[FFmpeg-user] Ultra-low latency streaming

[Jimmy Asher]

From FFMPEG prospective, the less it has to do to the raw video the faster it can push it out - If the raw video is already at your target resolution that would help


As stated in your linked articles decreasing buffer sizes, using zero latency tuning and very fast presets as well as disabling the client caching is pretty much how I know to decrease latency

Eliminating as many items in your work flow as you can would also help lower your latency


If you can eliminate the use of FFServer that should help decrease the latency - I believe ffmpeg can output a rtp stream without ffserver’s assistance






On 2/8/16, 8:58 AM, "ffmpeg-user on behalf of Federico Salvioli" <ffmpeg-user-bounces at ffmpeg.org on behalf of raveningrocks at hotmail.com> wrote:

>Dear all,
>
>     First of all, I would like to thank you all the developers as even if I
>am no expert in FFmpeg I have been using it for numerous applications and
>your tool is really awesome! Thanks guys.
>
> 
>
>Some time ago I have been asked to setup a streaming server with the lowest
>amount of latency possible from a Firewire camera to another computer. The
>video feedback is used for teleoperation so the stream has soft real-time
>requirements. I have crawled the internet for a while and I saw various
>posts on this topic but sometimes maybe too old to be useful or sometimes a
>bit generic. I collected and reviewed the following:
>
> 
>
>http://fomori.org/blog/?p=1213-This guy has an interesting article, I will
>have a trial to reproduce some of his results.
>
>https://trac.ffmpeg.org/wiki/StreamingGuide
>
>http://ffmpeg.gusari.org/viewtopic.php?f=11
><http://ffmpeg.gusari.org/viewtopic.php?f=11&t=2002> &t=2002
>
>and some others.
>
> 
>
>I ended up setting up a system which looks like the following.
>
> 
>
>  ------------  firewire -----------------------  pipe  -----------  .ffm
>------------   rtsp    --------------------
>
>| Camera  |   ==>    |  frame grabber |   => | ffmpeg | => | ffserver |   =>
>| ffmpeg/ffplay |
>
>  ------------                 -----------------------
>------------         ------------               --------------------
>
> 
>
>I was unable to use the libdc1394 format to capture the feed from the camera
>so I used a previously written program to grab the frames and then pipe the
>raw yuv420p frames to ffmpeg.
>
>With this setup I managed to obtain around 3 seconds of latency. It is
>acceptable as the teleoperation happens not at a very low level but I would
>like to reach sub-second latencies. The priority should be given to latency
>and after to bandwidth as normally the streams travels on wifi LAN.
>
> 
>
>FFmpeg is launched with this command:
>
> 
>
>ffmpeg -hide_banner -f rawvideo -pixel_format gray -video_size 1280x960
>-framerate 5 -i - -an http://localhost:8080/stream.ffm
>
> 
>
>and FFserver:
>
> 
>
><Feed stream.ffm>
>
>      File /tmp/stream.ffm
>
>      FileMaxSize 200K
>
>      ACL allow 192.168.0.0 192.168.255.255
>
></Feed>
>
> 
>
><Stream XB3-240.h264>
>
>      Feed stream.ffm
>
>      Format rtp
>
>      
>
>      VideoCodec libx264
>
>      PixelFormat yuv420p
>
>      VideoFrameRate 4
>
>      VideoSize 320x240
>
>      
>
>      AVOptionVideo crf 23
>
>      AVOptionVideo profile baseline
>
> 
>
>      #VideoIntraOnly
>
>      VideoGopSize 8
>
>      
>
>      NoAudio
>
>      AVOptionAudio flags +global_header
>
></Stream>
>
> 
>
>
> 
>
>A few questions:
>
>-          I was unable to find out how to measure latency in every stage of
>the stream, is there a clever method to do it different from quick and dirty
>solutions as shown in the first link <http://fomori.org/blog/?p=1213> ? 
>
>-          May you be able to suggest how to reduce latency as much as
>possible at OS and ffmpeg/ffserver and network level.
>
>-          I would like to stick to H264 but other option may be evaluated
>in case they may bring much better results.
>
> 
>
>Thanks in advance for any help,
>
> 
>
>Best regards,
>
>Federico Salvioli.
>
> 
>
> 
>
> 
>
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