320 kbs mp3 to 6 channel ac3, does it make sense?

[deadrats]

as the title suggests, does it make any sense to convert either an mp3 audio file at a bitrate of 320 kbs to a 6 channel 320 kbs ac3? the reason i'm asking is because as i was playing around with ffmpeg (my new favorite "toy") i realized that i could take an audio file (most formats, but not aac) and convert it to a 6 channel ac3 file and to my ears it does sound like the audio was improved (it sounds "richer") but it could be my wishing it sounded better.

my gut feeling tells me that it should be possible to actually improve audio in this way as you can't add channels that don't exist, but i may be wrong.

so what do you guys think, does it make any sense to convert mp3 files to 6 channel ac3 files or are the percieved improvements a "head fake"?

[yoda313]

Personally I think "fake" surround isn't worth the time involved. Your digital amp probably has surround modes designed to do just that. You might want to fool around with those and see if they provide a satisfactory "surround" for you without any conversion.

Again that's just my personal take on it. Feel free to experiment but just don't expect it to sound like a hollywood dvd track from a stereo source.

[FulciLives]

I have read all kinds of different method of converting 2 channel Stereo to 5.1 AC-3 or DTS etc. and as yoda313 says it doesn't seem like it is worth the trouble because it seems that to do it proper you really need to do a lot of work.

I don't know how ffmpeg does it but somehow I feel it doesn't do it well considering all the complex things that should be done when attempting such a conversion (2.0 to 5.1) and even then the benefit is more a "head fake" as you say than anything else.

In any event if you do create 5.1 AC-3 then you should use a bitrate of 448kbps for best quality or at the very least 384kbps. Pretty much everyone is in agreement that anything less is not enough bitrate.

For instance almost all commercial DVD discs with 5.1 AC-3 use 448bkps and only once-in-a-blue moon will they use 384kbps. I've never seen less than 384kbps used for 5.1 AC-3 audio.

Now you might say, "but my source is only 320kbps" but you must remember that the source is also only 2 channels instead of 6 channels and since 6 channels is more information to encode than 2 channels ... well there you go ... more bitrate is needed.

Anyways I have seen a few threads over the years about 2.0 to 5.1 conversion but I haven't seen any in a long time so I can't point you to any threads other than to say that they exist and hopefully a forum search will turn them up.

- John "FulciLives" Coleman

[yoda313]

Actually one more thing to add to this is if your digital amp is new enough it might have Dolby Pro Logic 2. If it does this is supposed to take any sound source and make it into "5.1" surround sound. So if yours is less than 3 or 4 years old you probably of DLP2 and that would be the best option to get surround sound out of your nonsurround sound source. JUST AN FYI.

[guns1inger]

Unless you are going to take the time to break down the original and re-mix it for 5.1, even using something like the VI plugins, then it isn't worth it. Just telling ffmpeg to convert a 2 channel mp3 to a 5.1 AC3 isn't going to get you anything. An as pointed out, 320kbps is way too low for 5.1 AC3

[raquete]

@ all in this thread:
great posts and opinions!

@ deadrats
if you're interested and use adobe audition i post for you some scripts(or screenshots) to extract center and surrounds,is one valid test for 5.1 from stereo but take care...as guns1linger posted:

An as pointed out, 320kbps is way too low for 5.1 AC3

regards