This function fills info with the GstMapInfo of length merged memory blocks
starting at idx in buffer. When length is -1, all memory blocks starting
from idx are merged and mapped.
flags describe the desired access of the memory. When flags is
GST_MAP_WRITE, buffer should be writable (as returned from
gst_buffer_is_writable()).
When buffer is writable but the memory isn't, a writable copy will
automatically be created and returned. The readonly copy of the buffer memory
will then also be replaced with this writable copy.
The memory in info should be unmapped with gst_buffer_unmap() after usage.
This function fills info with the GstMapInfo of length merged memory blocks starting at idx in buffer. When length is -1, all memory blocks starting from idx are merged and mapped. flags describe the desired access of the memory. When flags is GST_MAP_WRITE, buffer should be writable (as returned from gst_buffer_is_writable()). When buffer is writable but the memory isn't, a writable copy will automatically be created and returned. The readonly copy of the buffer memory will then also be replaced with this writable copy. The memory in info should be unmapped with gst_buffer_unmap() after usage.