[FFmpeg-devel] [PATCH v5 2/5] lavc/libopenh264enc: add default gop size and bit rate

[Fu, Linjie]

> From: Martin Storsjö <martin at martin.st>
> Sent: Tuesday, April 28, 2020 18:29
> To: FFmpeg development discussions and patches <ffmpeg-
> devel at ffmpeg.org>
> Cc: Fu, Linjie <linjie.fu at intel.com>
> Subject: Re: [FFmpeg-devel] [PATCH v5 2/5] lavc/libopenh264enc: add
> default gop size and bit rate
> 
> On Tue, 28 Apr 2020, Linjie Fu wrote:
> 
> > It would be 200kbps bitrate with gop size = 12 by default
> > which generated too many IDR frames in rather low bit rate.
> > The quality would be poor.
> >
> > Set these default values to -1 to check whether it's specified
> > by user explicitly.
> >
> > Use 2Mbps bitrate as nvenc sugguested, and leave gop size
> > untouched in libopenh264.
> >
> > Signed-off-by: Linjie Fu <linjie.fu at intel.com>
> > ---
> > libavcodec/libopenh264enc.c | 9 +++++++--
> > 1 file changed, 7 insertions(+), 2 deletions(-)
> >
> > diff --git a/libavcodec/libopenh264enc.c b/libavcodec/libopenh264enc.c
> > index 1b6b53a..0951412 100644
> > --- a/libavcodec/libopenh264enc.c
> > +++ b/libavcodec/libopenh264enc.c
> > @@ -37,6 +37,8 @@
> > #define SM_SIZELIMITED_SLICE SM_DYN_SLICE
> > #endif
> >
> > +#define TARGET_BITRATE_DEFAULT 2*1000*1000
> > +
> > typedef struct SVCContext {
> >     const AVClass *av_class;
> >     ISVCEncoder *encoder;
> > @@ -132,7 +134,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
> >     param.fMaxFrameRate              = 1/av_q2d(avctx->time_base);
> >     param.iPicWidth                  = avctx->width;
> >     param.iPicHeight                 = avctx->height;
> > -    param.iTargetBitrate             = avctx->bit_rate;
> > +    param.iTargetBitrate             = avctx->bit_rate > 0 ? avctx->bit_rate :
> TARGET_BITRATE_DEFAULT;
> >     param.iMaxBitrate                = FFMAX(avctx->rc_max_rate, avctx-
> >bit_rate);
> >     param.iRCMode                    = RC_QUALITY_MODE;
> >     // QP = 0 is not well supported, so clip to (1, 51)
> > @@ -148,7 +150,8 @@ FF_ENABLE_DEPRECATION_WARNINGS
> >     param.bEnableFrameSkip           = s->skip_frames;
> >     param.bEnableLongTermReference   = 0;
> >     param.iLtrMarkPeriod             = 30;
> > -    param.uiIntraPeriod              = avctx->gop_size;
> > +    if (avctx->gop_size)
> > +        param.uiIntraPeriod          = avctx->gop_size;
> 
> This should be gop_size > 0, or maybe >= 0. Otherwise we'll end up setting
> the default -1.
> 
Ops, fixed and thanks for pointing this out.