Add ffmpeg command building

transcoder/src/stream.go

@@ -1,9 +1,108 @@
 package src
 
+import (
+	"context"
+	"fmt"
+	"log"
+	"os/exec"
+	"strings"
+	"sync"
+)
+
+func Min(a int32, b int32) int32 {
+	if a < b {
+		return a
+	}
+	return b
+}
+
+type Stream interface {
+	getTranscodeArgs(segments string) []string
+	getOutPath() string
+}
+
 type TranscodeStream struct {
-	File    FileStream
+	Stream
+	file    *FileStream
 	Clients []string
 	// true if the segment at given index is completed/transcoded, false otherwise
 	segments []bool
+	// the lock used for the segments array
+	lock sync.RWMutex
+	ctx  context.Context
 	// TODO: add ffmpeg process
 }
+
+func NewStream(file *FileStream) (*TranscodeStream, error) {
+	ret := TranscodeStream{
+		file:     file,
+		Clients:  make([]string, 4),
+		segments: make([]bool, len(file.Keyframes)),
+	}
+	// Start the transcode up to the 100th segment (or less)
+	ret.run(0, Min(100, int32(len(file.Keyframes))))
+	return &ret, nil
+}
+
+func (ts *TranscodeStream) run(start int32, end int32) error {
+	log.Printf(
+		"Starting transcode for %s (from %d to %d out of %d segments)",
+		ts.file.Path,
+		start,
+		end,
+		len(ts.file.Keyframes),
+	)
+
+	// We do not need the first value (start of the transcode)
+	segments := make([]string, end-start-1)
+	for i := range segments {
+		segments[i] = fmt.Sprintf("%.6f", ts.file.Keyframes[int(start)+i+1])
+	}
+	segments_str := strings.Join(segments, ",")
+
+	args := []string{
+		"-nostats", "-hide_banner", "-loglevel", "warning",
+		"-copyts",
+
+		"-ss", fmt.Sprintf("%.6f", ts.file.Keyframes[start]),
+		"-to", fmt.Sprintf("%.6f", ts.file.Keyframes[end]),
+		"-i", ts.file.Path,
+	}
+	args = append(args, ts.getTranscodeArgs(segments_str)...)
+	args = append(args, []string{
+		"-f", "segment",
+		"-segment_time_delta", "0.2",
+		"-segment_format", "mpegts",
+		"-segment_times", segments_str,
+		"-segment_start_number", fmt.Sprint(start),
+		"-segment_list_type", "flat",
+		"-segment_list", "pipe:1",
+		ts.getOutPath(),
+	}...)
+
+	cmd := exec.CommandContext(
+		ts.ctx,
+		"ffmpeg",
+		args...,
+	)
+	log.Printf("Running %s", strings.Join(cmd.Args, " "))
+
+	return nil
+}
+
+func (ts *TranscodeStream) GetIndex(client string) (string, error) {
+	index := `#EXTM3U
+#EXT-X-VERSION:3
+#EXT-X-PLAYLIST-TYPE:VOD
+#EXT-X-ALLOW-CACHE:YES
+#EXT-X-TARGETDURATION:4
+#EXT-X-MEDIA-SEQUENCE:0
+`
+
+	for segment := 1; segment < len(ts.file.Keyframes); segment++ {
+		index += fmt.Sprintf("#EXTINF:%.6f\n", ts.file.Keyframes[segment]-ts.file.Keyframes[segment-1])
+		index += fmt.Sprintf("segment-%d.ts\n", segment)
+	}
+	index += `#EXT-X-ENDLIST`
+	return index, nil
+}

transcoder/src/videostream.go

@@ -0,0 +1,33 @@
+package src
+
+import "fmt"
+
+type VideoStream struct {
+	TranscodeStream
+	quality Quality
+}
+
+func (vs *VideoStream) getOutPath() string {
+	return fmt.Sprintf("%s/segment-%s-%%03d.ts", vs.file.Out, vs.quality)
+}
+
+func (vs *VideoStream) getTranscodeArgs(segments string) []string {
+	if vs.quality == Original {
+		return []string{"-map", "0:V:0", "-c:v", "copy"}
+	}
+
+	return []string{
+		// superfast or ultrafast would produce a file extremly big so we prever veryfast or faster.
+		"-map", "0:V:0", "-c:v", "libx264", "-crf", "21", "-preset", "faster",
+		// resize but keep aspect ratio (also force a width that is a multiple of two else some apps behave badly.
+		"-vf", fmt.Sprintf("scale=-2:'min(%d,ih)'", vs.quality.Height()),
+		// Even less sure but bufsize are 5x the avergae bitrate since the average bitrate is only
+		// useful for hls segments.
+		"-bufsize", fmt.Sprint(vs.quality.MaxBitrate() * 5),
+		"-b:v", fmt.Sprint(vs.quality.AverageBitrate()),
+		"-maxrate", fmt.Sprint(vs.quality.MaxBitrate()),
+		// Force segments to be split exactly on keyframes (only works when transcoding)
+		"-force_key_frames", segments,
+		"-strict", "-2",
+	}
+}