Thanks for reporting your issue. Please make sure these boxes are checked before submitting your issue - thank you!

- [x] I looked for a similar issue and couldn't find any.
- [x] I tried with the latest version of GPAC. Installers available at http://gpac.io/downloads/gpac-nightly-builds/
- [x] I give enough information for contributors to reproduce my issue (meaningful title, github labels, platform and compiler, command-line ...). I can share files anonymously with this dropbox: https://www.mediafire.com/filedrop/filedrop_hosted.php?drop=eec9e058a9486fe4e99c33021481d9e1826ca9dbc242a6cfaab0fe95da5e5d95

I have created a couple of test uncompressed files with Y Cb Cr components (no subsampling). Converting those to PNG, JPEG or YUV fails with unable to convert caps.

A simple way to reproduce this is:

```
#gpac uncvg:c=Y,U,V:fps=0 -o gpac_yuv.heif
$ ../../gpac/bin/gcc/gpac -i gpac_yuv.heif -o out.yuv
No suitable filter to adapt caps between pid gpac_yuv.heif in filter uncvdec to filter writegen, disconnecting pid!
session last connect error Filter not found for the desired type
```

In addition, trying with PNG will segfault:
```
$ ../../gpac/bin/gcc/gpac -i gpac_yuv.heif -o out.png
No suitable filter to adapt caps between pid gpac_yuv.heif in filter uncvdec to filter encpng:1.6.37, disconnecting pid!
Segmentation fault (core dumped)
```

This doesn't appear to happen with other components - mono, mono+alpha planar, RGB pixel interleave, RGBA pixel interleave, and RGB planar appear OK.
uncompressed YCbCr can't be decoded to a file
This is a GitHub Issue
repo:gpac
owner:gpac
Title : uncompressed YCbCr can't be decoded to a file
Issue date:

--- start body ---
Thanks for reporting your issue. Please make sure these boxes are checked before submitting your issue - thank you!

- [x] I looked for a similar issue and couldn't find any.
- [x] I tried with the latest version of GPAC. Installers available at http://gpac.io/downloads/gpac-nightly-builds/
- [x] I give enough information for contributors to reproduce my issue (meaningful title, github labels, platform and compiler, command-line ...). I can share files anonymously with this dropbox: https://www.mediafire.com/filedrop/filedrop_hosted.php?drop=eec9e058a9486fe4e99c33021481d9e1826ca9dbc242a6cfaab0fe95da5e5d95

I have created a couple of test uncompressed files with Y Cb Cr components (no subsampling). Converting those to PNG, JPEG or YUV fails with unable to convert caps.

A simple way to reproduce this is:

```
#gpac uncvg:c=Y,U,V:fps=0 -o gpac_yuv.heif
$ ../../gpac/bin/gcc/gpac -i gpac_yuv.heif -o out.yuv
No suitable filter to adapt caps between pid gpac_yuv.heif in filter uncvdec to filter writegen, disconnecting pid!
session last connect error Filter not found for the desired type
```

In addition, trying with PNG will segfault:
```
$ ../../gpac/bin/gcc/gpac -i gpac_yuv.heif -o out.png
No suitable filter to adapt caps between pid gpac_yuv.heif in filter uncvdec to filter encpng:1.6.37, disconnecting pid!
Segmentation fault (core dumped)
```

This doesn't appear to happen with other components - mono, mono+alpha planar, RGB pixel interleave, RGBA pixel interleave, and RGB planar appear OK.
--- end body ---
