avi-mpg, is it worth converting audio on an avi file from mp3>wav>ac3

[mub6]

hi guys,
im using tmpgenc plus to encode my avi file (which has mp3 audio) to mpeg2. the resulting audio file that i want is ac3. as you may already know, tmpgenc doesnt recognise mp3 and ac3 I'v also read a guide that tells me how to keep the original ac3 audio from the avi by encoding only the video stream and adding the demuxed ac3 audio later when authoring the dvd.
My question is how do i get output ac3 audio when my original audio source is mp3, i could extract it as a wav using virtualdubmod and encode the wav to ac3 using tmpgenc sound player, couldnt i??but iv heard that would be kind of useless, is there any way at all?
and is the only role of ac3 that you can listen to audio with surround sound as well as its good compression rate, what is the point of it?
and also if i originally did have ac3 audio on my avi and its something like 256kbs is there anyway i can encode it to increase the audio bitrate and is there any point in increasing audio bitrate?
and one last question what is all this channel business? i dont understand this 2 channels and 5 channels and 8 channels
sorry for all the question but any help would be much appreciated
mubs

[Soopafresh]

If your source file is AVI with a MP3 audio, it is quite easy to make an ac3 or mp2 sound file. Unfortunately, encoding to a higher bitrate won't do any good, but you can filter and eq the audio to make your ears believe it sounds better.

Channels - individual sounds get moved to their own speaker to envelope you with a "theatre sound" -- "That guy on the right side of the movie screen is coming out of the right front speaker!"
See here for diagrams of a 5.1 setup. http://www.pantherproducts.co.uk/Articles/Audio/surround_sound.shtml

[mub6]

why cant i just encode it to a higher bitrate wont it just increase the audio quality, and if i do encode mp3 to ac3 wont that just not make it better, i heard that each time you encode something the quality of the file decreases, and what exactly does ac3 do? whats so good about it. can i only get surround sound with ac3. why is it better than mp2 and how do filter and eq the audio. also is there a way to increase the number of channels.

[mats.hogberg]

AC3 is the most efficient (audio quality vs file size) DVD specifications audio format.
Of course, the higher the AC3 bitrate you use, the closer to the source audio you'll get. But there is a point where you'll hear no difference. For stereo AC3, 256 kbps should be quite enough. I'm sure some audiophile will rise to the bait, but since your source is MP3 anyway (where all the best is already gone from ther audio anyway) I don't think you'll be disappointed.

/Mats

[mub6]

thanx for the reply so whats the difference between stereo and the other format, also does that mean that if the source audio is mp3 then encoding it to higher bitrate will make no change, also if the source audio is ac3 then what bitrate do u recommend i encode to or is there no point and, one more question, can i get surround sound only in ac3 or is it available with all formats as long as the correct number of channels are there in the source, and is there a way to increase the number of channels
thanx in advance

[yoda313]

I believe there is multichannel mpeg audio available but the support for it would be dramitically less than ac3. AC3 is the standard for DVD and supports 5.1. BUT if your mp3 doesn't have 5.1 you would have to artificialy create it from a stereo file. You'd be better off using a surround mode on your amplifier and it would save you a lot of time fooling around with it.

source audio is mp3 then encoding it to higher bitrate will make no change,

Generally speaking you can't improve on the original sound. Simply increasing the bitrate won't make it sound better. Now you can add filters to change pitch, tone, echos, and that sort of stuff but you can't make it sound richer like the original source without going back and using the original source in the first place.

[mub6]

thanx for the reply but if increasing the bitrate has no effect on quality, what exactly does it do, also what do you mean when you say ac3 supports 5.1, cant any audio format that has 5.1 channels be played with surround sound and how can you artificially create 5.1 from a stereo

[spanky123]

what do you mean when you say ac3 supports 5.1, cant any audio format that has 5.1 channels be played with surround sound

No. AC3 however does support real 5.1 and is also a dvd-audio format

The only dvd audio formats I know of are mp2, ac3 and pcm (which is just wav iirc), and of those, only AC3 is used with 5.1, although according to:
http://www.dvddemystified.com/dvdfaq.html#3.6.2
mpeg-2 audio and pcm both support 5.1, but they're never used in dvd afaik

how can you artificially create 5.1 from a stereo

There's no point. It's not gonna be proper 5.1. Your speakers will kindof just be cloning eachother, so you may aswell just leave it as stereo. All speakers should still work. Mine do anyways

thanx for the reply but if increasing the bitrate has no effect on quality, what exactly does it do

Makes the file bigger. You can't make something from nothing. It's only ever gonna be as good as the original at best*

*With the exception of some poor quality audio files that may be improved when run through some filters to remove background noise and crackling etc.

[yoda313]

The only dvd audio formats I know of are mp2, ac3 and pcm (which is just wav iirc), and of those, only AC3 is used with 5.1, although according to:
http://www.dvddemystified.com/dvdfaq.html#3.6.2
mpeg-2 audio and pcm both support 5.1, but they're never used in dvd afaik

Well not to confuse the original poster any more BUT you forgot to mention DTS surround sound.

[mub6]

what do you mean when you say that 'ac3 supports real 5.1' does that mean that ac3 is the only format that will play surround sound with each channel being assigned to a specific speaker; whereas other formats with 5.1 wil only play the same audio from each of the speakers???

you may aswell just leave it as stereo

what does that mean??? i dont understand the difference between stereo and mono and all of the other formats
Please can someone help me
Thanx in advance

Mubz

[mats.hogberg]

If your source audio is MP3, it's with 99.9999% certainty stereo (2 channels, left & right) so 2 channels is what you can get, regardless of what codec you choose to encode to.
If your source is already AC3, just extract it as is, encode video only, then use original AC3 + new mpg when authoring the DVD.
AC3 isn't the only 5.1 format - DTS can also be 5.1 IIRC. (if we're talking DVD audio)

/Mats

[mub6]

so does stereo mean that the audio has 2 channels, so what are the other terms and what do they mean???

Also if the mp3 source has 2 channels does that mean that it will still have the same two channels after converting it to ac3 or mp2 or any other format???

AC3 however does support real 5.1

what is meant by this statement does it mean that with AC3, each channel will be played from its own individual speaker whereas any other format would just play the same sound from all of the speakers

[mats.hogberg]

Mono=1 channel, one speaker (or the same sound out of all speakers if you have >1)
Stereo=2 channels, 2 speakers with different sound.
4.1, 5.1, 6.1 ... 4/5/6 speakers with different audio, + one bass speaker (which in its nature isn't directional)

/Mats

[mub6]

thanx for the reply
i was just wondering if my 2 channel mp3 source will still have two channels after i convert it into ac3?

also, when extracting the audio as a wav from the original mp3 source, am i actually encoding the original mp3 audio into a separate wav file because after that im converting the wav file into ac3 using tmpgenc sound player. this would mean im encoding the same source twice to get it to ac3 format. would this reduce the quality because each time you encode a file you lose some quality dont you, if i am encoding twice then would it be better for me to just demux the source mp3 audio and convert it to ac3 using besweet.

also if it isnt worth encoding the output ac3 file to a higher bitrate because i have a stereo source then in what circumstance do you recommend i do encode it to a higher bitrate
hope you can help me
thanx in advance
MubZ

[Coolpplse]

The only dvd audio formats I know of are mp2, ac3 and pcm (which is just wav iirc), and of those, only AC3 is used with 5.1, although according to:
http://www.dvddemystified.com/dvdfaq.html#3.6.2
mpeg-2 audio and pcm both support 5.1, but they're never used in dvd afaik

Well not to confuse the original poster any more BUT you forgot to mention DTS surround sound.

You are all wrong, These are the audio formats avaliable when the DVD is authored as DVD-Video

True DVD-Audio is MLP which can go from 16Bit/48Khz, 24Bit/96Khz, or 24Bit/192Khz
and 2.0 - 5.1

and DVD-Audio requires a DVD-Audio player

Now Retail DVD-Audio discs include a DVD-Video layer for existing DVD-Video Players which would then have the audio tracks in the video portion of their disc as AC3, DTS, LPCM, (MP2, no one uses this in a DVD-Audio really, but its just that you can )

[mub6]

yes i think thats what yoda 313 probably meant that the only 'dvd-video' audio formats he/she knows of are...
i dont really care about dvd-audio at the moment. Do you think you can help me in anyway

[mats.hogberg]

thanx for the reply
i was just wondering if my 2 channel mp3 source will still have two channels after i convert it into ac3?

Yes.

also, when extracting the audio as a wav from the original mp3 source, am i actually encoding the original mp3 audio into a separate wav file because after that im converting the wav file into ac3 using tmpgenc sound player. this would mean im encoding the same source twice to get it to ac3 format.

No, you're decoding the MP3 to wav (no quality loss at this stage) then reencoding the wav to AC3 (inevitably some loss). WAV is almost always an intemediate step when converting one audio format to another.

also if it isnt worth encoding the output ac3 file to a higher bitrate because i have a stereo source then in what circumstance do you recommend i do encode it to a higher bitrate

It's worth encoding at the bitrate where you can tell no difference if you go higher. It's your choice. There's no definitive answer. Just individual opinions. My opinion is: For stereo 256 kbps is usually quite enogh, for 5.1 448 kbps (but then encoding to 5.1 AC3 is rarely something you do).

/Mats

[mub6]

thank you so much
ok just one more question to go now (i think)
what software or application do you recommend i use for top quality when converting mp3/wav to ac3. im currently using tmpgenc sound player/besweet and im just wondering which gives best results or is there any other good quality audio encoder which encodes mp3/wav to ac3
Thanx in advance

[spanky123]

thank you so much
ok just one more question to go now (i think)
what software or application do you recommend i use for top quality when converting mp3/wav to ac3. im currently using tmpgenc sound player/besweet and im just wondering which gives best results or is there any other good quality audio encoder which encodes mp3/wav to ac3
Thanx in advance

I recommend Belight (which is pretty much just a GUI for Besweet)

It's very simple and very good (as it uses besweet) - judging by it's rating (9.5), others agree

[Coolpplse]

I would actually use TMPGEnc XPress to encode ac3 audio as since the program had to get a license from Dolby to sell its encoder and would have better quality

[mats.hogberg]

...and I'd use ffmpeggui, as it's free, simple and easy.

/Mats

[spanky123]

I recommend Belight (which is pretty much just a GUI for Besweet)

It's very simple and very good (as it uses besweet) - judging by it's rating (9.5), others agree

I would actually use TMPGEnc XPress to encode ac3 audio as since the program had to get a license from Dolby to sell its encoder and would have better quality

...and I'd use ffmpeggui, as it's free, simple and easy.

/Mats

There you go. Take your pick

My TMPGenc Xpress doesn't encode ac3 audio I don't think. Maybe I need to install the ac3 plugin

[mub6]

thanx so much for the reply guys, which one of those gives the best quality encode, i dont really care about ease of use or anything else but just quality
thanx in advance
MubZ

[spanky123]

I can only speak for BeSweet encoder (using BeLight GUI). This is all I use for encoding audio for my dvd's (except for when I'm lazy and just let TMPGenc or Procoder or CCE do it)

I can't tell the difference tbh.
However, I've been advised by others who know a lot more than me about this stuff, to use BeSweet.

Maybe there's an audio encoder shootout/comparison somewhere?

[mub6]

thanx for the reply
ye it does seem good this one but that ffmpeg gui got a slight higher rating than besweet although there are some complaints that it gives really low output ac3 volume but maybe they just need to set the bitrate slightly higher. i dont know
if loads of people who know what theyre talking about use belight then i guess its probably the one to use
any other opinions?

[mats.hogberg]

IIRC, BeSweet & ffmpeggui use the same engine for AC3 encoding, possibly different versions.

some complaints that it gives really low output ac3 volume but maybe they just need to set the bitrate slightly higher.

Bitrate has nothing to do with audio levels - just quality. Most who complain about low AC3 audio has the computer AC3 decoder set up wrong.

/Mats

[mub6]

oh ok thanx for that, iv tried em both out and i think ill use belight
thanx for all the help people
really aprecate it
MubZZ