Why doesn't my ATV1 like 640kbps AC3/DD audio?

Discussion in 'Video Streaming Boxes & Services' started by Matt_C, Nov 28, 2010.

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  1. Matt_C

    Matt_C
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    Apart from not being able to output multichannel AAC audio (as obviously my AVR doesn't decode multichannel AAC, only AC3 and DTS) I haven't had any problems with audio tracks playing from XBMC on my ATV1 - I've even got an old DVD rip outputting Pro Logic!

    However, one it does seem to struggle with, is AC3 @ 640kbps! Don't know why, but it just doesn't like it - makes the multichannel light on the front of my AVR go mental and the sound is flitting between on and off rapidly (as in signal > no signal > signal > no signal, etc as far as the AVR is concerned)

    Don't know why? Restriction of AVR or ATV? Can't be the AVR surely, as the original DVD with the 640kbps DD track plays fine? Likewise, burn the video file to DVD disc, it plays fine from the DVD player. Guess it must be the ATV?
     
  2. Matt_C

    Matt_C
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    Actually, I tell a lie - the video file I have with multichannel AAC is being output to my AVR as DD 5.1!!! :eek:

    It's never done this before, so must be something new in the SVN version of XBMC that's on there.

    However, it is, now and again, having issues with that also - same thing of flashing on and off on the amp. It's a lot better than the 640kbps AC3; it's only doing it when the audio goes quiet like there is no constant sound...

    Curiouser and curiouser...
     
  3. Matt_C

    Matt_C
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    Also worth noting - not all the 640kbps AC3 tracks play badly. I have Batman in 720p mkv, with a 640k AC3 track and that plays fine. But Predators (720p mkv) with 640k AC3 stutters like hell (audio stutter, not video), same with Labyrinth (720p mkv / 640k AC3)
     
  4. CrispyXUK

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    Remux them into an mp4 and play via the ATV interface.
     
  5. Matt_C

    Matt_C
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    No point remuxing to MP4 - it has no problem with the mkv container. It just doesn't seem to like *most* 640kbps AC3 audio tracks. I re encoded one last night, from AAC 6ch to AC3 6ch and told it to encode @ 640k - didn't like it at all. So I'm redoing it @ 448k which is should like

    And I don't like using the stock ATV interface - the whole point of getting the old ATV was to use XBMC on it ;)
     
  6. next010

    next010
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    XBMC (Dharma) has a built in audio transcoder it converts AAC 5.1 into Dolby AC3 5.1 audio. As to the audio issues cant say for certain could be bugs, the guys on the XBMC forums may be able to identify the problem more if you provide them with the XBMC debug logs.

    There appear to be issues with audio under the ATV and current builds as my mkv files with flac audio kill the sound system altogether.
     
  7. Matt_C

    Matt_C
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    Had the same issues with some files (that had 640k AC3) on the ATVFlash install of XBMC too (9.11). Interestingly, my PC also didn't like 640k AC3 either....

    That's really cool Dharma has a built in transcoder for audio. Just a shame it doesn't really work lol
     
  8. next010

    next010
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    Could it be your audio encoder ?

    Try encoding with eAC3to and see what happens. Only works under Windows I'm afraid.

    Download eaC3to + the eac3toGUI, plus you'll need MKVmerge but I assume thats installed already.

    * After running eAC3toGUI make sure the source paths to exe files are correct.
    * Click "add source file" and point it at your mkv
    * Click on "eac3toaudio" tab
    * Under "input files or folders" select from the drop down box the file you inputted
    * Under "file name" give a title like newaudio
    * Under "save as type" select ac3
    * Click "run command line tab specific"

    What this will do is extract the audio from the mkv file then convert the audio. After this process is complete start MKVmerge drag and drop the new audio and original mkv into it then deselect the original ac3 audio track and mux a new MKV file from it.
     
  9. next010

    next010
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    Just a slight update to this, there appears to be a bug/problem with XBMC if the audio output it set to HDMI when running on the ATV with the current builds, that is why AAC/Flac audio output can kill the sound system.

    Simply changing the audio output in the system settings to optical/coax resolves it even if your using HDMI passthru, might be worth a try in your case Matt_C.
     
  10. Matt_C

    Matt_C
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    I've only ever had it on optical/coax, and I don't use HDMI passthrough (as HDMI only goes from the ATV to the TV, so is pointless for audio for me)

    As for the encoder - I'm not originally encoding them, so I can't say for sure what encoder is being used. But I have noticed that if I encode something as AC3 640k in Handbrake, the ATV/XBMC still doesn't like it. So I usually re-encode to 448, or even 512, to avoid this....
     

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