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Transcoded audio sounds wrong


jfarre20
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Transcoded audio sounds wrong, almost like reverse stereo. I can't really explain it. 

 

This happened before a long time ago on 3.0.5238.39498, and it went away with an update. 

 

I just noticed that its doing it again on 3.0.5724.3

 

I don't want to make a new video, so I will link my old one. I just tested the video file featured in my example clip and it's back to sounding wrong.

 

See video: 

 

https://www.youtube.com/watch?v=vIiFOblQ6UA 

 

 

Media info for the source file that was demonstrated in the video I linked - as detected by media-browser:

 

(avi)

  <streamdetails>
      <video>
        <codec>mpeg4</codec>
        <micodec>mpeg4</micodec>
        <bitrate>826041</bitrate>
        <width>624</width>
        <height>352</height>
        <aspect>16:9</aspect>
        <aspectratio>16:9</aspectratio>
        <framerate>23.97602</framerate>
        <scantype>progressive</scantype>
        <default>False</default>
        <forced>False</forced>
        <duration>49</duration>
        <durationinseconds>2951</durationinseconds>
      </video>
      <audio>
        <codec>mp3</codec>
        <micodec>mp3</micodec>
        <bitrate>128000</bitrate>
        <scantype>progressive</scantype>
        <channels>2</channels>
        <samplingrate>48000</samplingrate>
        <default>False</default>
        <forced>False</forced>
      </audio>
    </streamdetails>
  </fileinfo>

Media info for the video I tried to play today that had the same audio issue:

 

(mkv)

<streamdetails>
      <video>
        <codec>h264</codec>
        <micodec>h264</micodec>
        <bitrate>3451213</bitrate>
        <width>1280</width>
        <height>720</height>
        <aspect>16:9</aspect>
        <aspectratio>16:9</aspectratio>
        <framerate>23.97602</framerate>
        <scantype>progressive</scantype>
        <default>True</default>
        <forced>False</forced>
        <duration>21</duration>
        <durationinseconds>1277</durationinseconds>
      </video>
      <audio>
        <codec>aac</codec>
        <micodec>aac</micodec>
        <language>eng</language>
        <scantype>progressive</scantype>
        <channels>2</channels>
        <samplingrate>48000</samplingrate>
        <default>True</default>
        <forced>False</forced>
      </audio>

As you can see, there's no correlation between the two formats. However, some video files exhibit this issue while others do not. 

 

 

All play fine from WMP/VLC/MPCHC/Direct Playback in chrome.

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It affects anything that requires transcoding, web client, android, win8 app, etc. I primarily use the web client.

 

I'll attach a few seconds of the original file, and the transcoded file from the transcoding-temp directory.

 

embytranscodeaudioissue.zip

 

 

Due to filesize constraints, I have the transcoded video at 1mbps 480p, but the audio quality sounds the same even at 30mbps 1080p.

Edited by jfarre20
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The transcoding temp files sound wrong.

 

If you are having trouble hearing it, use headphones.

Edited by jfarre20
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  • 2 weeks later...
CharlieC3

I am also hearing strange audio. I'm a Plex user looking to make the switch to Emby, so I recently installed it on my FreeNAS server through the Emby plugin and am testing it out. Transcoded TV and Movie stereo audio sounds different on Emby than it does through Plex, or when played locally via VLC. It's difficult to explain, it sounds like it might be reversing the audio like jfarre20 said above, but I just can't nail it. If you have a file of a show or movie outputting in stereo audio, you can test it by listening to a scene in VLC, then listening to the same scene in Emby. It's most obvious in scenes with clear spoken dialogue, very hard to miss.

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I'm glad I am not the only one having this issue. 

 

On further analysis of the audio issue, it seems like the left and right audio tracks may be slightly out of sync - causing it to sound like what I initially thought was reverse stereo. 

 

This is more of a ffmpeg issue than an emby issue.

Edited by jfarre20
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CharlieC3

This is more of a ffmpeg issue than an emby issue.

 

Looks like you might be right, the changelog for their Github release mentions that they started using a new version of ffmpeg

https://github.com/MediaBrowser/Emby/releases/tag/3.0.5724.3

 

Here's the last time the ffmpeg version was bumped, back in July:

https://github.com/MediaBrowser/Emby/commit/fe75e4ff3b65751789e14ae68a5fc50e98161a24#diff-33b00eb1f44df4bed303de1481369ccbR122

 

I'm a new Emby user, so I can't speak for it back then, but have you noticed this sound issue that far back?

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Next release will update it again for the new hardware decoding features. In the meantime you can always try manually downloading ffmpeg from zeranoe and replacing the boundaries

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I'm a new Emby user, so I can't speak for it back then, but have you noticed this sound issue that far back?

 

The YouTube video clip that I attached in my first post is from the first time I noticed this - back in May of 2014.

 

That same clip's sound was fixed after one of the server updates that occurred after May 20th 2014 but before Sept 11 2015. After Sept 11, I noticed it sounded wrong again.

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CharlieC3

Seems like this is a recurring issue with the codecs used. I'm no C# dev, but this would be one valuable functional test to have handy in the Github project :)

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