[x264-devel] Is it possible to dynamically change the quality mode using libx264

[Jason Garrett-Glaser]

On Mon, Oct 26, 2009 at 12:22 PM, declan harrison
<harrison.declan at googlemail.com> wrote:
>
>
> On Mon, Oct 26, 2009 at 7:02 PM, Jason Garrett-Glaser
> <darkshikari at gmail.com> wrote:
>>
>> On Mon, Oct 26, 2009 at 11:12 AM, declan harrison
>> <harrison.declan at googlemail.com> wrote:
>> > Hi
>> >
>> > Im using x264 with ffmpeg to encode videos on the fly (realtime with
>> > minimum
>> > buffering) in a proxy.  So I am working on a HTTP stream and therefore 1
>> > pass encoding is the only option available to me.
>> >
>> > My use case is that after encoding the video for say 10 seconds with a
>> > "--crf" value of 22 another network element informs me that I need to
>> > increase/decrease the quality of the video stream being sent to the
>> > client.
>> > I then would like to change the effective "crf" value that I am
>> > currently
>> > encoding the video stream.
>>
>> For streaming you need to set a maxrate and bufsize so that you don't
>> exceed the bounds of your connection.  If you want absolutely no
>> buffer whatsoever, i.e. zero-latency, you need to set bufsize =
>> (maxrate / framerate).
>>
>> x264 currently does not support reconfiguring ratecontrol in realtime,
>> but you can re-init the encoder if you want.
>>
>>
> Hi Jason
>
> So re-init the encoder will this cause many issues for the client or do you
> think that it will pass without much interference?

No issues for the client; the primary issue is that of tracking the
VBV buffer fullness so that you can init the encoder with the correct
initial occupancy for the VBV.

Dark Shikari