6 ms·

How much bandwidth would that require at 1080p with compression? Well, if we assume 16:1 compression ratio, that's 1920x1080x3/(16x1024) KB per frame, times 24

How much bandwidth would that require at 1080p with compression? Well, if we assume 16:1 compression ratio, that's 1920x1080x3/(16x1024) KB per frame, times 24 fps = 9.11MB per second. So a 73Mbit wifi connection would be required. Can the RPi push that? 30fps would require a 90MBit link.

tlarkworthy 13y ago
very unlikely
sjwright 13y ago
Or perhaps we could assume a 32:1 compression ratio on 720p content -- that's about 10 megabits per second. I don't know if the Pi could even do that with sufficiently low latency (the server's specs will probably be more important anyway) but if we're going to give a flea computer a task, at least make it vaguely feasible. And when did wifi suddenly become a requirement? And where did you get 24 fps for gaming?
- sillysaurus2 13y ago
  24fps is movie framerates. It's the lowest fps which humans find tolerable. 16:1 compression ratio is based on DXT compression, which looks like ass, but is able to be done in realtime if the server is beefy enough. 8:1 would be better. 32:1 would look so terrible that I'm not sure anyone would be willing to sit through it. Wifi is a requirement to make it go mainstream. Most people aren't willing to run physical cable through their living spaces, either due to lack of patience or equipment.
  - sliverstorm 13y ago
    Powerline is almost there.
  - Dylan16807 13y ago
    DXT is extremely lightweight compression designed to be decompressed in parallel during the rendering process. 10mbps is plenty if you're using a video codec, and the Pi has hardware H.264 support.
    - nitrogen 13y ago
      H.264 imposes a few seconds of lag to get to that sort of compression ratio with acceptable quality. Good for movies, not so good for games.
      - Dylan16807 13y ago
        Are you sure about that? As I understand it you usually don't want to have more than 4-5 B-frames in a row. And if you use baseline profile you eliminate B-frames and can cut the latency to be less than a frame. See also: http://www.eetimes.com/document.asp?doc_id=1273759 http://www.eetimes.com/document.asp?doc_id=1273759 http://x264dev.multimedia.cx/archives/249 http://x264dev.multimedia.cx/archives/249
      - deleted 13y ago
        [deleted]
  - comex 13y ago
    Why does it need to be a texture compression algorithm? Intel Quick Sync can encode H.264 with pretty low latency.
  - web007 13y ago
    YouTube can stream from outside of my WiFi network at 720p or 1080p, streaming within it shouldn't be a problem. Pushing the codec pieces far enough down the stack that they're done by hardware will be the bottleneck. In any case, http://steamcommunity.com/groups/homestream http://steamcommunity.com/groups/homestream seems to answer this - they're going to build it.
  - jcampbell1 13y ago
    I am confused by your calculations. What does texture compression have to do with video compression? A peak 5 mbps h264 video with no B frames would look very good and have no latency.
- sliverstorm 13y ago
  The Pi will choke. It's LAN adapter is on the USB bus, and peak real-world throughput was something like 1-2Mbps. Normally not a problem with prerendered video, because they have high compression ratios, but live streaming can't offer the same level of compression.
noselasd 13y ago
netcat piping to /dev/null on an RPI saturates the 100Mbit NIC on my RPI but with over 70% cpu load, on my non-scientifc tests.
newman314 13y ago
I wouldn't attempt wifi. My house is full GigE. I haven't played much with the Pi as yet so no idea as to what kind of throughput is possible. But regardless, I'm happy to use a beefier client if that is what is required. Noticed I said Pi or Mac. Maybe a Mini would be more suited to this.

tlarkworthy 13y ago

very unlikely

sjwright 13y ago

Or perhaps we could assume a 32:1 compression ratio on 720p content -- that's about 10 megabits per second. I don't know if the Pi could even do that with sufficiently low latency (the server's specs will probably be more important anyway) but if we're going to give a flea computer a task, at least make it vaguely feasible. And when did wifi suddenly become a requirement? And where did you get 24 fps for gaming?

sillysaurus2 13y ago
24fps is movie framerates. It's the lowest fps which humans find tolerable. 16:1 compression ratio is based on DXT compression, which looks like ass, but is able to be done in realtime if the server is beefy enough. 8:1 would be better. 32:1 would look so terrible that I'm not sure anyone would be willing to sit through it. Wifi is a requirement to make it go mainstream. Most people aren't willing to run physical cable through their living spaces, either due to lack of patience or equipment.
- sliverstorm 13y ago
  Powerline is almost there.
- Dylan16807 13y ago
  DXT is extremely lightweight compression designed to be decompressed in parallel during the rendering process. 10mbps is plenty if you're using a video codec, and the Pi has hardware H.264 support.
  - nitrogen 13y ago
    H.264 imposes a few seconds of lag to get to that sort of compression ratio with acceptable quality. Good for movies, not so good for games.
    - Dylan16807 13y ago
      Are you sure about that? As I understand it you usually don't want to have more than 4-5 B-frames in a row. And if you use baseline profile you eliminate B-frames and can cut the latency to be less than a frame. See also: http://www.eetimes.com/document.asp?doc_id=1273759 http://www.eetimes.com/document.asp?doc_id=1273759 http://x264dev.multimedia.cx/archives/249 http://x264dev.multimedia.cx/archives/249
    - deleted 13y ago
      [deleted]
- comex 13y ago
  Why does it need to be a texture compression algorithm? Intel Quick Sync can encode H.264 with pretty low latency.
- web007 13y ago
  YouTube can stream from outside of my WiFi network at 720p or 1080p, streaming within it shouldn't be a problem. Pushing the codec pieces far enough down the stack that they're done by hardware will be the bottleneck. In any case, http://steamcommunity.com/groups/homestream http://steamcommunity.com/groups/homestream seems to answer this - they're going to build it.
- jcampbell1 13y ago
  I am confused by your calculations. What does texture compression have to do with video compression? A peak 5 mbps h264 video with no B frames would look very good and have no latency.
sliverstorm 13y ago
The Pi will choke. It's LAN adapter is on the USB bus, and peak real-world throughput was something like 1-2Mbps. Normally not a problem with prerendered video, because they have high compression ratios, but live streaming can't offer the same level of compression.

noselasd 13y ago

netcat piping to /dev/null on an RPI saturates the 100Mbit NIC on my RPI but with over 70% cpu load, on my non-scientifc tests.

newman314 13y ago

I wouldn't attempt wifi. My house is full GigE. I haven't played much with the Pi as yet so no idea as to what kind of throughput is possible. But regardless, I'm happy to use a beefier client if that is what is required. Noticed I said Pi or Mac. Maybe a Mini would be more suited to this.