[x264-devel] x264 level for 1080i content

[Weasel Friend]

Thank you so much for your response! Very helpful!

Do you know why levels 5.0, 5.1 and 5.2 do not allow interlaced encoding?
Maybe I overlooked it in the spec?

Thanks

On Thu, Jun 23, 2016 at 7:26 PM, BugMaster <BugMaster at narod.ru> wrote:

> On Thu, 23 Jun 2016 12:13:04 +0200, Weasel Friend wrote:
> > Hi,
>
> > today I tried to encode interlaced content with 1920x1080 and 4Mbps
> > and was wondering why x264 auto detects level 5.2 for it. When doing
> > the same settings but with progressive output the level is detected
> > as 5.0. As of my understanding DPB should not be affected by interlaced
> content?
>
> > x264 command I used:
> > x264 - --demuxer y4m --profile main --preset slow --bitrate 4000 --bff
> --output video.h264
>
> > Relevant output with --bff
> > y4m [info]: 1920x1080i 1:1 @ 2997/100 fps (cfr)
> > x264 [warning]: interlace + weightp is not implemented
> > x264 [warning]: interlaced (1) > level limit (0)
> > x264 [info]: profile Main, level 5.2
>
> > Relevant output without --bff
> > y4m [info]: 1920x1080p 1:1 @ 2997/100 fps (cfr)
> > x264 [info]: profile Main, level 5.0
>
> > I know I can restrict the level to 5.0 but I am curious if there
> > are any additional level requirements for interlaced content that I
> missed?
>
> > Thanks
>
> Hi. I am dunno if this can be counted as x264 bug. You should specify
> `--level 4.1` or `--ref 4` in this case. Here why it happens:
> 1) you use `--preset slow` which have default ref=5;
> 2) you didn't specified `--level` so x264 do NOT try to reduce ref
> count (because it doesn't know to which level);
> 3) x264 tries to find level that allow specifed DPB (with ref=5) but
> because levels from 1.0 to 4.2 don't allow such DPB we skip them;
> 4) but we skip levels from 5.0 to 5.1 too because the last level that
> allowed interlaced encoding was level 4.1;
> 5) so we stop at level 5.2 because it is the last one we check and we
> need to specify some level anyway (even thou level 5.2 also doesn't
> allow interlaced encoding).
>
> _______________________________________________
> x264-devel mailing list
> x264-devel at videolan.org
> https://mailman.videolan.org/listinfo/x264-devel
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.videolan.org/pipermail/x264-devel/attachments/20160623/c279f9bd/attachment.html>