Is anyone else getting this? Only seems to happen on SD channels? Audio keeps going but the picture is stuck on the frame when hitting the skip forward. Sometimes it starts playing again after a few seconds other times you have to skip back and forward a couple of times to make it unfreeze. I'm using LAV filters.
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The more comments I read, the more I think this issue is independent of software. Even largely independent of codec and splitter. The biggest factor is the head-end encoder.
To a large extent codecs and splitters are "mechanical". Feed in X; get out Y.
My understanding is that codecs aren't able to fully decode frames until they hit the start of a new GOP (group of pictures). Now, I know that is not entirely accurate for h.264 which doesn't have to have closed GOPs, but the principle still applies - codecs wait until they have enough context before turning on their output. Otherwise they'd output... garbage. Some codecs may require slightly less context than others due to their internal design... however there are still non-negotiables.
If you encode a stream with short GOPs and lots of safe entry points and/or I frames then the codec can build up the required context and turn on the output quickly. If you encode a stream with longer GOPs and few safe entry points and/or I frames (more complex inter frame references) then the codec takes longer to get its context and turn on the output.
The first case takes more bits than the second for the same picture quality. We know that Freeview is running at capacity. With the addition of Sommet I suspect Kordia is fine-tuning to try and steal as many bits as possible for Sommet while maintaining the picture quality of the other channels in the mux as best as possible. Stealing bits always has a cost!
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