<div>
Check out WM Converter Pro. See if that would help you.
</div>


<div>
You can use ffmpeg:<br />

<pre><code class="code-1 nolinks" id="code-20-41562187-1"><span>ffmpeg -i video.mp4 -vcodec copy -acodec ac3 -ab 128kb newvideo.mp4</span>
</code></pre>
<a href="https://trac.ffmpeg.org/wiki/Encode/HighQualityAudio" rel="ugc">https://trac.ffmpeg.org/wiki/Encode/HighQualityAudio</a>
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<div>
I would use Jan-Jannsen's suggestion. :)
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<div>
Could you provide an example of how I use this: <br />
<br />
ffmpeg -i video.mp4 -vcodec copy -acodec ac3 -ab 128kb newvideo.mp4<br />
<br />
Bear in mind I'm not familiar with the product nor am I a programmer
</div>


<div>
Try this if that is to complex. <br />
<br />
Oxelon Media Converter<br />
<br />
<a href="http://www.guidingtech.com/3138/oxelon-media-converter-is-a-multi-functional-audio-video-converter-for-windows/" rel="ugc">http://www.guidingtech.com/3138/oxelon-media-converter-is-a-multi-functional-audio-video-converter-for-windows/</a>
</div>


<div>
Do you have personal experience with Oxelon Media Converter? I ask because when I click on your link, it routes me to another product (Wondershare Video Converter Ultimate) which I already have.<br />
<br />
If I search and find the Oxelon Media Converter website, when I attempt to download it I get a warning it might cause harm to my computer
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<div>
Here is the download link. I downloaded it with no issues. My virus scanner picks up things quickly and I did not get any errors on this.<br />
<br />
<a href="http://www.oxelon.com/omc/oxelonmedia.exe" rel="ugc">http://www.oxelon.com/omc/oxelonmedia.exe</a>
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<div>
If you recall from my original question, my objective is to convert the audio portion of a video file from aac to ac3 without altering the video. I spent a fair amount of time with oxelon and do not find that capability. Maybe I'm missing something?
</div>


<div>
If that's the case then this is the one I found.... I did not get any errors or problems with this link.<br />
<br />
<a href="https://www.wondershare.com/convert-audio/ac3-to-aac.html" rel="ugc">https://www.wondershare.com/convert-audio/ac3-to-aac.html</a>
</div>


<div>
Do you really need the audio stripped out and converted to ac3? &nbsp;Would a straight demux to .aac work for you for expediency?<br />
<br />
Suggest you have a quick play with MP4Muxer<br />
(<a href="http://www.videohelp.com/download/mp4muxer-0.9.3.zip" rel="ugc">Direct Download Link</a>)<br />
<br />
Unzip and run the mp4muxer utility<br />
Drop your MP4 onto the larger window, switch to the Demultiplex tab, highlight the audio stream and press the Demultiplex button. &nbsp;By default it will put the .aac in the folder the .mp4 is in.<br />
<br />
The progress bar uses &quot;Microsoft Minutes&quot; so it will look like it's going to take an age to complete but it takes around a second for every 10 minutes of MP4 playback time.<br />
<br />
If you're going to automate this to just run through a whole folder of .mp4's and then collect up the audio files at the end then it might be better using the ffmpeg command line option already hinted at but adding a convert .aac to .ac3 stage will slow things up a bit.
</div>


<div>
MASQ: Sounds like exactly what I'm looking for, however, after downloading it and dropping the movie I want to convert in the large window, and it also brings in the acc audio track as you said, how do I convert it to ac3? I don't see that option.
</div>


<div>
It doesn't :(<br />
Demuxing simply splits out the audio and video streams that already exist. If you really need .ac3 you're going to have to run a second conversion. &nbsp;It's not a big deal but will mean two batches:<br />
<br />
1) Split out aac from all mp4's<br />
2) convert all the aac's to ac3's<br />
<br />
Stage 2 is the one that will take the time. &nbsp;Hence my original question - is there a reason for moving to .ac3 rather than sticking with the .aac's?<br />
<br />
The alternative is the ffmpeg route which does the same but combines the demux with the conversion so each file takes longer but the overall time for conversion of all the videos will be about the same.
</div>


<div>
The only reason is I'm finding players/movies not supporting aac. I draw that conclusion by watching some of my mp4 movies and discovering there is no surround sound. If I convert those same movies to ac3 they works perfectly. Maybe there's something else going on I'm missing, but it seems pretty straight forward to me. Unfortunately, for this kind of problem, I have a couple of thousand mp4's to deal with.<br />
<br />
I like the batch approach with ffmpeg but I'm not smart enough to know how to do that.
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<div>
But you're going to have to mix the AC3 back in with the video stream at the end just so you get better than 2.0 audio playback with your movie!<br />
<br />
This is starting to sound like a workaround where instead it might be possible to fix why your H.264/AAC isn't playing back 5.1 properly on your system and save all the effort of multiple conversion back &amp;&nbsp;forth to AC3.
</div>


<div>
To play mp4 HD you need a supporting sound card and up to date video card with a good video player and a couple of codecs to do the work in the media player,<br />
Update the drivers from your manufacturer not Microsoft.<br />
Which windows and which media player do you use?<br />
When you have problems with the newer high definition video audio sounds as if your running something outdated or getting old.<br />
<br />
The two codecs required I use even in windows 7 for support all video is ffdshow &nbsp;<a href="http://www.videohelp.com/software/ffdshow" rel="ugc">http://www.videohelp.com/software/ffdshow</a> and AC3 filter <a href="http://www.videohelp.com/software/AC3-Filter" rel="ugc">http://www.videohelp.com/software/AC3-Filter</a><br />
AC3Filter is a high quality free audio decoder and processor filter.<b> It allows media players to playback movies with AC3 and DTS audio tracks. </b>Also it can process any audio track<br />
Use the links BELOW the ADDS it's a dark line with<br />
Tool Description &nbsp;Type Rating Comment <br />
as &nbsp;the above is adds only where it says start &nbsp;download now <b>disregard,</b><br />
<a href="https://filedb.experts-exchange.com/incoming/2016/04_w18/1093324/ac3-filter.JPG" target="_blank" title="ac3 filter (126 KB)"><img alt="ac3 filter" class="file-block lazyload" style="max-width: 800px;" data-src="https://filedb.experts-exchange.com/incoming/2016/04_w18/800_1093324/ac3-filter.JPG" /></a><br />
Why not just use mp3 it gives a good sound when in stereo, once you alter the audio it gets pretty tricky and tiresome with the time and work load.<br />
Also it's worth mentioning changing the audio format from within a video may not produce the results you want as different video format use different audio formats, propriety.<br />
The audio format is insync with the video frames of that particular video format.<br />
Altering the audio only may cause it not to sync correctly with the video frames.<br />
<br />
I use youtube downloader pro <a href="http://www.ytddownloader.com/" rel="ugc">http://www.ytddownloader.com/</a>&nbsp;to convert the audio out only<br />
&nbsp;I believe the free version also works just fine, the pro version offers batch costs 29 dollar a year.<br />
first put it on convert tab&gt;then navigate to file&gt;or drag it onto this address bar slot<br />
Then in the convert to scroll down to mp3 if you dont want to cut or change the volume click on convert, note the destination out put, I have desktop<br />
It's very fast <br />
<a href="https://filedb.experts-exchange.com/incoming/2016/04_w18/1093320/convert-to-audio.JPG" target="_blank" title="convert to audio (155 KB)"><img alt="convert to audio" class="file-block lazyload" style="max-width: 800px;" data-src="https://filedb.experts-exchange.com/incoming/2016/04_w18/800_1093320/convert-to-audio.JPG" /></a>However you could easily convert the entire video to mp4 or avi thus changing audio as well within the video no out of sync issues for a better supported video yotube dowloader has a few video formats you can choose.<br />
mp3 can play reasonably well good sounds.<br />
<br />
Regards Merete
</div>


ac3-filter.JPG

convert-to-audio.JPG

<div>
Lots of good comments. Thanks. To digress a bit, I'm not watching movies on my Windows 10 laptop where switching driver options might be a possibility. Movies are stored on a Synology network drive running apps Plex and DS Video. On the viewer end I use the ROKU 4, also running Plex and DS Video.<br />
<br />
When I started converting a few years back, neither of those apps supported anything but stereo. Over time, with updates, now both claim support for AC3 and AAC so I started reconverting those same movies to AC3 from the ISO file I also store but this is a lengthy process. Somewhere along the reconversion path I noticed some titles were not playing surround. Only my 2 front speakers. After more googling I learned while AAC is a more advanced codec, it is not particular good at backward compatibility so I opted to discontinue the AAC reconversion and switched to the older, but known for good compatibility trying to avoid having to go back and reconvert everything a second time by looking for a product that just converts audio and not video with the hope that process would take less time.<br />
<br />
I agree, even if I find such a product there might be issues with video sync., but hoping that's not the case
</div>


<div>
You have my sympathy, I have a similar NAS/Plex/Roku setup, the 'droid boxes and even the older WDTV handle this much better!<br />
The difficult which you've already implied is reencoding without touching the video to reduce time.<br />
<br />
Will have a think. &nbsp;Suspect the solution is along the lines of:<br />
<br />
Either convert the whole thing but set the video to a ridiculously low quality so it's quick and then dump the video and reimport the ac3 conversion back to the original<br />
<br />
Or<br />
<br />
batch the files to export the aac keeping the file name<br />
then<br />
batch the files to convert all the exported .aac's to &nbsp;dd ac3 with same file name<br />
then<br />
batch the import/muxing of .ac3's to mp4's with same name<br />
<br />
that would give you mp4's with a choice of audio track, not sure if you can also set the preferred track option at the same time.<br />
<br />
sync shouldn't be an issue if you're maintaining fps through the conversions<br />
<br />
thinking ....
</div>


<div>
I've been testing a software named &quot;Freemake Video Converter&quot; which, on the surface, looks like the perfect product for doing what I need to do. It's free, although that's of little concern, but does convert the audio, leaving the video alone. Even better, it allows you to &quot;queue&quot; multiple movies. To date, I've loaded as many as 10 movies. It takes about 20 minutes to convert a 1080p aac to 1080p ac3. Far less than reconverting the entire video.<br />
<br />
So far, I've converted several movies and watched 2 with great surround playback and no evidence of sync problems. Hope that continues.
</div>


<div>
Thanks for the insight and comments
</div>


<div>
<div class="content wysiwyg-content">
I have a ton of video files all formatted h.264 mp4, aac audio. I'd like to find a converter capable of converting only the audio portion of the file to ac3, not modifying or re-converting the video. Does such a software even exist?<br />
<br />
The video conversion took 60-90 minutes for each one and I have 2000+ to work my way through so anything I use has to rip through the audio quickly.
</div>
</div>


I have a ton of video files all formatted h.264 mp4, aac audio. I'd like to find a converter capable of converting only the audio portion of the file to ac3, not modifying or re-converting the video. Does such a software even exist?

The video conversion took 60-90 minutes for each one and I have 2000+ to work my way through so anything I use has to rip through the audio quickly.

Audio Conversion of a Video file

Digital audio is technology that can be used to record, store, generate, manipulate, and reproduce sound using audio signals encoded in digital form. Following significant advances in technology, digital rapidly replaced analog audio technology in most areas. Digital audio systems may include compression, storage, processing and transmission components. It is important to distinguish between the audio coding format, the codec performing the encoding and decoding of the raw audio data, and the container file. Common file formats include .wav, .aiff, .au, .m4a, .mp3, .wma, .ra and .raw.

Digital Audio

Multimedia applications are those programs that integrate more than one media at a time; browsers are the most obvious. However, the term has come to include the use of programs that enable the use of any component that isn’t simple text and static graphics, such as audio, video, animation, virtual reality, conferencing and monitoring.