[Guide] Two PC configuration without Capturecard

• Intel Quicksync support

• RTMP server with NGINX under Ubuntu (ubuntu server virtual machine or standalone ubuntu server)
• Good CPU. I use Intel Core I7 3770K overclocked to 4500MHz. It allow to transcode 1080p with fast preset and 720p with medium preset. Free memory not important, because ubuntu use 200k maximum.

• Use CBR - enabled
• Use custom buffer size - enabled
• Max bitrate
  • 25000 for 1080p
    15000 for 720p
• Buffer size - 7000. Buffer size more then 7000 can cause periodical disconnections from nginx.

• Streaming Service - custom
• Server - rtmp://second_pc_ip_address/transcode

• Set resolution and FPS according to your needs

• Use Quick Sync - enabled

rtmp {
    server {
        listen 1935;   
            chunk_size 4000;   

        application transcode {
            live on;
            record off;           
            exec ffmpeg -re -i rtmp://localhost:1935/trans/$name -vcodec libx264 -preset medium -x264opts nal-hrd=cbr:force-cfr=1:keyint=60 -r 30 -b:v 2000k -maxrate 2000k -bufsize 2000k -threads 12 -s hd720 -sws_flags spline -acodec copy -f flv rtmp://localhost:1935/live/${name};                  
        }
        application live {
             live on;
             record off;
             push rtmp://live-lhr.twitch.tv/app/twitch_key;
        }
    }
}

• preset medium. Corresponding OBS option - x264 CPU Preset. Change according to your CPU.
• keyint=60. Corresponding OBS option - Keyframe Interval. Replace 60 by [OBS FPS setting]*2.
• nal-hrd=cbr. Corresponding OBS option - Enable CBR padding.
• force-cfr=1. Corresponding OBS option - Use CFR.
• r 30. Corresponding OBS option - FPS. Replace 30 by OBS FPS setting.
• b:v 2000k. Corresponding OBS option - Max Bitrate. Set according to your needs.
• maxrate 2000k. Corresponding OBS option - Max Bitrate. Set according to your needs.
• bufsize 2000k. Corresponding OBS option - Buffer size. Set to Max Bitrate or use custom buffer size according to your needs.
• threads 12. Set to 1.5 * logical processors, rounded down. In some cases ffmpeg/avconv can't detect CPU and use only one thread, so better to set it manually.
• s hd720. Resolution of target video. Also you can use following syntax: -s 1280x720. Video quality will be better in case you use downscaling by ffmpeg instead of first PS, because quicksync add too much sharpness into downscaled video. Remove this option in case you are streaming in 1080p.
• sws_flags spline. Downscale method. You can try "lanczos" method instead of "spline" as alternative. Remove this option in case you are streaming in 1080p.
• rtmp://live-lhr.twitch.tv/app/twitch_key. Replace by your favorite stream server and key. List of twitch.tv servers: http://bashtech.net/twitch/ingest.php

Jack0r said:

Oh and one thing to notice: nginx-rtmp-module on windows cannot use "exec" so you would have to run ffmpeg on your own in this case. But its not a big problem. On a Linux machine you can use the nginx configuration as in your example.

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Jack0r said:

And I didnt know about the buffer setting, this could explain some trouble I had recently, will investigate this!

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dodgepong said:

Nice guide. It's worth noting that the RTMP server needs to have a good CPU to do the transcoding. I know that in my guide, I make a point of saying that a simple RTMP server doesn't need to be very powerful, but in this case, it actually does.

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z0rz said:

Will the end quality be better if the first PC encodes regularly instead of using QSV?

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nrw2000 said:

If someone know how to use avconv and correspond to new Twitch requirements, please let me know.

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Jack0r said:

ehm Keyframe interval is normally:
g = FPS * desired Interval
g = 30 * 2 = 60 for 30fps streaming
g = 60 * 2 = 120 for 60 fps streaming

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