Add "cache/encode" controller

server/ctrlsubsonic/handlers_cache.go

@@ -0,0 +1,155 @@
+package ctrlsubsonic
+
+import (
+	"net/http"
+	"path"
+	"fmt"
+
+	"io"
+	"os"
+	"os/exec"
+
+	"github.com/cespare/xxhash"
+)
+
+type encoderProfile struct {
+	format string
+	bitrate string
+	ffmpegOptions []string
+	forceRG bool
+}
+
+var (
+	ENC_PROFILES = map[string]*encoderProfile {
+		"mp3"    : {  "mp3", "128k", []string{"-c:a", "libmp3lame"}                    , false },
+		"mp3_rg" : {  "mp3", "128k", []string{"-c:a", "libmp3lame"}                    , true  },
+		"opus"   : { "opus",  "96k", []string{"-c:a", "libopus", "-vbr", "constrained"}, false },
+		"opus_rg": { "opus",  "96k", []string{"-c:a", "libopus", "-vbr", "constrained"}, true  },
+	}
+	BUF_LEN = 4096
+)
+
+func StreamTrack(w http.ResponseWriter, r *http.Request, trackPath string, client string, cachePath string) {
+	// Guess required format based on client:
+	profile_name := detectFormat(client)
+	profile := ENC_PROFILES[profile_name]
+
+	cacheFile := path.Join(cachePath, getCacheKey(trackPath, profile_name))
+
+	if fileExists(cacheFile) {
+		fmt.Printf("`%s`: cache [%s/%s] hit!\n", trackPath, profile.format, profile.bitrate)
+		http.ServeFile(w, r, cacheFile)
+	} else {
+		fmt.Printf("`%s`: cache [%s/%s] miss!\n", trackPath, profile.format, profile.bitrate)
+		EncodeTrack(w, r, trackPath, cacheFile, profile)
+	}
+}
+
+func EncodeTrack(w http.ResponseWriter, r *http.Request, trackPath string, cachePath string, profile *encoderProfile) {
+	// Prepare the command and file descriptors:
+	cmd := ffmpegCommand(trackPath, profile)
+	pipeReader, pipeWriter := io.Pipe()
+	cmd.Stdout = pipeWriter
+	cmd.Stderr = pipeWriter
+
+	// Create cache file:
+	cacheFile, err := os.Create(cachePath)
+	if err != nil {
+		fmt.Printf("Failed to write to cache file `%s`: %s\n", cachePath, err)
+	}
+
+	//// I'm still unsure if buffer version (writeCmdOutput) is any better than io.Copy-based one (copyCmdOutput).
+	//// My initial goal here is to start streaming response ASAP, with smallest TTFB. More testing needed. -- @spijet
+	// Start up writers for cache file and HTTP response:
+	// go copyCmdOutput(w, cacheFile, pipeReader)
+	go writeCmdOutput(w, cacheFile, pipeReader)
+
+	// Run FFmpeg:
+	cmd.Run()
+
+	// Close all pipes and flush cache file:
+	pipeWriter.Close()
+	cacheFile.Sync()
+	cacheFile.Close()
+
+	fmt.Printf("`%s`: Encoded track to [%s/%s] successfully\n", trackPath, profile.format, profile.bitrate)
+}
+
+// Copy command output to HTTP response body using io.Copy (simpler, but may increase TTFB)
+func copyCmdOutput(res http.ResponseWriter, cache *os.File, pipeReader *io.PipeReader) {
+	// Set up a MultiWriter to feed the command output
+	// to both cache file and HTTP response:
+	w := io.MultiWriter(res, cache)
+
+	// Start copying!
+	if _, err := io.Copy(w, pipeReader); err != nil {
+		fmt.Printf("Error while writing encoded output: %s\n", err)
+	}
+}
+
+// Copy command output to HTTP response manually with a buffer (should reduce TTFB)
+func writeCmdOutput(res http.ResponseWriter, cache *os.File, pipeReader *io.PipeReader) {
+	buffer := make([]byte, BUF_LEN)
+	for {
+		n, err := pipeReader.Read(buffer)
+		if err != nil {
+			pipeReader.Close()
+			break
+		}
+
+		data := buffer[0:n]
+		res.Write(data)
+		cache.Write(data)
+		if f, ok := res.(http.Flusher); ok {
+			f.Flush()
+		}
+		//reset buffer
+		for i := 0; i < n; i++ {
+			buffer[i] = 0
+		}
+	}
+}
+
+func fileExists(filename string) bool {
+	info, err := os.Stat(filename)
+	if os.IsNotExist(err) {
+		return false
+	}
+	return !info.IsDir()
+}
+
+// Pre-format the FFmpeg command with needed options:
+func ffmpegCommand(filePath string, profile *encoderProfile) *exec.Cmd {
+	ffmpegArgs := []string{
+		"-v", "0", "-i", filePath, "-map", "0:0",
+		"-vn", "-b:a", profile.bitrate,
+	}
+	ffmpegArgs = append(ffmpegArgs, profile.ffmpegOptions...)
+	if profile.forceRG == true {
+		ffmpegArgs = append(ffmpegArgs,
+			// Set up ReplayGain processing
+			"-af", "volume=replaygain=track:replaygain_preamp=3dB:replaygain_noclip=0, alimiter=level=disabled",
+			// Drop redundant ReplayGain tags
+			"-metadata", "replaygain_album_gain=",
+			"-metadata", "replaygain_album_peak=",
+			"-metadata", "replaygain_track_gain=",
+			"-metadata", "replaygain_track_peak=",
+		)
+	}
+	ffmpegArgs = append(ffmpegArgs, "-f", profile.format, "-")
+
+	return exec.Command("/usr/bin/ffmpeg", ffmpegArgs...)
+}
+
+// Put special clients that can't handle Opus here:
+func detectFormat(client string) (profile string) {
+	if client == "Soundwaves" { return "mp3_rg"  }
+	if client == "Jamstash"   { return "opus_rg" }
+	return "opus"
+}
+
+// Generate cache key (file name). For, you know, encoded tracks cache.
+func getCacheKey(sourcePath string, profile string) (string) {
+	format := ENC_PROFILES[profile].format
+	return fmt.Sprintf("%x-%s.%s", xxhash.Sum64String(sourcePath), profile, format)
+}