# Set\_region issue

**URL:** <https://aravis-project.discourse.group/t/set-region-issue/318>\
**Category:** Using Aravis\
**Created:** [August 31, 2021, 3:36pm UTC](https://aravis-project.discourse.group/t/set-region-issue/318 "2021-08-31T15:36:18Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![drmcnelson](https://yyz2.discourse-cdn.com/free1/user_avatar/aravis-project.discourse.group/drmcnelson/32/112_2.png) [@drmcnelson](https://aravis-project.discourse.group/u/drmcnelson)\
**Post date:** [August 31, 2021, 3:36pm UTC](https://aravis-project.discourse.group/t/set-region-issue/318/1 "2021-08-31T15:36:18Z")

</div>

Hi

The call `set_region()` fails (or at least, for my firefly) when either x0 or y0 is not 0.

```auto
print( 'setting roi', x0, y0, width, height )
self.cam.set_region(x0, y0, width, height)

```

Produces:

```auto
setting roi 50 100 100 100
set roi arv-device-error-quark: USB3Vision write_memory error (invalid-parameter) (5)

```

A subesequent call to get\_region() produces:

```auto
region of interest (x=0, y=0, width=720, height=540) stream buffers 100

```

---

<div class="post-metadata">

**Author:** ![Emmanuel](https://yyz2.discourse-cdn.com/free1/user_avatar/aravis-project.discourse.group/emmanuel/32/198_2.png) [@Emmanuel](https://aravis-project.discourse.group/u/Emmanuel)\
**Post date:** [September 1, 2021, 6:40am UTC](https://aravis-project.discourse.group/t/set-region-issue/318/2 "2021-09-01T06:40:07Z")

</div>

Hi,

Please create a new topic if you have a new question. Also take care to correctly format your messages, it makes them easier to read.

Back to your question: when you have this sort of issues, you can first try to enable the Aravis debug output. You just have to set the `ARV_DEBUG` environment variable:

```bash
export ARV_DEBUG=all

```

or:

```auto
ARV_DEBUG=all ./your_code

```

What is the debug output when debug is enabled ?