a77 video bitrate at 1080p 60fps 28mbps

Started Sep 4, 2011 | Discussions thread
Kenneth Daves
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Re: a77 video bitrate at 1080p 60fps 28mbps
In reply to Spazmedia, Sep 8, 2011

Spazmedia wrote:

To put it into perspective at the maximum bitrate for the a77, each frame has a size of approx 60 KB while an uncompressed 1080p frame with 8 bits per channel is about 6 MB ...

Those looking to new line of Sony cameras to do 1080p at 60fps I fear will be a bit dissapointed. Even their new large sensor pro video camera, the NEXFS100,
uses the same codec.

How did you arrive at an "average" frame size of 60KB? Did you divide the megabits per second data rate by the frames per second? As I am sure you know, neither Mpeg 4 nor AVCHD work that way. Instead they compress video by creating a series of I frames (the entire frame is highly compressed) each of which is followed by a series of B (bi-directional) and P (predictive) frames that essentially record only changes from frame to frame. The claim is that AVCHD compression algorithms are more "efficient" than mpeg 4 so that the data rate can be lower and still result in comparable video quality when decompressed for playback or editing. I haven't seen any tests that prove otherwise.

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Ken Daves

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