Possibility that two different packets are combined together

[TheDaChicken]

In NRSC5, a PDU can contain incomplete packets that are meant to be combined together over time.

When dropped samples occur, it may be possible that a new incomplete packet combines with an old incomplete packet.

Is there anyway to prevent this?

[argilo]

To add some context, the partial packet (if any) at the end of a PDU is tracked in the pdu and pdu_idx members of the frame_t struct. It is meant to be combined with the partial packet at the start of the following PDU, but we may need to ensure that pdu and pdu_idx are reset any time a PDU is missed. The relevant code is here:

nrsc5/src/frame.c

Lines 622 to 642 in aa645c2

	if (j == 0 && hdr.pfirst)
	{
	unsigned int idx = st->pdu_idx[prog][hdr.stream_id];
	if (idx)
	{
	if (crc == 0)
	{
	memcpy(&st->pdu[prog][hdr.stream_id][idx], st->buffer + offset, cnt);
	output_push(st->input->output, st->pdu[prog][hdr.stream_id], cnt + idx, prog, hdr.stream_id, seq);
	}
	st->pdu_idx[prog][hdr.stream_id] = 0;
	}
	}
	else if (j == hdr.nop - 1 && hdr.plast)
	{
	if (crc == 0)
	{
	memcpy(st->pdu[prog][hdr.stream_id], st->buffer + offset, cnt);
	st->pdu_idx[prog][hdr.stream_id] = cnt;
	}
	}

[argilo]

I'm going to close this off now, since I believe it was fixed by #470. Let me know if that's not the case.