I limit my High Def H.264 encoding to 8,000 Kbps per Apple Specs http://www.apple.com/quicktime/tutorials/h264.html This seems to be the sweet spot, for HD material, when balancing quality and file size. Any more Mbps and the file size increases but the quality stays the same. Any lower Mbps and the quality starts to suffer.
I am doing some quality tests and I've got to say that I can't tell a different between 8Mbps and 20Mbps. I can see a huge difference between single pass and multi pass but no difference between the different bit-rates.
Do you know if there are any benefits to encoding h.264 multi-pass at higher bit rates?
Do you know of any positive or negative speed differences when encoding at these different rates?
I totally agree with Craig, Apple's implementation of H.264 is near the bottom of the pile. I've recently competed a series of transcodes of high quality but complex sources using the x264 codec to 720p with an average datarate of 2.5Mbits/s, single pass. The quality is stunning.
A typical Apple movie trailer at 720p is 5.1Mb/s
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