Some well known decoder wrongly set num_planes to 0 in their format instead of
one. In this case we would endup with no size when deciding buffer allocation.

All the element requires at least two buffers. This is not used for RW mode.

This should remove 1 copy between the decoder and the transform.

That pool may be different then the internal pool.

Implement a v4l2 element that wraps HW video converters.

In order to correctly set the pool min/max, we need to probe for CREATE_BUFS
ioctl. This can be done as soon as the format has been negotiated using a
count of 0.

Now that we might be copying out buffer (e.g. downstream don't support video
meta bug we need it) we need to move the EOS handling inside the process
method.

So far we where only setting saving the first plane stride in the meta. This was
leading to wrong values in GstVideoMeta.

As soon a the alpha component can be set, we can expose the RGB32 and BGR32
format as ARGB and BGRA as long we can deterministically set the alpha padding
value.

Correctly check if video meta is needed. In buffer pool, trust need_video_meta
flag in order to decide if configuration should succeed.

Fix stride request for tiled format and improve logging.

In certain cases we cannot live without video meta and/or crop meta
being enabled in our internal buffer pool. Ensure this is always the case,
regardless of having support for allocation query.

Upon error, the pools might not have been allocated yet, hence we should not
try and flush them (even though we still want to make sure the processing thread
is fully stopped).

Enforce pool being activate from before calling pool process. This should
help catching basic errors in the usage of buffer pool.

Buffer pool was guessing wrongly the number of planes rather
then reading the value from obj->n_v4l2_planes. This was causing
format YU12 (I420) to fail upon check.

The complex mechanic to try and choose the right thing did not work. Instead,
simply probe the non-contiguous format first and then the contiguous one.
This is in fact very low overhead, as there is a relatively small number of
pixel format supported by each devices.

The setup_format() was confusing since it does not set anything, in fact
it reads the setup from the driver and save it.

When the pipeline fails early, the pool might be unset before the processing
thread has run once. Add protection against that.

Certain decoder has been found to not choose a format automatically. Running
v4l2videodec on these would assert. This patch will make it fail cleanly
instead.

If caps are set again, we have a risk od returning from set_format with a
input_state pointing to dead memory. Clearing the pointer after unref fix
this issue.