[FFmpeg-devel] [PATCH 03/10] lavc/libopenh264enc: add default gop size and bit rate

[Fu, Linjie]

> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of
> Anton Khirnov
> Sent: Friday, April 10, 2020 18:14
> To: FFmpeg development discussions and patches <ffmpeg-
> devel at ffmpeg.org>
> Subject: Re: [FFmpeg-devel] [PATCH 03/10] lavc/libopenh264enc: add
> default gop size and bit rate
> 
> Quoting Linjie Fu (2020-04-06 13:14:46)
> > Signed-off-by: Linjie Fu <linjie.fu at intel.com>
> > ---
> >  libavcodec/libopenh264enc.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/libavcodec/libopenh264enc.c b/libavcodec/libopenh264enc.c
> > index c7ae5b1..3ff5be7 100644
> > --- a/libavcodec/libopenh264enc.c
> > +++ b/libavcodec/libopenh264enc.c
> > @@ -335,6 +335,8 @@ static int svc_encode_frame(AVCodecContext
> *avctx, AVPacket *avpkt,
> >  }
> >
> >  static const AVCodecDefault svc_enc_defaults[] = {
> > +    { "b",         "2M"    },
> > +    { "g",         "120"   },
> 
> Why these values specifically? 

According to the default settings in nvenc (b = 2M) and vaapi encoder for h264 (g = 120).

>What happens if we leave them unset?

It would be 200kbps bitrate with gop size = 12.

There would be too much IDR frames with in small bitrate, which leads to
a poor quality. 

 (I should have added such statements in the commit message)

- Linjie