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AC3 Audio Not Working


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#1 streammonkey

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Posted 19 April 2013 - 05:22 AM

I performed the following to convert an AVI MP3 media file into an MP4 AC3 file.  The video plays on the Roku using Direct Play without an issue, but the audio isn't present.  When I play the video using VLC, the audio and the video are fine.  Any ideas why the audio is missing on the Roku?

 

1) Use MP4Box GUI - http://www.videohelp...s/My-MP4Box-GUI to demux the video/audio streams.
Limitation:  This program does not let you convert the audio stream.  So, if it is not AC3, I cannot use the audio "as is" for the Roku as it requires AC3 in an MP4 container.

 

2) Use ffmpegGui - http://www.videohelp...tools/ffmpegGUI to convert the demuxed MP3 stream to AC3.

 

3) Use MP4Box GUI to mux the video and newly converted AC3 into an MP4.

 

Here's the mediainfo on the file:

 

Video
ID                                       : 1
Format                                   : MPEG-4 Visual
Format profile                           : Advanced Simple@L5
Format settings, BVOP                    : Yes
Format settings, QPel                    : No
Format settings, GMC                     : No warppoints
Format settings, Matrix                  : Default (H.263)
Codec ID                                 : 20
Duration                                 : 52mn 59s
Bit rate mode                            : Variable
Bit rate                                 : 1 757 Kbps
Maximum bit rate                         : 8 415 Kbps
Width                                    : 688 pixels
Height                                   : 384 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 25.000 fps
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Compression mode                         : Lossy
Bits/(Pixel*Frame)                       : 0.266
Stream size                              : 666 MiB (90%)
Writing library                          : XviD 1.1.2 (UTC 2006-11-01)
Encoded date                             : UTC 2013-04-19 05:01:44
Tagged date                              : UTC 2013-04-19 05:02:20

 

Audio
ID                                       : 2
Format                                   : AC-3
Format/Info                              : Audio Coding 3
Mode extension                           : CM (complete main)
Format settings, Endianness              : Big
Codec ID                                 : ac-3
Duration                                 : 52mn 58s
Bit rate mode                            : Constant
Bit rate                                 : 192 Kbps
Channel(s)                               : 2 channels
Channel positions                        : Front: L R
Sampling rate                            : 48.0 KHz
Bit depth                                : 16 bits
Compression mode                         : Lossy
Stream size                              : 72.8 MiB (10%)



#2 streammonkey

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Posted 19 April 2013 - 06:22 AM

Seems that the Roku does not support AC3 as it worked perfectly fine once I converted the MP3 stream into AAC using the following technique.

 

1) Use LameXP - http://www.videohelp.com/tools/LameXP to convert the MP3 stream to AAC.

Note:  You must also download the Nero AAC Codec - http://www.videohelp.../Nero-AAC-Codec and place the three files in the LameXP program folder.

 

2) Use MP4Box GUI to mux the video and newly converted AAC into an MP4.

 

 

If anyone knows of an easier way to convert an AVI MP3 into an MP4 AAC, I would greatly appreciate it.



#3 streammonkey

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Posted 19 April 2013 - 06:55 AM

Ok, here's the final solution.

 

1) Use MKV / AVI 2 MP4 - http://www.videohelp.../mkv-avi-to-mp4 to convert the MKV or AVI into an MP4 AAC.

 

Note: You must also download the Nero AAC Codec - http://www.videohelp.../Nero-AAC-Codec and place the three files in the same folder to which you unzipped the MKV / AVI 2 MP4 program.

 

This "all-in-one" tool seems to work really well.  In addition, unlike the standalone audio conversion programs mentioned earlier, this program takes the audio settings from the source file and passes them through with the exact same bitrate etc. to the final AAC.  The other programs required you to enter the bitrate values which required using mediainfo to see what they were.

 

However, if anyone knows of a better way to convert both MKV and AVI to MP4 AAC, please let me know.



#4 schuyler

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Posted 19 April 2013 - 04:27 PM

FYI, the Roku only supports AC3 in passthru mode, which means that it will only work if your Roku is connected via HDMI to something that understands AC3, usually a receiver. So if you're not using surround sound, you're better off with AAC.



#5 streammonkey

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Posted 19 April 2013 - 04:34 PM

FYI, the Roku only supports AC3 in passthru mode, which means that it will only work if your Roku is connected via HDMI to something that understands AC3, usually a receiver. So if you're not using surround sound, you're better off with AAC.

Ok, I see now.  So that's why it is recommended to have both the AAC and AC3 passthru streams when encoding for Roku so that you get AAC when not connected through a receiver and AC3 when you are, right?



#6 schuyler

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Posted 19 April 2013 - 04:39 PM

Yep! Using both a stereo AAC track and a 5.1 AC3 track gives you the best chances of being able to play the file anywhere, including the future world where you've got surround sound everywhere.



#7 streammonkey

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Posted 19 April 2013 - 05:19 PM

Yep! Using both a stereo AAC track and a 5.1 AC3 track gives you the best chances of being able to play the file anywhere, including the future world where you've got surround sound everywhere.

The MKVAVI2MP4 (http://sourceforge.n...cts/mkvavi2mp4/) program I mentioned seems to put everything into an AAC track.  Can 5.1 audio be put into an AAC track?  If so, will the Roku be able to use it if the Roku is connected to a 5.1 receiver?



#8 schuyler

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Posted 19 April 2013 - 05:31 PM

There is such a thing as 5.1 AAC, but the Roku doesn't support it. AAC for stereo, AC3 for surround sound.



#9 streammonkey

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Posted 25 April 2013 - 02:34 AM

Is AC3 stereo supported just as well as AAC stereo?

 

Also, if I have both an AAC Stereo and an AC3 5.1 Passthrough track, do I have to set my Roku to 5.1 audio in order for the AC3 5.1 track to be used or are both tracks always available so that whatever the Roku is plugged into (i.e. Receiver or TV) can use whichever track is compatible with it?



#10 schuyler

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Posted 25 April 2013 - 04:53 AM

Stereo AC3 is only supported if it's passed through to a receiver that can process it (receivers will typically display PLII for this). Basically, the only thing that the Roku understands and can deal with on its own is stereo AAC. If it's connected to a receiver, it can also pass through AC3.

 

You have to put your Roku into the 5.1 mode for it to send that track over HDMI. I'm not an expert on HDMI, but think of it as sending audio and video in its own format. It doesn't send the original file over HDMI, the Roku has to take the original and then send the video and audio in the way that the HDMI spec dictates. So the Roku has to choose a particular audio stream to pass along, it can't send both.



#11 streammonkey

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Posted 25 April 2013 - 02:52 PM

I performed a quick test using a TV that I know will not convert digital 5.1 to stereo (i.e. no sound when Roku directly connected and only track is 5.1).  I used a video file that had AAC Stereo and AC3 5.1.  I set the Roku audio to 5.1.  The audio was present on the TV.  So, it seems that Roku definitely sends the AAC track when audio is set to 5.1.  I need to get an HDMI to optical converter as my receiver doesn't have HDMI IN so that I can confirm that the 5.1 track is also being sent.



#12 destructo

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Posted 25 April 2013 - 11:28 PM

For best results when testing, create a test file from a DVD or blu-ray. Make sure you have aac stereo and AC3 5.1 audio tracks, but use a foreign audio or commentary track for stereo. This way you know which track is playing when you test and troubleshoot.

destructo
Rokoding: roku.yt1300.com

 


#13 streammonkey

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Posted 26 April 2013 - 02:56 AM

For best results when testing, create a test file from a DVD or blu-ray. Make sure you have aac stereo and AC3 5.1 audio tracks, but use a foreign audio or commentary track for stereo. This way you know which track is playing when you test and troubleshoot.

Great idea.  Also, my receiver has a blue indicator light and display that shows which speakers are being accessed by the incoming signal.  So, hopefully I'll know whether or not the 5.1 channel is being used.



#14 streammonkey

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Posted 28 April 2013 - 08:21 PM

I'm using XMedia Recode to re-encode the 5.1 stream into an AAC stereo and an AC3 5.1 track.  However, I just noticed that Handbrake has an actual AC3 passthru setting whereas XMedia Recode only has an AC3 and an E-AC3 setting.  Does anyone know if this means that the AC3 5.1 tracks I create using XMedia Recode will not work on the Roku for passing through 5.1 audio to my receiver?



#15 Curbob

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Posted 28 April 2013 - 09:40 PM

I had this problem today and found on the roku 3 (not sure about others) that you can choose play options and then transcoding and choose transcode, you can then play transcoded and the audio works



#16 streammonkey

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Posted 28 April 2013 - 10:42 PM

I had this problem today and found on the roku 3 (not sure about others) that you can choose play options and then transcoding and choose transcode, you can then play transcoded and the audio works

True.  However, I want to be able to Direct Play all of my media.






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