Returns the frames in packet which overlap the given range, or returns std::nullopt if there is

no overlap. The intersection is guaranteed to start and end on a frame boundary. That is, for

every non-nullopt result, start = packet.start*k for some non-negative integer k.

The intersection is never larger than the packet or the range. That is, for every non-nullopt

result, length

<

= min(packet.length, range_length). For example:

IntersectPacket(packet = {.start = 0.0, .length = 10},

range_start = 1,

range_length = 2);

returns:

.start = 1.0

.length = 2

.payload = packet.payload + 1 frame

When the range starts or ends on a fractional frame, the intersection is shifted to include

complete frames. The intersection starts with the packet's first frame that overlaps the range.

For example:

IntersectPacket(packet = {.start = 0.0, .length = 10},

range_start = 1.5,

range_length = 2);

returns:

.start = 1.0

.length = 2

.payload = packet.payload + 1 frame

The packet may start on a fractional frame position. For example:

IntersectPacket(packet = {.start = 0.9, .length = 10},

range_start = 2.5,

range_length = 3);

returns:

.start = 1.9

.length = 3

.payload = packet.payload + 1 frame