[FFmpeg-devel] [PATCH 1/7] lavc/libopenh264enc: Add default qmin/qmax support

[Fu, Linjie]

> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of
> James Almer
> Sent: Tuesday, March 31, 2020 23:44
> To: ffmpeg-devel at ffmpeg.org
> Subject: Re: [FFmpeg-devel] [PATCH 1/7] lavc/libopenh264enc: Add default
> qmin/qmax support
> 
> On 3/31/2020 12:31 PM, Linjie Fu wrote:
> > Set default QP range to (1, 51) instead of (2, 32).
> >
> > QP = 0 is not well supported currently in libopenh264. If iMaxQp/iMinQp
> > equals 0, the QP range would be changed unexpectedly inside libopenh264
> > with a warning:
> >
> > Warning:Change QP Range from(0,51) to (12,42)
> >
> > Signed-off-by: Linjie Fu <linjie.fu at intel.com>
> > ---
> > [1]
> <https://github.com/cisco/openh264/blob/master/codec/encoder/core/src/
> encoder_ext.cpp#L375>
> > [2] <https://github.com/cisco/openh264/issues/3259>
> >
> >  libavcodec/libopenh264enc.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> >
> > diff --git a/libavcodec/libopenh264enc.c b/libavcodec/libopenh264enc.c
> > index ae6d17c..7cd1efe 100644
> > --- a/libavcodec/libopenh264enc.c
> > +++ b/libavcodec/libopenh264enc.c
> > @@ -135,6 +135,9 @@ FF_ENABLE_DEPRECATION_WARNINGS
> >      param.iTargetBitrate             = avctx->bit_rate;
> >      param.iMaxBitrate                = FFMAX(avctx->rc_max_rate, avctx-
> >bit_rate);
> >      param.iRCMode                    = RC_QUALITY_MODE;
> > +    // QP = 0 is not well supported, so default to (1, 51)
> > +    param.iMaxQp                     = avctx->qmax >= 0 ? av_clip(avctx->qmax, 1,
> 51) : 51;
> > +    param.iMinQp                     = avctx->qmin >= 0 ? av_clip(avctx->qmin, 1,
> avctx->qmax) : 1;
> 
> Should be param.iMaxQp. avctx->qmax may be <= 0.
> 
Fixed locally, thanks for pointing this out and the elaborations in IRC.

- Linjie