Re: [PATCH v3 2/9] add vnc h264 encoder

["Daniel P. Berrangé" <berrange@redhat.com>]

On Thu, Apr 24, 2025 at 12:39:22PM +0200, Dietmar Maurer wrote:
> > > +    g_object_set(
> > > +        vs->h264->gst_encoder,
> > > +        "tune", 4, /* zerolatency */
> > > +        /*
> > > +         * fix for zerolatency with novnc (without, noVNC displays
> > > +         * green stripes)
> > > +         */
> > > +        "threads", 1,
> > 
> > It seems a bit dubious for QEMU to workaround VNC client bugs, as our
> > server should be client agnostic. Shouldn't this flaw be fixed in noVNC
> > instead.
> 
> To be more specific, it is either a x264 encoder bug, or a web
> browser (VideoEncoder api) bug. You can reproduce it with noVNC.
> 
> Form what I found out, newer versions of x264 do not use the problematic mode at all (but we want to support older versions).

Do you have examples of versions which are fixed vs broken ? It would be
desirable to record something, so we know in future when we can potentially
remove the  workaround.

NB, QEMU only aims to support the 2 most recent releases of major distros,
so we don't need to care about arbitrarily old versions of x264

  https://www.qemu.org/docs/master/about/build-platforms.html

With regards,
Daniel
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