Packet encoder, qam, program jammed up

I’m trying to take an input file, encode it as qam and dump it to a wav
file.
You know, one of those simple things students do for no reason.

Well, when I try it without a packet_mod_b, the output I get from
my decoder is all 0s, I’m not sure what I expected to happen
without synchronizers, but it doesn’t work. Heh. But that’s
just background.

When I put a packet_mod_b in there, the program freezes and never
only outputs the first 100k of the output wave (buffers
presumably). I think it’s maybe 40k short. I end up hitting ^C
after a while…

Why is it freezing up on me?

[The code below is generated by GRC.]

##################################################
  excess_bw=0.35,
)
self.connect((self.gr_sig_source_x_0, 0), (self.gr_multiply_xx_0, 1))
self.connect((self.digital_qam_mod_1, 0), (self.gr_multiply_xx_0, 0))
self.connect((self.gr_file_source_0, 0), (self.blks2_packet_encoder_0, 0))
self.connect((self.blks2_packet_encoder_0, 0), (self.digital_qam_mod_1, 0))


If riding in an airplane is flying, then riding in a boat is swimming.
116 jumps, 48.6 minutes of freefall, 92.9 freefall miles.