[FFmpeg-devel] 回复： [PATCH] avcodec/videotoolboxenc: add low-latency encoding

[Zhao Zhili]

> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of Rick Kern
> Sent: 2023年5月19日 21:37
> To: FFmpeg development discussions and patches <ffmpeg-devel at ffmpeg.org>
> Cc: zhilizhao(赵志立) <quinkblack at foxmail.com>
> Subject: Re: [FFmpeg-devel] 回复： [PATCH] avcodec/videotoolboxenc: add low-latency encoding
> 
> On Fri, May 19, 2023 at 1:56 AM 徐福隆 <839789740 at qq.com> wrote:
> 
> > Thank you for your review, and point out the details.
> > Actually, I have also considered this issue.
> > I see that some keys are used directly, some are used by compatibility.
> >
> 
> The compat_keys are used for symbols that might not exist. For constants
> available in the earliest version of VideoToolbox, compat_keys doesn't need
> to be used.

I curious to know what's the minimum supported version of macOS which
doesn't need dynamic loading symbols. I can't find such information. The question
applies to other OS too. It's not clear from configure, and I can't find the relevant
documentation.

> 
> Your patch looks good - I'll push it shortly.
> 
> 
> > I will use compat_key instead, and submit a new patch.
> >
> >
> > ------------------ 原始邮件 ------------------
> > 发件人:
> >                                                   ""zhilizhao(赵志立)""
> >
> > <quinkblack at foxmail.com>;
> > 发送时间: 2023年5月19日(星期五) 中午11:34
> > 收件人: "FFmpeg development discussions and patches"<
> > ffmpeg-devel at ffmpeg.org>;
> > 抄送: "徐福隆"<839789740 at qq.com>;
> > 主题: Re: [FFmpeg-devel] [PATCH] avcodec/videotoolboxenc: add
> > low-latency encoding
> >
> >
> >
> >
> >
> > > On May 19, 2023, at 11:17, xufuji456 <839789740 at qq.com> wrote:
> > >
> > > When using low-latency mode, it eliminates frame reordering
> > > and follows a one-in-one-out encoding mode
> > >
> > > Signed-off-by: xufuji456 <839789740 at qq.com>
> > > ---
> > > libavcodec/videotoolboxenc.c | 11 +++++++++++
> > > 1 file changed, 11 insertions(+)
> > >
> > > diff --git a/libavcodec/videotoolboxenc.c
> > b/libavcodec/videotoolboxenc.c
> > > index c6f22723d6..ae1ef32b2d 100644
> > > --- a/libavcodec/videotoolboxenc.c
> > > +++ b/libavcodec/videotoolboxenc.c
> > > @@ -1441,6 +1441,17 @@ static int
> > vtenc_create_encoder(AVCodecContext   *avctx,
> > >         }
> > >     }
> > >
> > > +    // low-latency mode: eliminate frame reordering,
> > follow a one-in-one-out encoding mode
> > > +    if ((avctx->flags &
> > AV_CODEC_FLAG_LOW_DELAY) && avctx->codec_id == AV_CODEC_ID_H264)
> > {
> > > +        status =
> > VTSessionSetProperty(vtctx->session,
> > >
> >
> +                  &nbsp
> ;                  
> > kVTVideoEncoderSpecification_EnableLowLatencyRateControl,
> > >
> >
> +                  &nbsp
> ;                  
> > kCFBooleanTrue);
> >
> > Please use compat_keys in case of
> > kVTVideoEncoderSpecification_EnableLowLatencyRateControl
> > isn’t available.
> >
> > > +
> > > +        if (status) {
> > > +           
> > av_log(avctx, AV_LOG_ERROR, "Error setting low latency property: %d\n",
> > status);
> > > +        }
> > > +    }
> > > +
> > >     status =
> > VTCompressionSessionPrepareToEncodeFrames(vtctx->session);
> > >     if (status) {
> > >         av_log(avctx,
> > AV_LOG_ERROR, "Error: cannot prepare encoder: %d\n", status);
> > > --
> > > 2.32.0 (Apple Git-132)
> > >
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