[FFmpeg-devel] Once again: Multithreaded H.264 decoding withffmpeg?

[John Kelley]

On Fri, May 30, 2008 at 2:55 AM, Robert Swain <robert.swain at gmail.com> wrote:
> Actually, levels correspond to VBV sizes, macroblocks per second,
> maximum MV lengths, etc., rather than codec features. :) Off the top
> of my head, level 4.1 is adequate for 1080p30 at somewhere around Blu
> Ray bit rates.

The 'problem' that most people run into with decoders that are
restricted to L4.1 is that most content on the internet today use lots
of reference frames and b-pyramid (which essentially counts as 2
reference frames) and the Decoded Picture Buffer for L4.1 limits you
to 4 refs at 1080P (2 if your use b-pyramid which then is essentially
useless) and 8 refs (IIRC) at 720P. Usually it's not a bitrate problem
as bitrate for L4.1 is sufficiently high.

 - John