[FFmpeg-devel] [PATCH v4 2/9] lavc/libopenh264enc: add default gop size and bit rate

[Fu, Linjie]

> From: Martin Storsjö <martin at martin.st>
> Sent: Tuesday, April 28, 2020 03:28
> > static const AVCodecDefault svc_enc_defaults[] = {
> > +    { "b",         "0"     },
> > +    { "g",         "120"   },
> >     { "qmin",      "-1"    },
> 
> Why do you hardcode a value for g here, but put the default bitrate value
> in the code above? Wouldn't it be clearer to have both defaults here at
> the same place?
> 
A default value in svc_enc_defaults[] would help to distinguish between
"the user specified the bitrate to be <x>" vs. "the user did not specify anything
about the target bitrate", as Anton has suggested in [1].

Considering about your suggestions in patch 1/9, IMO it seems to be more reasonable
to keep the uiIntraPeriod untouched. The libopenh264 library would fill the default
value of uiIntraPeriod to 0, and as a consequence the gop size would be rather large.

Updated the default "g" to "-1", same as libx264 did.
(Note that it's not acceptable for bitrate, since bitrate = 0 as default in library is not
valid)

- Linjie

[1] https://lists.ffmpeg.org/pipermail/ffmpeg-devel/2020-April/260320.html