[x264-devel] Re: Slices in x264

[Jeff Clagg]

On Wed, Jan 17, 2007 at 10:59:11AM +0000, Ryan Dalzell wrote:
> On Tuesday 16 January 2007 22:57, Jeff Clagg wrote:
> > I don't have much to add beyond that Mans is right.
> >
> > From the most optimistic reckoning, using FEC at the transport stream
> > layer adds 8.5% overhead to EVERY PID IN THE STREAM; compare that to
> > using a few slices per frame, thus adding maybe 2% overhead in the
> > video stream only - which may be enough to add a satisfactory amount of
> > error resilience.
> 
> This is true, but the extra error resilience is only satisfactory because in 
> digital TV streams there is an I picture every half a second which will fix 
> up any accumulating errors. And I'd be certain that this regular I picture 
> adds a lot more than 8.5% to the video bitrate. In other applications it 
> would be cheaper and more effective to add FEC to the stream.

I agree that slices totally stink as a form of "error resiliance" in many
other applications. But there are many other common practices that are
useful for live digital TV but very useless for e.g. DVD-rip to disk.
I should probably have been more clear that they only seem reasonable
when you're talking about something like live digital TV over transport
stream. When you look at your menu of choices, multislice-per-frame
could easily end up making much more sense than Reed-Solomon FEC.

-- 
This is the x264-devel mailing-list
To unsubscribe, go to: http://developers.videolan.org/lists.html