api: Added api converter for video to mp3 data.

The current implementation is weak and a wip which calls the ffmpeg executable to convert video data to mp3 files.

api/apiconv.go

@@ -0,0 +1,76 @@
+// Copyright 2017 YTD Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+// apiconv: Converts Decoded Video data to MP3, WEBM or MP4.
+// NOTE: To reimplement using Go ffmpeg bindings.
+package api
+
+import (
+	"errors"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+)
+
+//Converts Decoded Video file to mp3 by default with 123 bitrate or to
+//flv if otherwise specified and downloads to system
+func APIConvertVideo(file string, int bitrate, url string, decVideo []byte) (io.Writer, error) {
+	cmd := exec.Command("ffmpeg", "-i", "-", "-ab", fmt.Sprintf("%dk", bitrate), path)
+	stdin, err := cmd.StdinPipe()
+	if err != nil {
+		logrus.Fatalf(err)
+	}
+	if filepath.Ext(file) != ".mp3" && filepath.Ext(file) != ".flv" {
+		file = file[:len(file)-4] + ".mp3"
+	}
+
+	logrus.Infof("Converting video to %q format", filepath.Ext(file))
+	if filepath.Ext(file) == ".mp3" {
+		// NOTE: To modify to use Go ffmpeg bindings or cgo
+		_, err = exec.LookPath("ffmpeg")
+		if err != nil {
+			logrus.Errorf("ffmpeg not found on system")
+		}
+
+		cmd.Start()
+		logrus.Infof("Downloading mp3 file to disk %s", path)
+		cmd.Write(decVideo) //download file.
+
+	} else {
+		cmd, err = os.Create(path)
+		if err != nil {
+			logrus.Error("Unable to download video file.", err)
+		}
+		err = apiDownloadVideo(url, cmd)
+		return err
+	}
+
+	return nil
+}
+
+//Downloads decoded video stream.
+func APIDownloadVideo(videoUrl, cmd io.Writer) error {
+	logrus.Infof("Downloading file stream")
+
+	resp, err := http.Get(url)
+	if err != nil {
+		return fmt.Errorf("requesting stream: %s", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != 200 {
+		return fmt.Errorf("reading answer: non 200 status code received: '%s'", err)
+	}
+	length, err := io.Copy(out, resp.Body)
+	if err != nil {
+		return fmt.Errorf("saving file: %s (%d bytes copied)", err, length)
+	}
+
+	logrus.Infof("Downloaded %d bytes", length)
+
+	return nil
+}