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

[Rick Kern <kernrj@gmail.com>]

On Fri, May 19, 2023 at 2:06 PM Zhao Zhili <quinkblack@foxmail.com> wrote:

>
> > From: ffmpeg-devel <ffmpeg-devel-bounces@ffmpeg.org> On Behalf Of Rick
> Kern
> > Sent: 2023年5月19日 21:37
> > To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
> > Cc: zhilizhao(赵志立) <quinkblack@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@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.
>
VideoToolbox was released in MacOS 10.8 and iOS 8.0. I'll update the
compat_keys docs with this info.


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