
GSTSample - constructor
width == 640
height == 480
<class 'gi.repository.Gst.Fraction'>
An exception occurred
Exception ignored in: <module 'threading' from
'/Users/josephceli/.pyenv/versions/3.6.1/lib/python3.6/threading.py'>
Traceback (most recent call last):
  File "/Users/josephceli/.pyenv/versions/3.6.1/lib/python3.6/threading.py",
line 1296, in _shutdown
    _main_thread._delete()
  File "/Users/josephceli/.pyenv/versions/3.6.1/lib/python3.6/threading.py",
line 1015, in _delete
    del _active[get_ident()]
KeyError: 123145386319872

-----------------------------------------------------------------------------------------------

def get_frame_res(self, sample):
        caps_format = sample.get_caps().get_structure(0)
        frmt_str = caps_format.get_value('format')
        video_format = GstVideo.VideoFormat.from_string(frmt_str)
        width = caps_format.get_value('width')
        print("width == {}".format(width))
        height = caps_format.get_value('height')
        print("height == {}".format(height))
        print(Gst.Fraction)
        try:
            fps = caps_format.get_value('framerate')
            print("fps == {}".format(fps))
        except:
            print("An exception occurred")
        sys.exit()
        return width, height, fps



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[joseph]

I figured it out.

I should be using

fps_fraction = caps_format.get_fraction('framerate')

instead of get_value

Thank you for your help.

Joseph



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