Hi,
I want to extract the frame of a tiled mp4 using the Python API of GPAC, then process and render using OpenCV. Can you please tell me how to do it? I tried the custom_sink.py, but it throws errors. I also looked into this https://github.com/gpac/gpac/issues/1761 issue. 

When I ran the custom_sink.py on a tiled HEVC from Kvazaar, it ran and showed packets like this.
```
[  0   0   0  16   2   1 255  17 106  79 221  17 128 226 176 220   0   0
  15 120] (20,)
PCK Prop: 1280, 720

[  0   0   0  17   2   1  65 127  17 106  79 221  17 128 226 176 220   0
   0  15 120] (21,)
PCK Prop: 1280, 720

[  0   0   0  17   2   1  66 191  17 106  79 221  17 128 226 176 220   0
   0  15 120] (21,)
PCK Prop: 1280, 720

[  0   0   0  17   2   1  67 255  17 106  79 221  17 128 226 176 220   0
   0  15 120] (21,)
PCK Prop: 1280, 720

```
Can you tell me what these arrays imply? I guess these are frame data. But how can I make OpenCV read them?

But for tiled mp4 videos, it gives this error:
```
Exception ignored on calling ctypes callback function: <function filter_cbk_configure at 0x7f4f818325e0>
Traceback (most recent call last):
  File "/home/shubhamch/project/NetColab/env/lib/python3.8/site-packages/libgpac/libgpac.py", line 2725, in filter_cbk_configure
    filter = cast(obj, py_object).value
ValueError: PyObject is NULL
```

How to extract frames of tiled mp4 using Python API
This is a GitHub Issue
repo:gpac
owner:gpac
Title : How to extract frames of tiled mp4 using Python API
Issue date:

--- start body ---
Hi,
I want to extract the frame of a tiled mp4 using the Python API of GPAC, then process and render using OpenCV. Can you please tell me how to do it? I tried the custom_sink.py, but it throws errors. I also looked into this https://github.com/gpac/gpac/issues/1761 issue. 

When I ran the custom_sink.py on a tiled HEVC from Kvazaar, it ran and showed packets like this.
```
[  0   0   0  16   2   1 255  17 106  79 221  17 128 226 176 220   0   0
  15 120] (20,)
PCK Prop: 1280, 720

[  0   0   0  17   2   1  65 127  17 106  79 221  17 128 226 176 220   0
   0  15 120] (21,)
PCK Prop: 1280, 720

[  0   0   0  17   2   1  66 191  17 106  79 221  17 128 226 176 220   0
   0  15 120] (21,)
PCK Prop: 1280, 720

[  0   0   0  17   2   1  67 255  17 106  79 221  17 128 226 176 220   0
   0  15 120] (21,)
PCK Prop: 1280, 720

```
Can you tell me what these arrays imply? I guess these are frame data. But how can I make OpenCV read them?

But for tiled mp4 videos, it gives this error:
```
Exception ignored on calling ctypes callback function: <function filter_cbk_configure at 0x7f4f818325e0>
Traceback (most recent call last):
  File "/home/shubhamch/project/NetColab/env/lib/python3.8/site-packages/libgpac/libgpac.py", line 2725, in filter_cbk_configure
    filter = cast(obj, py_object).value
ValueError: PyObject is NULL
```

--- end body ---

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