[Discuss-gnuradio] qa_atsc.py type question

Hello everyone,

I have a question regarding a few lines in qa_atsc.py .

In test_loopback_000, we have:
src = vector_source_ts(src_data)
rand = atsc.randomizer()
and skipping a few lines:
self.tb.connect(src, rand, derand, dst)

The definition of vector_source_ts:

class vector_source_ts(gr.hier_block2):
"""
MPEG Transport stream source for testing.
"""
def __init__(self, ts):
"""
Pad tranport stream packets to 256 bytes and reformat appropriately.

@param ts: MPEG transport stream.
@type ts: sequence of ints in [0,255]; len(ts) % 188 == 0
"""

src = gr.vector_source_b(pad_transport_stream(ts))
s2v = gr.stream_to_vector(gr.sizeof_char,
atsc.sizeof_atsc_mpeg_packet)

gr.hier_block2.__init__(self, "vector_source_ts",
gr.io_signature(0, 0, 0),
s2v.output_signature())
self.connect(src, s2v, self)

=================================
It is clear that in "src = vector_source_ts(src_data)",
src_data is a tuple of integers, and src is a gnuradio_vector datatype
with elements guradio_characters and each vector length is
atsc.sizeof_atsc_mpeg_packet

That is, "src = vector_source_ts(src_data)" does *not* create any
atsc_mpeg_packet type data, as required by atsc_randomizer.

In other words, I am claiming that in test_loopback_000() of qa_atsc.py,
the input to atsc.randomizer() is *not* atsc_mpeg_packet, but rather a
gnuradio_vector data type. Notice that no special atsc.pad() is being run
(which converts a gnuradio_vector/stream(?) into an atsc_mpeg_packet).

I originally believed some casting was being done, but atsc_mpeg_packet is
not easy to convert to and fro, it contains numerous data arrays, and
variables.

Can someone please explain the input/output datatypes in
test_loopback_000() in qa_atsc.py?

Thanks very much,
Jonathan

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