Pipe FFMPEG's output to S3 PutObject - go

Question

I'm trying to replicate the AWS Lambda solution of the following tutorial with Go AWS SDK. My process is a little bit more complicated though because I want to be able to do the following:
Convert the video to h265
Transpose it to m3u8 (HLS)
Upload the h265 video directly from pipe (without local copy)
Upload the m3u8 and ts files (apparently impossible to do without local copy, not sure though)
I came up with the following:
func upload(video_name string) {
var compress_args = []string{
"-loglevel", "fatal",
"-i", video_name + ".mp4",
"-vcodec", "libx265",
"-x265-params", "log-level=fatal",
"-crf", "28",
"-f", "mp4",
"-movflags", "frag_keyframe+empty_moov",
"-", // pipes output to stdout
}
var transpose_args = []string{
"-loglevel", "fatal",
"-i", "-", // Read input from stdin
"-vcodec", "libx265",
"-x265-params", "log-level=fatal",
"-crf", "28",
"-start_number", "0",
"-hls_time", "1",
"-hls_list_size", "0",
"-f", "hls", "tmp/" + video_name + ".m3u8",
}
cmd := exec.Command("ffmpeg", compress_args...)
cmd2 := exec.Command("tee", "new_" + video_name + ".mp4") // how to improve that ?
cmd3 := exec.Command("ffmpeg", transpose_args...)
cmd.Stderr = os.Stderr
cmd2.Stderr = os.Stderr
cmd3.Stderr = os.Stderr
cmd2.Stdin, _ = cmd.StdoutPipe()
cmd3.Stdin, _ = cmd2.StdoutPipe()
cmd3.Stdout = os.Stdout
cmd.Start()
cmd2.Start()
cmd3.Start()
cmd.Wait()
cmd2.Wait()
cmd3.Wait()
}
For now, what this does is that it pipes the compression, the tee and the transpose commands. The tee creates a local copy of the .mp4 and relay to the compression command. Now, I would like to be able to pass tee's output to the Body parameter for s3.PutObjectInput.
Should I use a Named Pipe, let tee write on it and then somehow pass that to the PutObjectInput? is it even possible? what are the other possibilities ?
Edit
I made the compressed file upload work by using named pipes and not waiting for the commands to finish (original idea). Here is the new code:
func upload(video_name string) {
// ARGS
syscall.Mkfifo("pipe", 0644)
// CMDS and STDOUT/STDIN redirections
named_pipe, _ := os.OpenFile("pipe", os.O_RDONLY|syscall.O_NONBLOCK, 0600)
defer named_pipe.Close()
syscall.SetNonblock(int(named_pipe.Fd()), false)
sess := session.Must(session.NewSession(&aws.Config{
Region: aws.String(region),
}))
uploader := s3manager.NewUploader(sess, func(u *s3manager.Uploader) {
u.PartSize = 5 * 1024 * 1024 // 5MB
})
compress_cmd.Start()
tee_cmd.Start()
transpose_cmd.Start()
_, err := uploader.UploadWithContext(context.Background(), &s3manager.UploadInput{
Bucket: aws.String(bucket),
Key: aws.String(video_name + ".mp4"),
Body: &reader{named_pipe},
})
}
where reader is:
type reader struct {
r io.Reader
}
func (r *reader) Read(p []byte) (int, error) {
return r.r.Read(p)
}
However, is there a way to wait for the whole process to finish before uploading the HLS output?
I tried waiting for transpose_cmd to finish after the UploadWithContext but this makes the Uploader quit prematurely.