[x264-devel] x264 Development Newsletter: Vol. 28

[Alex Giladi]

On Thu, Apr 5, 2012 at 7:24 AM, aviad rozenhek <aviadr1 at gmail.com> wrote:
> On Wed, Apr 4, 2012 at 20:30, Jason Garrett-Glaser <jason at x264.com> wrote:
>>
...
>> > 3. adaptive bitrate has become very important, and with it, synchronized
>> > GOPs across encodes in different bitrates.
>> > this is currently supported in x264 by using fixed sized GOPs. what are
>> > your
>> > thoughts regarding a more content-aware approach?
>>
>> x264 supports this with adaptive GOP too; all encodes with the same
>> lookahead settings and the same source will give the same distribution
>> of frame types, no matter what the bitrate.
>
>
> that's very interesting, I didn't know that.
> I guess it only works when encoding to the same resolution, though ...
> would it make sense to encode to one resolution [lets call it the master
> resolution] using adaptive GOP settings, and then encode all other
> bitrates/resolutions using the GOP boundaries of the master resolution?
>
You can "borrow" the frame types (either programmatically, or using
the stats file) and reuse either IDR's or all frame types.
You end up having essentially a 2-pass encode, with one "master", and
N-1 "slaves", and all N have same segmentation properties.