[x264-devel] A question about I-Frames and IDR-Frames

[Jason Martens]

On Sun, Nov 29, 2009 at 5:29 PM, Michael Fink
<michaelfink at jettenbach-net.de> wrote:

> On this mailing list and on doom9 I've found several threads in which the
> people are talking about I frames *and* IDR frames in h264. But I can't
> understand what they mean by an I frame in the context of h264?

    The spec calls an I frame an "I slice" if that's any help.

    An IDR (Instantaneous Decode Refresh) frame is an i-frame that
unsets reference to all previous frames.  The main point is that it's
directly seekable without the need to decode other frames.  The same
can not necessarily be said of regular i-frames, which may allow
subsequent frames to reference frames before it.

     The spec has a more detailed definition if you have questions.

--
Jason Martens
cacepi at gmail.com