golang ffmpeg imagepipe streaming

README.md

using golang to create image pipe for ffmpeg

If you want to stream a slideshow using ffmpeg, it seems like one easy way to do it is to create an imagepipe of the files.

This can then be streamed to twitch.tv or youtube ... https://trac.ffmpeg.org/wiki/StreamingGuide

This sample cycles between images on disk

usage

go run main.go -duration 1.5 -fps 25 *.png | ./stream.sh twitch_streaming_key_goes_here

thoughts

• if the FPS is too low, it won't actually send enough data to cause images to be read often enough (it seems)
• ffmpeg will rescale the images to the resolution specified in stream.sh
• ffmpeg seems want the imagepipe (all the images) to be the same format (although it will scale each independantly)

main.go

package main

import (
	"bufio"
	"flag"
	"os"
	"time"
)

func main() {
	fps := flag.Float64("fps", 10, "frames to send per second")
	duration := flag.Float64("duration", 2, "seconds to display an image")
	flag.Parse()

	frames := int(*fps * *duration)
	delay := time.Second / time.Duration(*fps)

	out := bufio.NewWriterSize(os.Stdout, 4096)

	for {
		for _, f := range flag.Args() {
			data, err := os.ReadFile(f)
			if err == nil {
				for i := 0; i < frames; i++ {
					out.Write(data)
					out.Flush()
					time.Sleep(delay)
				}
			}
		}
	}
}

stream.sh

#!/bin/bash

stream_key="$1" # key will be passed as an agument from the command line
stream_server="iad05.contribute.live-video.net" # see https://stream.twitch.tv/ingests for list

threads="2" # max 6
cbr="3000k" # constant bitrate (should be between 1000k–3000k)
quality="medium" # one of the many FFmpeg presets
loglevel="warning" # supress unecessary information from printing

ffmpeg \
    -f image2pipe -i -  \
    -loglevel "${loglevel}" \
    -f flv  \
    -vcodec libx264  -b:v ${cbr} \
    -minrate ${cbr} -maxrate ${cbr} -pix_fmt yuv420p \
    -preset "${quality}" -tune film \
    -strict normal \
    -bufsize ${cbr} \
    "rtmp://${stream_server}/app/${stream_key}"

https://stackoverflow.com/questions/46397240/ffmpeg-image2pipe-producing-broken-video is interesting

cat 2017*.png | ./ffmpeg -f image2pipe -framerate 1 -i - -c:v libx264 -vf format=yuv420p -r 25 -movflags +faststart out.mp4

• Use the -framerate input option instead of -r for image2pipe demuxer.
• Many players have trouble with such low frame rate MP4. Add the -r output option to give it a more normal output rate. ffmpeg will duplicate frames to match but it will still look as if it is 1 fps.
• Add -vf format=yuv420p (or the alias -pix_fmt yuv420p) to make the output use a widely compatible pixel format.
• Use -movflags +faststart to enable faster starting playback.