Add parent meta to compensated buffers

[JassonRM]

Adding parent meta to the compensated buffers avoided upstream bufferpools from trying to recycle the buffers before the memory was unreferenced. Solving issue #131.

[michaelgruner]

Thanks for the fix @JassonRM . However I don't understand how this fixes the original problem, the buffer is still not available, why isn't the pool allocating new buffers with this approach?

[JassonRM]

@michaelgruner the problem was because the original buffer was unreferenced but the underlying memory wasn't. So the bufferpool would try to recycle the buffer right away but fail due to the memory being used. Adding the parent meta the buffer is only recycled once all the child buffers have been unreferenced. And there is no need to allocate more since the bufferpool contains enough to keep recycling them after they stopped being used.

[michaelgruner]

This should also be true for RESTART_TIMESTAMP isn't it?

[JassonRM]

It is, I just added it. However, I was wondering why RESTART_TIMESTAMP never used gst_buffer_make_writable in the first place?

[michaelgruner]

It was an error, and it got past the reviews. Thanks for adding it.

[JassonRM]

Hi @michaelgruner @rrcarlosrodriguez, to remind you I don't have permission to merge this pull request.

[dzhang28]

I think there might be some side-effect could be introduced by this change.

The gst_buffer_ref would increase the refcount of given buffer. This could cause the gst_buffer_make_writable always return a copy of given buffer which in some case is unnecessary and might degrade peformance.