ffmpeg with multiple outputs

[amazing-discoveries]

Hi,
is it possible to transcode with one ffmpeg node to two targets. In ffmpeg it would looks like:

ffmpeg -i input.ext -s 1024x576 -c:v libx264 [...] -f flv rtmp://stream1 -s 512x288 -c:v libx264 -f flv rtmp://stream2

I need this, because at the moment we stream with two ffmpeg nodes two resolutions, but they are not sync, and we need them sync for adaptive streaming.

[amazing-discoveries]

I found a way with tee:

    engine ff {
            enabled on;
            vfilter {
                filter_complex   '[0:v]split=2[s0][s1];[s0]null[v0];[s1]scale=512:-2[v1]';
                map         '[v0]';
                map         '[v1]';
                map         0:a;
            }
            vcodec          libx264;
            vfps            25;
            vthreads        2;
            vprofile        main;
            vpreset         slower;

            vparams {
                crf         23;
                g           25;
                maxrate     1200k;
                bufsize     1200k;
                refs        3;
                flags       +global_header;
            }

            acodec copy;

            aparams {
            }

            oformat         tee;
            output          "[select=\'v:0,a\':f=flv]rtmp://127.0.0.1:[port]/[app]/[stream]_full|[select=\'v:1,a\':f=flv]rtmp://127.0.0.1:[port]/[app]/[stream]_half";
        }

The delay is way better, but the problem is, that I have to encode both streams and I can't control the bitrate more exact for every stream.

[Alehap]

Hello,
Can you resolve this problem and could you share me the tips? @amazing-discoveries

[jb-alvarado]

Hi @Alehap,
because the configuration file is read from top to bottom, you can also use the commands accordingly. E.g. like this:

    engine ff {
        enabled on;
        vcodec          libx264;
        vprofile        main;
        vpreset         slower;

        vparams {
            crf         23;
            g           25;
            maxrate     1200k;
            bufsize     2400k;
            refs        3;
            flags       +global_header;
            c:a         copy;
            f           flv;
            y           rtmp://127.0.0.1:[port]/[app]/[stream]_full;
            s           512x288;
            c:v         libx264;
            preset      slower;
            profile:v   main;
            crf         23;
            g           25;
            maxrate     600k;
            bufsize     1200k;
            refs        3;
            flags       +global_header;
        }

        acodec copy;

        oformat         flv;
        output          rtmp://127.0.0.1:[port]/[app]/[stream]_half;
    }

[winlinvip]

For complex transcoding, you can use HTTP-Callback to hook the events, and do some tricks in your system.