Enhance progress extraction

lib/processor.js

@@ -523,7 +523,7 @@ module.exports = function(proto) {
               }
 
               stderrRing.callback(function(line) {
-                utils.extractProgress(self, stderrRing.get(), duration);
+                utils.extractProgress(self, line, duration);
               });
             }
           }

lib/utils.js

@@ -320,18 +320,12 @@ var utils = module.exports = {
    * Extract progress data from ffmpeg stderr and emit 'progress' event if appropriate
    *
    * @param {FfmpegCommand} command event emitter
-   * @param {String} stderr ffmpeg stderr data
+   * @param {String} stderrLine ffmpeg stderr data
    * @param {Number} [duration=0] expected output duration in seconds
    * @private
    */
-  extractProgress: function(command, stderr, duration) {
-    var lines = stderr.split(nlRegexp);
-    var lastline = lines[lines.length - 2];
-    var progress;
-
-    if (lastline) {
-      progress = parseProgressLine(lastline);
-    }
+  extractProgress: function(command, stderrLine, duration) {
+    var progress = parseProgressLine(stderrLine);
 
     if (progress) {
       // build progress report object