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[FFmpeg-devel] flvenc: flush after write header

Message ID tencent_AA558BE20D385F2FB591B8E21A3F06E80006@qq.com
State New
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Series [FFmpeg-devel] flvenc: flush after write header
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Commit Message

Lingjiang Fang Oct. 28, 2021, 6:32 a.m. UTC
keep align with movenc, or it seems a little weired when debug
---
 libavformat/flvenc.c | 2 ++
 1 file changed, 2 insertions(+)

Comments

Steven Liu Oct. 28, 2021, 12:50 p.m. UTC | #1
> 2021年10月28日 下午2:32,Lingjiang Fang <vacingfang@foxmail.com> 写道:
> 
> keep align with movenc, or it seems a little weired when debug
> ---
> libavformat/flvenc.c | 2 ++
> 1 file changed, 2 insertions(+)
> 
> diff --git a/libavformat/flvenc.c b/libavformat/flvenc.c
> index 3f24c7e192..f4798dc9a6 100644
> --- a/libavformat/flvenc.c
> +++ b/libavformat/flvenc.c
> @@ -767,6 +767,8 @@ static int flv_write_header(AVFormatContext *s)
>         flv_write_codec_header(s, s->streams[i]->codecpar, 0);
>     }
> 
> +    avio_flush(pb);
> +
>     flv->datastart_offset = avio_tell(pb);
>     return 0;
> }
> -- 
> 2.29.2
> 
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> 
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
> 

LGTM

Thanks

Steven Liu
Lingjiang Fang Nov. 2, 2021, 3:54 a.m. UTC | #2
On Thu, 28 Oct 2021 20:50:05 +0800
Steven Liu <lq@chinaffmpeg.org> wrote:

ping for review or apply :)

> 
> 
> > 2021年10月28日 下午2:32,Lingjiang Fang <vacingfang@foxmail.com>
> > 写道:
> > 
> > keep align with movenc, or it seems a little weired when debug
> > ---
> > libavformat/flvenc.c | 2 ++
> > 1 file changed, 2 insertions(+)
> > 
> > diff --git a/libavformat/flvenc.c b/libavformat/flvenc.c
> > index 3f24c7e192..f4798dc9a6 100644
> > --- a/libavformat/flvenc.c
> > +++ b/libavformat/flvenc.c
> > @@ -767,6 +767,8 @@ static int flv_write_header(AVFormatContext *s)
> >         flv_write_codec_header(s, s->streams[i]->codecpar, 0);
> >     }
> > 
> > +    avio_flush(pb);
> > +
> >     flv->datastart_offset = avio_tell(pb);
> >     return 0;
> > }
> > -- 
> > 2.29.2
> > 
> > _______________________________________________
> > ffmpeg-devel mailing list
> > ffmpeg-devel@ffmpeg.org
> > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> > 
> > To unsubscribe, visit link above, or email
> > ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
> > 
> 
> LGTM
> 
> Thanks
> 
> Steven Liu
> 
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> 
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".



Regards,
Lingjiang Fang
Martin Storsjö Nov. 2, 2021, 7:14 a.m. UTC | #3
On Thu, 28 Oct 2021, Steven Liu wrote:

>
>
>> 2021年10月28日 下午2:32,Lingjiang Fang <vacingfang@foxmail.com> 写道:
>> 
>> keep align with movenc, or it seems a little weired when debug
>> ---
>> libavformat/flvenc.c | 2 ++
>> 1 file changed, 2 insertions(+)
>> 
>> diff --git a/libavformat/flvenc.c b/libavformat/flvenc.c
>> index 3f24c7e192..f4798dc9a6 100644
>> --- a/libavformat/flvenc.c
>> +++ b/libavformat/flvenc.c
>> @@ -767,6 +767,8 @@ static int flv_write_header(AVFormatContext *s)
>>         flv_write_codec_header(s, s->streams[i]->codecpar, 0);
>>     }
>> 
>> +    avio_flush(pb);
>> +
>>     flv->datastart_offset = avio_tell(pb);
>>     return 0;
>> }
>> -- 
>> 2.29.2
>> 
>
> LGTM

No, please don't apply this.

We intentionally move in the other direction; every explicit avio_flush() 
is a potential performance bottleneck, and we've been working on reducing 
the number of extra avio_flush() calls.

When streaming, where latency is relevant, the libavformat generic code 
already flushes automatically after the header and after each packet. When 
latency is not relevant, we explicitly want to avoid extra avio_flush() 
because each of them cause extra writes (that otherwise could be 
buffered). You can also set the option "-flush_packets 1" (or "-fflags 
flush_packets") to make the generic code flush when relevant. See e.g. the 
flush_if_needed() function in libavformat/mux.c.

// Martin
diff mbox series

Patch

diff --git a/libavformat/flvenc.c b/libavformat/flvenc.c
index 3f24c7e192..f4798dc9a6 100644
--- a/libavformat/flvenc.c
+++ b/libavformat/flvenc.c
@@ -767,6 +767,8 @@  static int flv_write_header(AVFormatContext *s)
         flv_write_codec_header(s, s->streams[i]->codecpar, 0);
     }
 
+    avio_flush(pb);
+
     flv->datastart_offset = avio_tell(pb);
     return 0;
 }