Transcoder Configuration - Storm Streaming Server

Transcoder is a powerful tool for rescaling video materials. Storm uses open-source FFMPEG for all tasks related to transcoding. If FFMPEG is not installed on your system, transcoding will not be possible. In order to check if FFMPEG is present, please try this command line:

                        
ffmpeg -version
                    

If you are unsure where FFMPEG binaries are located, please you the following command:

Sample Configuration

Below you’ll find a sample configuration for preferences.xml file.

                        
<Transcoder>
	<FFMPEG>
        <Path>/usr/bin/ffmpeg</Path>
		<Command>-re -nostdin -i {SOURCE_INPUT} -vsync 1 -vcodec libx264 -preset:v {CPU_USAGE_PRESET} -vf scale={OUTPUT_WIDTH}:{OUTPUT_HEIGHT} -tune {TUNE} -g 30 -fflags nobuffer -probesize 32 -analyzeduration 0 -b:v {VIDEO_BITRATE} -acodec aac -b:a {AUDIO_BITRATE} -async 1 -f flv {STREAM_OUTPUT}</Command>
	</FFMPEG>
    <TranscodeTaskLimit>5</TranscodeTaskLimit>>
    <PresetList>
        <Preset name="360p" suffix="_360p">
            <Resolution height="360" />
            <Bitrate video="1000" audio="50" />
            <KeyFrameInterval>1</KeyFrameInterval>
            <CPUUsagePreset>ultrafast</CPUUsagePreset>
            <Profile>main</Profile>
            <Tune>zerolatency</Tune>
        </Preset>
        <Preset name="480p" suffix="_480p">
            <Resolution height="480" />
            <Bitrate video="1500" audio="50" />
            <KeyFrameInterval>1</KeyFrameInterval>
            <CPUUsagePreset>ultrafast</CPUUsagePreset>
            <Profile>main</Profile>
            <Tune>zerolatency</Tune>
        </Preset>
        <Preset name="720p" suffix="_720p">
            <Resolution height="720" />
            <Bitrate video="3000" audio="100" />
            <KeyFrameInterval>1</KeyFrameInterval>
            <CPUUsagePreset>ultrafast</CPUUsagePreset>
            <Profile>main</Profile>
            <Tune>zerolatency</Tune>
        </Preset>
    </PresetList>
</Transcoder>
                    

FFMPEG Path

Path should point to FFMPEG binary location on your system. You can use which to find the right location.

                        
which ffmpeg
                    

Note: Storm will look for FFMPEG in standard system paths if this tag is left empty.

FFMPEG Command

Storm performs transcoding by controlling individual FFMPEG processes. You may want to tune your FFMPEG configuration by changing default encoder (for example to NVENC) or adding some preferences. This command line is being used to execute commands and can be modified.

                        
-re -nostdin -i {SOURCE_INPUT} -vsync 1 -vcodec libx264 -preset:v {CPU_USAGE_PRESET} -vf scale={OUTPUT_WIDTH}:{OUTPUT_HEIGHT} -tune {TUNE} -g 30 -fflags nobuffer -probesize 32 -analyzeduration 0 -b:v {VIDEO_BITRATE} -acodec aac -b:a {AUDIO_BITRATE} -async 1 -f flv {STREAM_OUTPUT}
                    

Below you’ll find list of available variables:

TranscodeTaskLimit

Encoding video and audio is a highly demanding process that consumes significant amounts of system resources — including both CPU and memory. The TranscodeTaskLimit parameter sets an upper limit for the number of simultaneous transcoding processes. We recommend configuring this value to utilize no more than 70–80% of the server's available resources.

TranscodingPreset

Useful Links

1. FFMPEG Manual - https://ffmpeg.org/ffmpeg.html