[x264-devel] VBR

[Jason Garrett-Glaser]

On Thu, Sep 3, 2009 at 12:39 PM, aviad rozenhek<aviadr1 at gmail.com> wrote:
> Hi,
>
> For a video streaming application, I need to control bitrate to be under a
> threshold X for every window of T seconds, (X = target_bitrate * T)
> for instance, I require that every 5 seconds window will weigh no more than
> 5000mbits.
>
> I have been trying to achieve that by using VBV, setting
>   vbv-maxrate=target_bitrate
>     and
>  vbv-bufsize=target_bitrate * T
>
> is this the right approach?

Somewhat.  VBV is a leaky bucket buffering algorithm.

> on a related note, since we're encoding in realtime, and using 1pass ABR
> mode, I thought of developing a low-latency 2pass mode
> i.e. do the second pass with a 10 second delay to the first pass.

Impossible under x264's current design.

> this made sense to me because the input "movie" is infinite in size as it
> comes from camera that's always on.
> but is this similar to the new lookahead feature?

The new lookahead already does this, albeit quite differently.

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