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audio encoding options

Posted: Thu Jul 29, 2010 5:21 am
by cowboyup910
I looked at the Guide for Handbrake about the Audio options for encoding, but I was wondering if someone could simplify it a little for me, if possible.

Audio codec by default in version 0.9.4 is AAC (faac). I noticed under the drop down AC3 Passthru. What's the difference really? Also theres a section called Mixdown. Some titles I ripped, the audio plays back low, my speakers are turned all way up but I have trouble hearing the speech, but events like bombing or shooting are scary loud. Do you know what I am referring too, does that make sense?

Some DVD's contains different audio tracks, which one should I use, or is it best to just leave on automatic?

If you have any questions please ask?

Thanks in Advance,

Windows User Here!

Re: audio encoding options

Posted: Thu Jul 29, 2010 12:11 pm
by randomreuben
Dear cowboyup910,

Let me see what I can do.

1. AC3 is the DVD's original audio track. Usually, this is a very large file (hundreds of MB on a long movie) and is usually necessary only if you find yourself using a home theater system or speaker set capable of putting out 5.1 audio. 5.1 audio is five speakers and a subwoofer (the big box that puts out the "boom" sounds).

2. AAC is the name for a lossy audio codec. What x264 does for your video (i.e. crush it down to a more manageable size while making it still look good) is what lossy audio codecs (of which AAC is one) does for your audio. AAC/MP3/Ogg Vorbis are all lossy codecs and you have the option of selecting any of these. If you want your audio to sound good, you need to be encoding at a bitrate above 160 kbps. 192 kbps is a great place to start and few people can actually tell a difference above that mark.

3. The difference in loud and soft sounds is based off cues found in your AC3 track. This is called the dynamic range of your audio. The dynamic range is what tells your player the difference between the loud (explosions) and the soft (conversations) parts. If you own Cyberlink PowerDVD, you will notice that in the audio configuration tab, you get to select between "Quiet", "Normal" and "Loud" (I think is the third option) for your audio output. What this means, is that PowerDVD is going to change the dynamic range between the loud and the soft sounds based on your settings. It gets this information from the AC3 file itself. Which brings us to point 4.

4. You can change the difference you hear between the loud and the soft sounds by changing the control called "DRC". If you set this sliding value to 1.0, you are getting what would be the "Normal" loudness option on PowerDVD. This is a good setting to leave it to, but you can change that to your liking.

5. Mixdown is what is useful if you don't have a 5.1 speaker system. 5.1 AC3 is going to be a much larger audio track than 2.0 (stereo) MP3. This is because the 5.1 AC3 audio track literally contains information for six different speakers (six speakers because there are five normal speakers and one subwoofer) and that makes for a large file. This sort of audio track is only useful if you need to output the sound to a 5.1 system that you own. If you downmix (the same as mixdown) to 2.0, which is what two speakers are (think headphones, your typical TV speakers, stereo system, anything with two speakers), the information that used to be spread out over six speakers now gets put into an output suitable for two speakers.

6. The benefit of downmixing to a 2.0 output, especially if you only have two speakers anyway, is that you save a lot of space and it sounds just as good. If you don't do it now and you only have two speakers, your movie player is going to do it for you anyway, if you only have two speakers. Now on this point, if you have a 5.1 speaker system and you want to save some space, you can encode your movie using the 5.1 information using the AAC and (I think) Vorbis codecs too. You can't on MP3.

7. Lastly, choosing between AAC, Vorbis and MP3 is not a simple matter. Choose AAC if you are going to encode to an MP4 container and play it back on certain devices (PSP, PS3 and certain hardware media players and Quicktime). Choose Vorbis if what you're after is a 5.1 encode with an MKV container (plays just fine on VLC media player). Choose MP3 if you have a 2.0 system and are encoding to an MKV container (plays fine on my WDTV and VLC).

These are the audio settings I use. You are free to choose your own, but I enjoy these a lot and I think you may like them. Set output codec to MP3, set Mixdown to Stereo (2.0), set bitrate to 192 kbps and set the DRC to 1.0. Leave everything else alone.

There are a lot of things to take in here and nothing attracts opinion like audio quality (you can see that I have an opinion on that myself). What is important is that unless there is a logical reason, e.g. device incompatibility, to switch audio codecs and settings, you should choose the one you are happy with.

All the best,


Re: audio encoding options

Posted: Thu Jul 29, 2010 3:45 pm
by mkelley
Let me provide information on why the speech is hard to hear but the other stuff is not (and to disagree with the previous poster).

With 5.1 surround sound the center channel carries the dialog, the left and right carry music and sound FX (and FX are also carried by the LR Rear speakers). In a surround sound system you can easily adjust things so the dialog is at the right level, but if you play it as a stereo track it will nearly always be a problem if the track is authored properly, no matter what reuben suggests you do (there's no good way to mixdown a 5.1 track that will keep speech clear unless you can actually surpress or boost some channels).

The best thing to do is get a surround sound system, because that's what the 5.1 track is designed for. Anything else is not going to sound as well, period. Otherwise try and find a track that is stereo only to use.

Re: audio encoding options

Posted: Thu Jul 29, 2010 5:35 pm
by randomreuben
mkelley is right of course, but it does boil down to what you can put up with. I live in an apartment with poor sound insulation and living harmoniously with neighbours here means a 2.0 stereo track for my headphones. You may be perfectly happy with a 2.0 downmix audio track. Ideally, I would have my den in a house's basement with carpeting and cushions to reduce reverberations and my AC3 audio on a 5.1 system, but because of how things are right now, a 2.0 is just the ticket. mkelley's suggestion is something I use myself. If offered a choice between a 5.1 track or a 2.0 track to select from (and most DVDs offer a downmixed audio track) I pick the 2.0 track from which to encode to an MP3.

Just to be clear again, I think mkelley's suggestions are the ideal solution. 5.1 AC3 audio on a surround system is always going to sound better than a 2.0 downmix, but if you are happy with the downmixing results, you can save yourself some space and get a decent encode.

Re: audio encoding options

Posted: Thu Jul 29, 2010 7:11 pm
by cowboyup910
PERFECTLY! Exactly the type of information I was looking for. Thank you all, randomreuben for explaining the basic parts of all this, information I was lacking. I think I need some speakers, I got Logitech X-540 5.1 Speaker System but I only have the two front, center(high above me on the wall) and subwoofer speakers connected. i think my settings are all screwed up in Vista, and thats why just in normal DVD playback I too sometimes have trouble hearing the audio. Myabe I need to get me more basic 2 speakers setup.

Again, Thank you!

Re: audio encoding options

Posted: Thu Jul 29, 2010 7:44 pm
by randomreuben

1. Hook up all of your speakers.
2. Let Vista or whatever soundcard software you have control your output.

Re: audio encoding options

Posted: Thu Jul 29, 2010 8:55 pm
by cowboyup910
I was about to pull those two speakers to install them but first I was messing with the configuration, trying to set speaker settings to 5.1 instead of the 7.1 that was checked. It wouldn't work, so I just uninstall using add/remove the driver. After the reboot i got no audio (of course) but i thought it would load Microsoft universal audio driver, so I reinstall the driver Vista, Windows7 Driver (32bits) Driver only (ZIP file) R2.50 and after the reboot still no sound. Goes to show you for messing with things.

Oh well guess I have to do a system image recovery, gl Macrium