@grahamthompson - thanks for the explanation, it makes sense. One thing though, I don't remember this on my Sky box. I'm not a Sky advocate, and was very glad to get away from them, but would Sky be doing something different here? Or maybe I imagined it! Also, the skip back appears to be roughly 7 or 8 seconds on the HDR1000s, which seems a bit long if I'm understanding correctly what a GOP is...?
My Humax Forum » Freesat HD » HDR 1000, 1010, 1100S
"Instant Replay" Setting
(14 posts)-
| Fri 8 Mar 2013 11:35:28 #11 |
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souporjuice - 24 minutes ago »
@grahamthompson - thanks for the explanation, it makes sense. One thing though, I don't remember this on my Sky box. I'm not a Sky advocate, and was very glad to get away from them, but would Sky be doing something different here? Or maybe I imagined it! Also, the skip back appears to be roughly 7 or 8 seconds on the HDR1000s, which seems a bit long if I'm understanding correctly what a GOP is...?Does seem rather a long time. I would expect a GOP to be roughly 50-75 frames (2-3 seconds). It's hard to find exactly what settings the broadcasters mpeg encoders are using. The more frames you can pack into a GOP the greater the signal compression. Without mpeg compression digital TV simply wouldn't be practical (too much picture data).
For example 1920 x 1080 HD at 25 fps transmits 2073600 pixels/second purely for video. Each pixel has 24 bits of data, 8 each for Red Green and Blue giving a data requirement of 49766400 bits/second. Approx 50 Megabits/Second which is around 10 times the compressed stream actually uses.
It's possible the Sky boxes uses say a frame store buffer so the picture is delayed behind real time so when you pause you access a memory block with complete frames. This is merely speculation :-). Interesting to watch the same programme on two identical TV's side by one using Sky and the other Freesat
Need a broadcast engineer to really explain the complexities.
| Fri 8 Mar 2013 12:05:16 #12 | -
I think you might be right about Sky - I've noticed in the past a few seconds lag between a Sky TV and a terrestrial TV.
| Fri 8 Mar 2013 12:35:23 #13 | -
There are no complexities with my Panasonic TV it Buffers live TV, it isnt delayed in anyway and it certainly doesn't care about GOP, plug a HDD into it and it starts recording/buffering, it can then perfectly and instantly pause live TV and you can then catch up without ever losing the picture.
Just to make absolutely sure it was live I also had the sound from my 1000s coming through my amp which matched the sound on the TV's live picture.
So GOP has nothing to do with it, with my TV anyway.
Terrestrial and Satellite TV are always going to be a few seconds different, nothing unusual there.
| Fri 8 Mar 2013 12:57:12 #14 |
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