Which is better AC3 (5.1) or MP3 on 2.1 speaker system?

[=CrAzYG33K=]

Which type of Audio should I have in my AVI file if I'm watching the AVI file in a stand-alone DivX player in a 2.1 speaker system? AC3 5.1 channel audio or MP3 audio??

[guns1inger]

If you are converting from DVD and space isn't an issue, AC3. Converting to MP3 will compress the audio, kill the surrounds, and is a poor substitute. Your Divx player will have to convert it to PCM anyway on the way out.

[=CrAzYG33K=]

If you are converting from DVD and space isn't an issue, AC3. Converting to MP3 will compress the audio, kill the surrounds, and is a poor substitute. Your Divx player will have to convert it to PCM anyway on the way out.

No - i'm specifically asking which audio will be better on a '2.1 Speaker system not 5.1'

[whitejremiah]

i'd personally run with 5.1...it is downconverted anyhow, and if you ever were to say want to restore it back to dvd form, you could do so without losing audio quality.....there is something around now called aud-x that may be worth looking into though, i havent toyed around with it in my standalone, but it looks promising......

[guns1inger]

Regardless of speaker system, a 5.1 AC3 mix is much better than anything MP3'd.

[whitejremiah]

that is true...is there any particular filesize your attempting to aim for? are you trying to squeeze a full movie onto a cdr? are you trying to squeeze a certain number of movies onto a dvdr? how long are the moives your trying to convert? there's a lot of things to think about, but yes, your definately better off keeping the 5.1 if at all possible, besides completly throwing out channels alltogether, mp3'ing the audio does also degrade the quality some (or if you compress it too much, a LOT) personally, i try to aim for around 1/3 dvdr and retain the ac3 audio myself when i do divx backups...well for most movies anyhow...animated stuff i generally go around 1/4dvdr and longer movies, i will go right up to 1.99gb (you cant go above 2gb or else you start having problems burning the files......)

[=CrAzYG33K=]

OK but an audio stream built for a 5.1 ie. 5 speakers wouldn't sound crap on a 2.1 setup??
I mean - wouldn't the AC3 sound kinda low in voice and have higher volume (decibel) during special effects?

[guns1inger]

Why ? By default, all DVD players can mix down 5.1 to stereo PCM. Many discs with 5.1 mixes have very little if anything in the lFE channel, relying on the amp to use frequency cutover to redirect LFE to the sub. Depending on the software and how it mixes down, you will simply get a stereo mix down from the 5.1, and either the original LFE or a cutover LFE going to the .1.

Unless you are going to take your 5.1 channels and do a special mixdown of the audio yourself, adjusting levels etc to make it sound how you want, why would you MP3 mix down sound better. That is without taking into account just how poor MP3 compression is for stereo. At least the original mix retains it's stereo seperation correctly. MP3, especially below around 256kbps, muddies and garbles stereo seperation. Given a choice, I would not touch MP3 with a very long barge pole if AC3 was available.

[RabidDog]

AC3 5.1 sound is the de-facto sound found on all movie discs . So when you play back any std DVD your existing setup is already "converting" 5.1 to 2.1. Conversion of the sound to mp3 only really makes sense if you are short of DVD space because however well you convert it, it will be degraded in quality. On many/most dvds there is already a seperate AC3- 2.0 sound track which can be used to save space, (just make sure its not the director going "yadadadada.. and then ...Blah blah blah.. and of course...Yada blah yada yada ..drone")

[adam]

No =CrAzYG33K= actually has a valid point. 5.1 AC3 downmixed to 2.0 results in too great a dynamic range. Once you adjust the dialogue to its proper volume (how you set volume) the louder parts of the film like explosions and such can literally blow your speakers. Turn those down and now you can't even hear what people are saying. In other words, the lows are too low and the highs are too high. Try it, its very noticable. This is why 2.0 tracks are included on DVDs, that and the fact that some players or receivers might not do the best quality downmix. This is also why many dvd players include a dynamic range compression option. If you have such an option then definitely stick with the 5.1 and just compress the dynamic range yourself.

If you don't have dynamic range compression on your player than I'd actually say that yes, the 2.0 mp3 will sound better assuming a high enough bitrate. Its an imperfect solution. You are using lossy compression so quality is always lost. But listening to an uncompressed (dynamic range that is) 2.0 downmix is just not an option in my opinion. You will constantly be adjusting the volume throughout the movie.

[=CrAzYG33K=]

ahhh.. finally someone who agrees ! (adam, here)
OK - pretty much of tech talk (most of which i din't get fully), but finally the point was driven home... Nice explanation adam. thanx.

[OldAmateur]

So, apparently, =CrAzYG33K= already knew the one acceptable answer before he posted his question. Why bother posting, then?

[=CrAzYG33K=]

So, apparently, =CrAzYG33K= already knew the one acceptable answer before he posted his question. Why bother posting, then?

uh .. no offense.. but, I really saw a change in sound effects between the 2 after I created this thread.. I, however, appreciate and accept all your views! 8)