diff --git a/src/FFMpeg/Filters/Waveform/WaveformRatioFixerFilter.php b/src/FFMpeg/Filters/Waveform/WaveformRatioFixerFilter.php
index ec40205..368b6bd 100644
--- a/src/FFMpeg/Filters/Waveform/WaveformRatioFixerFilter.php
+++ b/src/FFMpeg/Filters/Waveform/WaveformRatioFixerFilter.php
@@ -41,19 +41,13 @@ class WaveformRatioFixerFilter implements WaveformFilterInterface
         $dimensions = null;
         $commands = array();
 
-        foreach ($waveform->getVideo()->getStreams() as $stream) {
-            if ($stream->isVideo()) {
+        foreach ($waveform->getAudio()->getStreams() as $stream) {
+            if ($stream->isAudio()) {
                 try {
                     
-                    // Get the dimensions of the video
-                    $dimensions = $stream->getDimensions();
-                    
                     // If the downmix parameter is set to TRUE, we add an option to the FFMPEG command
-                    if(!$this->downmix) {
-                        $commands[] = '"showwavespic=s=' . $dimensions->getWidth() . 'x' . $dimensions->getHeight().'"';
-                    }
-                    else {
-                        $commands[] = '"aformat=channel_layouts=mono,showwavespic=s=' . $dimensions->getWidth() . 'x' . $dimensions->getHeight().'"';
+                    if($this->downmix == TRUE) {
+                        $commands[] = '"aformat=channel_layouts=mono"';
                     }
                     
                     break;
diff --git a/src/FFMpeg/Media/Waveform.php b/src/FFMpeg/Media/Waveform.php
index feb26b3..e34f564 100644
--- a/src/FFMpeg/Media/Waveform.php
+++ b/src/FFMpeg/Media/Waveform.php
@@ -26,7 +26,7 @@ class Waveform extends AbstractMediaType
     private $width;
     private $height;
 
-    public function __construct(Video $video, FFMpegDriver $driver, FFProbe $ffprobe, $width, $height)
+    public function __construct(Audio $audio, FFMpegDriver $driver, FFProbe $ffprobe, $width, $height)
     {
         parent::__construct($video->getPathfile(), $driver, $ffprobe);
         $this->video = $video;