MPEG Audio Vs LPCM Vs Dolby Digital (AC-3) - What is "b

[jmone]

Hi,
Any opinions on what is "best" or what the +'ve / -'ve of each type is when authoring a DVD from DV?
- MPEG Audio
- LPCM
- Dolby Digital (AC-3)

I live in Australia (a PAL Country) so MPEG Audio compatibility with DVD Players is not an issue like in the US. The reason for the Q is that with Advance=1 and AC-3=1 settings in Video Studio I get the choice but should I change from MPEG Audio which has always served me well?

Thanks
Nathan

[mats.hogberg]

LPCM is uncompressed, so has the highest quality, but takes about 10 times valuable disc space. AC3 is better than MP2 at the same bit rate, so should be your choice if you want compressed audio.
But there's nothing gained (just lost in the case of AC3) in going from MP2 to LPCM or AC3 if MP2 is what you got to begin with.

/Mats

[TeeeRex]

Hi,

It's not so much 'what is best' but what best suites the requirement.

MPEG Audio (MP2) is great for stereo, is compressed (at whatever quality you accept), does not take up much space on the disk (so you can gain a higher video bitrate for example) and is very compatible. You can actually get 5.1 in MPEG Audio but very few receivers/DVD players will reccognise this.

On the other hand - LPCM is uncompressed and therefore is of equal quality to the source, but it takes up a huge amount of disk space. Again compatibility is good.

AC3 or Dolby Digital 5.1 (or 2.0 for that matter) are also compressed formats but at higher bitrates than MPEG Audio. Obviously 5.1 needing more space than a DD 2.0 track (stereo).

So in summary - if you source is DV (from a stereo DV camcorder one assumes) and you want to maintain video quality over audio - then I would stick to good old MPEG Audio at standard bitrates !

I hope this helps...

[jmone]

Thanks guys, I'm coming from DV recorded as 16-BIT Stero on a JVC Camcorder. The audio is reported as "DV Audio -- PAL" in VS8, and I have to date been encoding as MPEG Audio as:
- Audio data rate: 384 kbps
- MPEG audio layer 2, 48 KHz, Stereo

I've had not probs and happy with the result but am I wasting space with 384kbps over the defaul 256kbps?

Thanks
Nathan

[TeeeRex]

Hi,

Yes you are 'wasting' space but the result of using a lower bitrate 'may or may not ' effect the quality. For example if the footage is of a birthday party (for example) then it's just dialogue and possibly some background music - you can get away with 128Kbits here (just..), but if you're recording say a music concert, then you will clearly need to go higher to get the clarity and definition.

Have a play - you've got the original PCM soundtrack on the DV tape anyway - so 'see how low you can go ...' !

[bugster]

but am I wasting space with 384kbps over the defaul 256kbps?

Thanks
Nathan

Yes but not that much in the context of a DVDr

[BJ_M]

Hi,

It's not so much 'what is best' but what best suites the requirement.

MPEG Audio (MP2) is great for stereo, is compressed (at whatever quality you accept), does not take up much space on the disk (so you can gain a higher video bitrate for example) and is very compatible. You can actually get 5.1 in MPEG Audio but very few receivers/DVD players will reccognise this.

On the other hand - LPCM is uncompressed and therefore is of equal quality to the source, but it takes up a huge amount of disk space. Again compatibility is good.

AC3 or Dolby Digital 5.1 (or 2.0 for that matter) are also compressed formats but at higher bitrates than MPEG Audio. Obviously 5.1 needing more space than a DD 2.0 track (stereo).

So in summary - if you source is DV (from a stereo DV camcorder one assumes) and you want to maintain video quality over audio - then I would stick to good old MPEG Audio at standard bitrates !

I hope this helps...

mpeg audio is not that compatable in N.America .... many players dont play 48khz mpeg audio .. dvd players dont even have to support it as its not in the dvd spec for ntsc ...

[lordsmurf]

Find the guide on my site (in AUTHORING area) and read it.

[DJRumpy]

MPEG-1 Layer 2 audio is fully supported as an optional audio track for NTSC players. The spec only says that the first audio track must be either AC3, or LPCM audio. I suspect most of the cheaper authoring software packages, which do not accept AC3 audio (LPCM, or MP2 audio only), just drop an AC3, or LPCM encoded MPEG as first play, and then put your input MPEG as the 2nd play (guessing here...I wonder if any of the authors of such software ever browse the forum? ).

I've examined the VOB streams produced by SpruceUp, and confirmed that a hidden 'Authored by SpruceUp' mpeg stream exists at the very beginning of the stream, although I've never looked at the audio. Technically, as long as that tiny clip contained AC3 or LPCM audio, you could use MP2 audio for your project, and not violate the dvd spec.

As to which is better, that depends on your idea of better. It looks like MP2 can actually achieve a higher compression ratio that AC3, but at a lower return in quality. AC3 also appears to be more robust when it comes to mastering errors. I've never had an AC3 encoded mpeg lose audio sync, while MP2 seems to do this more often.

[BJ_M]

MPEG-1 Layer 2 audio is fully supported as an optional audio track for NTSC players

its optional and dvd players don't have to support it --- and we have tested several that don't support it at all ..

you will find more support for mpeg audio in Europe as it WAS a DVD standard there for awhile ..

[DJRumpy]

I would suspect a problem with the encoded disk before I would suspect a player that didn't support it. Why would someone produce a dvd player that didn't fully support the DVD spec?

http://www.mpeg.org/MPEG/DVD/Book_B/Audio.html

Assuming it was common that someone produced an NTSC DVD Player that didn't support MP2 audio, we would also most likely see PAL players that didn't support AC3 audio, since AC3 audio for a PAL dvd player is optional, just as MP2 audio is optional for an NTSC player.

[thor300]

No no. The common with PAL DVDs made in Europe is that the audio track(s) are in AC3, so this is not really "optional" for PAL. MP2 is rare. I dont care what the site DJRumpy linked to says, PAL players support AC3 anyway. In a wild theory when confused by tech papers then maybe PCM would be most compatible, but in real life AC3 is just as good. Also, AC3 gives better sound at lower bitrates, bitrates we really need for the video as long as we dont have access to dual layer burners.

[BJ_M]

I would suspect a problem with the encoded disk before I would suspect a player that didn't support it. Why would someone produce a dvd player that didn't fully support the DVD spec?

http://www.mpeg.org/MPEG/DVD/Book_B/Audio.html

Assuming it was common that someone produced an NTSC DVD Player that didn't support MP2 audio, we would also most likely see PAL players that didn't support AC3 audio, since AC3 audio for a PAL dvd player is optional, just as MP2 audio is optional for an NTSC player.

You are thinking maybe of old specs for PAL ? see thor300 post -- he is correct, it USED to be the way you were thinking ..

I assure you we produce compliant dvd's and in testing -- we have found several players that do not play mpeg audio on a dvd ... as several players don't play svcd or other formats either -- optional playback formats are just that - options --- a dvd player does not have to support it ..

[DJRumpy]

Now your talking about a new format altogether (SVCD). No argument that there are DVD players that don't play SVCD. Different media, different audio frequencies, and in SVCD's case, different resolutions. We're talking about DVD players, not SVCD/CVD players. This entire argument is mute anyway, since I'm guessing none of us has purchased the full b-book spec.

As to the posted b-book specifications being out of date, I agree. There was one revision to the DVD-Video standard (version 1.1), posted sometime in 1998 (I think), but I can't find it online.

Just keep in mind that the spec is for a DVD Video Disc, and not for a DVD Player. I tried to find out what the DVD-Video logo requirements are from the Pioneer site, but they also require a purchase

That said, a DVD manufacturer would be insane to produce a PAL dvd player that did not support AC3, even though it was listed as optional in the spec (v1.0).

The simple answer is, use whichever you like. If your player doesn't play an MP2 disc ( for whatever reason ), then use AC3.

[DJRumpy]

Well I found the pricing to get the B-Book (latest version).

http://www.dvdforum.org

$10,000.00 US. I think I'll just use whatever works.

[BJ_M]

we have purchased the full specifications -- not that that changes anything .

i have the full info for the use of the logo as well ...

[DJRumpy]

I mistyped that. The pricing is for the DVD-Video logo, and not the B-Book.

The B-book costs $5000.00. The Logo costs 10,000

Considering the fact that the book comes with a non-disclosure agreement, you'll forgive me remaining a skeptic.

[BJ_M]

the logo - for SOME applications , costs 10grand ... for others - not ..

its a sliding scale ..

i think our company is listed somewhere on the one of the lic websites as one of the founding members (look up ube iwerks (as in disney) and see if that rings any bells, if that doesnt - try imax ridefilm or simex ) -- if that will make you feel any better (hehehe) ... i havn't disclosed anything that is not public domain -- and i believe the public knows everything there is to know anyway pretty well .. maybe more in some cases ..

[mats.hogberg]

You work for iwercs? I just loved the theatre at our amusement park with those moving chairs - is it the same iwercs? Sadly, it's replaced by a 3D cinema now - Not at all as cool...

/Mats

[BJ_M]

iwerks - yes ... imax ridefilm, iwerks , turboride, simex, simex digital studios ....... all one in the same ..

tis me

[mats.hogberg]

Oooooh! Those roller coaster rides - "Elvira" et al - I just love 'em! Hopefullt they (the amusement park) understands what a big mistake it was to pull out those hydraulic chairs and replace Elvira with boring kids 3D stuff and even more boring "A beautiful world under the sea" that I've seen 100s of times before with Costeau.

/Mats

[sdsumike619]

Ok, so I've encoded my .mpg files with MP2 audio - Of course that was before reading this thread....Is there a way that I can convert the MP2 audio of my .mpg files to AC3? without having to re-encode the video? Please say yes

MiKe

[sdsumike619]

ok, so I discovered ffmpeggui and it works! Now the next question, Now I have the original .mpg file (video and mp2 audio) and the AC3 file that ffmepggui created,,, how do I dump the mp2 audio from the mpg and switch it with the AC3?

[mats.hogberg]

You demux it (U can use TMPGEnc for this), then keep the m2v and author to DVD with m2v as video and your ac3 as audio.

/Mats