6 ms·

The vehicle transmitted MPEG4 video, that then had byte level corruption due to transmission issues. MPEG4 really doesn't like corruption.

• mrfusion 12y ago
  Ok so it was fine before transmission? But the article was talking about early blocks messing up the encoding on following blocks. I'm thinking if there are transmission errors it would be more like incorrect or flipped bits? Why would that affect encoding? Or is the transmission streaming, or is the receiver re-encoding it?
  • jreimers 12y ago
    The earlier blocks being corrupted would affect later blocks because the later blocks are encoded as the difference from the previous block, hence the error of the previous block propagates even if the later blocks are correct.
    • mrfusion 12y ago
      Ok, I get it now. Thanks jreimers and smackfu!
      • TheLoneWolfling 12y ago
        Jumping on this comment because HN won't allow me to respond to a prior comment of yours (link: https://news.ycombinator.com/item?id=7878923 https://news.ycombinator.com/item?id=7878923): > how can you have a current in a single wire without a loop? There are ions always wandering around in the ionosphere - the ionosphere is partly-ionized plasma. Low-density, but there. When you have a generator that produces an electric potential bias across the top/bottom of the craft, you end up with electrons being emitted into space from and positive ions being attracted to the side biased negative, and electrons in the ionosphere being attracted to the side biased positive. Effectively: the plasma completes the circuit. There are bunches of additional optimizations (electron guns, etc) but that's the basic idea.
        • mrfusion 12y ago
          Wow that makes sense. I thought the spacecraft would be above the atmosphere but maybes there are still a few ions in LEO? Also how could such a generator work? That makes a potential on the two ends?
          • TheLoneWolfling 12y ago
            There's a surprising amount of atmosphere up where we would consider it to be at orbital heights. People think of the atmosphere as suddenly ending, but it doesn't. For example, one of the major considerations for how the ISS orients its solar panels is minimizing drag. And that's what an electrical generator does. It produces an electric potential difference between its two terminals.
  • smackfu 12y ago
    > But the article was talking about early blocks messing up the encoding on following blocks. More accurate to say that it was messing up the decoding of following blocks.