[FFmpeg-user] Buffer Size for Stream Copy

[Wu-bin Zhen]

On Tue, Aug 20, 2013 at 7:31 PM, Paul B Mahol <onemda at gmail.com> wrote:

> On 8/20/13, Wu-bin Zhen <vvubin at gmail.com> wrote:
> > On Fri, Aug 16, 2013 at 3:31 PM, Wu-bin Zhen <vvubin at gmail.com> wrote:
> >
> >> Hello ffmpeg,
> >>
> >> I am using ffmpeg to grab h264 video stream and aac audio stream from an
> >> internet based hardware encoder with the codec copy option, and it works
> >> pretty well. Now, I start to wonder if I can use the '-bufsize' option
> >> for
> >> the stream copy, just in case when the network is temporally slow down,
> >> or
> >> the encoder is suddenly chocking for some reason. I googled a little bit
> >> about the 'bufsize' option, and found that most people use the option
> for
> >> encoding.
> >>
> >> So my question is: Do you think using 'bufsize' option will be helpful
> >> for
> >> the stream copy? If so, what would be the recommended buffer size? My
> >> internet encoder produces video stream with 4000kbits/sec, and audio
> >> stream
> >> with 128kbits/sec.
> >>
> >> Thanks, and have a great weekend.
> >> -w
> >>
> >
> > Sorry if I didn't explain clearly. So ffmpeg works fine when I specify
> the
> > option '-bufsize', but later I realized that it actually doesn't care the
> > value of the bufsize option. The ffmpeg command below works fine without
> > complaining anything about the bufsize value:
> >
> >> ffmpeg -i http://192.168.1.224:1881/stream.ts -bufsize helloworld
> -vcodec
> > copy -acodec copy buffer_test.ts
> >
> > So I start to wonder if ffmpeg doesn't do anything about '-bufsize' for
> the
> > stream copy.
> > Please advise. Thanks
>
> As explainded in documentation and by ffmpeg itself, 'bufsize' is used
> for audio/video encoding only.
>
> -bufsize           <int>        E..VA. set ratecontrol buffer size (in
> bits) (from INT_MIN to INT_MAX) (default 0
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Thanks for your clear explanation, so I can forget about this option for
copy streams. By the way, do you think is there a way to set buffer for the
stream copy? For my case the copy is based on the network, not from the
local hardware, so I am worry when the network or the encoder is temporally
inaccessible.

I will appreciate if you would advise any method to make the stream copy
more stable.
-w