On 2022-08-14 20:57, Nikos Balkanas wrote:
Aaaah, it's the dreaded max_samps_per_buffer:(
Yup, you need to make your read buffer aligned to max_samps_per_buffer...
HTH
Nikos
I'll note that rx_samples_to_file uses:
std::vector<samp_type> buff(samps_per_buff);
For its buffer. I don't know whether std::vector arranges for alignment.
On Sun, Aug 14, 2022 at 9:24 PM <wozn...@gmail.com> wrote:
Nikos,
Thanks for the reply. I traced it to the “recv” call which has left me puzzled.
I added a bunch of instrumentation to see if I was walking off the end of my
memory that was allocated to the 16-bit I/Q buffer.
const std::int32_t startIndex = 2*num_accum_samps;
const std::int32_t remainingSize = 2*sampleLength-(2*num_accum_samps);
std::cout << "iq[" << startIndex << "] = " << iq[startIndex];
std::cout << "\t" << remainingSize;
std::cout << "\t" << startIndex + remainingSize;
std::cout << "\t" << bufferSize << std::endl;
num_accum_samps += rx_stream->recv(&iq[startIndex], remainingSize, meta, 5.0,
true);
And I can get it to faithfully crash every single time when I don’t pad my
array of 16-bit integers by an additional 2165 int16s. I included some output
indicating where I’ve specified as the start of the buffer for it to write to,
followed by the remaining size, followed by the sum of the two just to make
sure I can math, and finally the actual reserved buffer size plus the pad of
2164 int16s.
…
iq[1180480] = 0 19520 1200000 1202164
iq[1185920] = 0 14080 1200000 1202164
iq[1191360] = 0 8640 1200000 1202164
iq[1196800] = 0 3200 1200000 1202164
Segmentation fault (core dumped)
If you’ll notice, I’ve specified for it to start at index 1196800 and that the
number of samples per buffer being passed to recv() is 3200. I think I’m just
being dense / misinterpreting the nsamps_per_buff (the second parameter of the
“recv” call) because it seems as if it is not respecting the remaining buffer
size that I am specifying and attempting to write beyond the bounds of the
memory I’ve allocated for the buffer.
Is there some alignment or minimum buffer size that I’m not aware of?
Thanks,
Chris
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