[FFmpeg-devel] [PATCH 4/5] lavc/qsvenc: add an option to set h264 pps for every frame

[Li, Zhong]

> From: ffmpeg-devel [mailto:ffmpeg-devel-bounces at ffmpeg.org] On Behalf
> Of Mark Thompson
> Sent: Wednesday, October 31, 2018 8:15 AM
> To: ffmpeg-devel at ffmpeg.org
> Subject: Re: [FFmpeg-devel] [PATCH 4/5] lavc/qsvenc: add an option to set
> h264 pps for every frame
> 
> On 30/10/18 09:21, Li, Zhong wrote:
> >> From: ffmpeg-devel [mailto:ffmpeg-devel-bounces at ffmpeg.org] On
> Behalf
> >> Of Moritz Barsnick
> >> Sent: Friday, October 26, 2018 7:49 PM
> >> To: FFmpeg development discussions and patches
> >> <ffmpeg-devel at ffmpeg.org>
> >> Subject: Re: [FFmpeg-devel] [PATCH 4/5] lavc/qsvenc: add an option to
> >> set
> >> h264 pps for every frame
> >>
> >> On Thu, Oct 25, 2018 at 20:36:10 +0800, Zhong Li wrote:
> >>> RepeatPPS is enabled by default in mfx. It is not necessary mostly
> >>> and wasting encoding bits.
> >>> Add an option to control it and disable it by default.
> >>
> >> Could this change in behavior surprise anyone? If it's okay to
> >> change, perhaps at least bump lavc's micro version?
> >>
> >> Moritz
> >
> > I doubt how many people would like to repeat every frame's pps.
> > Most codecs (x264/x265, and nvenc) won't do that by default.
> 
> Huh, right.  I feel like I must be missing something here - why would anyone
> ever want this option enabled?  It doesn't even help with seeking to
> arbitrary points in streams without global headers because you don't have
> the SPS as well.
> 
> If there isn't some hidden reason for this, it sounds fine to just switch it off
> completely without an option to reenable.

Two reasons I prefer to have an option to disable it:
1. Keep compatibility with previous behavior though the default case has been changed. 
  Since someone is surprised by current change as previous comment, would be a bigger surprise if totally disable it?
2. I am not very good at video streaming, but I guess in some rare cases of streaming, repeating pps maybe helpful
  (pps and sps can be transferred separated. Some pps are dropped won't cause the whole GOP can't decodable). 
  It is possible?