anchorOnNextPacket

When true, the next packet sets lastSample to its own first sample index before decoding, so it is never gap-filled against an earlier position; the decoder then clears the flag. A stream starts this way: firmware 3.7.0 restarts the device counter at 0 on every STREAM_START, older firmware kept it running across STOP/START, and an anchored first packet is right for both. The cost: a loss inside the very first packet is not detectable.