问题
I'm working on a kind of rich remote desktop system, with a video stream of the desktop encoded using avcodec/x264. I have to set manually the GOP size for the stream, and so far I was using a size of fps/2. But I've just read the following on Wikipedia:
This structure [Group Of Picture@ suggests a problem because the fourth frame (a P-frame) is needed in order to predict the second and the third (B-frames). So we need to transmit the P-frame before the B-frames and it will delay the transmission (it will be necessary to keep the P-frame).
It means I'm creating a lot of latency since the client needs to receive at least half of the GOP to output the first frame following the I frame. What is the best strategy for the GOP size if I want the smallest latency possible ? A gop of 1 picture ?
回答1:
If you want to minimize latency with h264, you should generally avoid b-frames. This way the decoder has at least a chance to emit decoded frames early. This prevents decoder-induced latency.
You may also want to tune the encoder for latency, by reducing/disabling look-ahead. x264 has a "zero-latency" setting which should be a good starting point for finding you optimal settings.
The "GOP" size (which afaik is not really defined for h264; I'll just assume you mean the I(DR)-frame interval) does not necessarily affect the latency. This parameter only affects how long a client will have to wait until it can "sync" on the stream (time-to-first-picture).
来源：https://stackoverflow.com/questions/41523234/gop-size-for-realtime-video-stream