AC-3 or LPCM

[slacker]

Other than the compression factor, I DON'T QUITE understand the value of AC-3. Maybe there isn't any. I know the dynamic range issues are a pain in the ars. If I don't need the compression, why do I want AC-3? I can author an hour of video from quality DV-AVI source using the Vegas installed MainConcept encoder @ 8mbps with LPCM or 9.2mpbs with AC-3. If my goal is supreme quality, what should I be contemplating here?

[DRP]

You shouldn't. If saving space is of no concern to you then by all means go with PCM. PCM is the ultimate quality. You cannot get better than PCM... but... it takes up a 5417-load of space and you might have to compromise the video quality to make it fit.

[GeorgeW]

bitrates approaching the max for dvd specs on home-made dvd's can cause problems in dvd players. Their playback could stutter (could depend on other variables like the quality of the discs, the burner and burn speed). If your dvd player handles it fine, then that's great. But if your dvd will be for a wider audience, then I would suggest lowering the overall bitrate to under 7.5mbps (video and audio tracks combined).

[slacker]

Thanks guys!

I 'm leaning toward 8mbps with PCM, primarily because the AC-3 dynamic range drives me NUTS and these particular videos are edited family videos spanning 25 years and I would like to archive as BEST as possible and store along with their DV tape counterparts.

[lenti_75]

8000 is NO problem for any dvd

9500 and higher is a problem.

if the space is no problem go as you said, 8000 and pcm.

[GeorgeW]

just to avoid confusion, are you saying 8mbps video plus pcm audio, or are you saying 8mbps will be the combined bitrate (video plus audio)?

[slacker]

GeorgeW. For 1 hour of DV video, DVDA is giving me

using PCM
08.000 video bitrate (Mbps)
10.080 overall maximum bitrate (Mbps)
09.748 overall bitrate (Mbps)
01.536 total audio bitrate (Mbps)

or

using AC-3
09.200 video bitrate (Mbps)
10.080 maximum overall bitrate (Mbps)
09.600 overall bitrate (Mbps)
00.192 total audio bitrate (Mbps)

[GeorgeW]

imho, 8mbps video plus additional pcm audio (1536kbps) will bring your total bitrate up to ~9536kbps -- within dvd specifications, but too high for home made dvd's (as I've seen many dvd players choke on such a high bitrate on home made dvd's).

If you must go with 8mbps video, then go with AC3 audio (224kbps should be fine) -- that will keep your total bitrate down to about 8224kbps (still a little too high for my taste, but better chances of smooth playback than 9536kbps).

Personally, I would lower my video bitrate to 7mbps, and use AC3 audio (for dvd's that I would be distributing to a wider audience where compatibility is a factor).

[slacker]

GeorgeW,

These particular dvds are all family videos spanning 25 years which will accompany their DV tape counterparts for archiving. The sets will be given to my three children, and ONLY to my three children. I want the best quality for them going into the next generation.

In thinking about compatibility, one of my assumptions here is that dvd players will be getting better, not worse, in the future. My Panny ES30VS using the default XP setting encodes the video @ 9.1 Mbps (average) and audio @ 256 Kbps (AC-3). And it looks great!

As for dvd players that choke at higher bitrates, personally I don't think they'll be around much longer relatively speaking.

Based on your inputs though...
Now I'm thinking 8 Mbps video and 448 Kbps (practical limits) AC-3 audio with dynamic range compression enabled. That may work okay.

[FulciLives]

If you want to use LPCM audio then be safe and use a video bitrate of 7500kbps

Trust me the difference between a CBR of 7500kbps and a CBR of 8000kbps are so small you would be super human to tell the difference.

For family videos I would do a CBR of 7500kbps with LPCM audio. That should get you about 60 minutes ... maybe a bit longer. Depends on your authoring overhead.

If you want 8000kbps video then use 448kbps 2.0 AC-3 but make sure you do it right!

There is an excellent guide on the doom9 forums about how to do AC-3 correctly. The best would be to normalize up to but not past 0.0db (without any dynamic range nonesense) then set the AC-3 to -31db and BTW the guide is a sticky in the AUDIO ENCODING forum.

The only "hitch" with AC-3 is that you need some expensive software to do it correctly.

- John "FulciLives" Coleman

[slacker]

Thanks FulciLives.

I will peruse the Doom9 thread on AC-3. It looks ominous!

In Vegas, below are the instrx for approximating PCM sound levels when replacing PCM with AC-3.

• The AC-3 encoder can be configured to perform dynamic range compression.
  
  When rendering your AC-3 files, change the following settings in the rendering template:
  
  In the Render As dialog, choose Dolby Digital AC-3 from the Save as Type drop-down list.
  
  Click the Custom button. The Custom Template dialog is displayed.
  
  Select the Preprocessing tab.
  
  From the Line mode profile drop-down list, choose None.
  
  From the RF mode profile drop-down list, choose None.
  
  Click OK to close the Custom Template dialog.
  
  Click Save to render your file.
  

If you want 8000kbps video then use 448kbps 2.0 AC-3 but make sure you do it right!

1st pass speed reading, the Doom9 thread comments that 448kbps only makes sense with 5.1 and 192kbps for 2.0 stereo. However, I would go with your 448kbps recommendation only because I think bigger is better when it comes to digital info.

The best would be to normalize up to but not past 0.0db (without any dynamic range nonesense) then set the AC-3 to -31db...

Vegas defaults to -0.1db rather than 0.0 db and -27db rather than -31db. All in all, pretty darn close to your recommendations. Not that the defaults are right, but evidentally Vegas developers are referencing the same standards you are.

The only "hitch" with AC-3 is that you need some expensive software to do it correctly.

Vegas seems to have all the AC-3 audio "stuff" available. But I'm no expert for sure.

I think I'll go read the Doom9 thread now!

[FulciLives]

VEGAS is fine for AC-3 but it is expensive so I never assume someone has such a program LOL

Nothing wrong with normalizing just less than 0.0db as you say VEGAS does but the reason for the -31db setting is that ... according to what I have read ... this is the setting that will retain the original volume of the PCM WAV when converting to AC-3 if you do NOT intend to fool around with dynamic range compression.

The doom9 thread should help you to understand what I am talking about.

- John "FulciLives" Coleman

P.S.
Usually 256kbps is more-than-good enough for 2.0 AC-3 with 192kbps being on the "low" end for 2.0 AC-3 but since you are worried about quality ... no reason not to go with 448kbps 2.0 AC-3 unless you really need to "push" the minutes on the DVD (i.e., want to go well beyond the 1 hour mark).

[Wile_E]

I am still trying to figure out TMPGEnc AC-3 Encoder. It has an option to enable "AC3 Compression". I know that it is just a flag, and doesn't touch the dynamic range. It just tells the DVD player to apply dynamic range compression on playback. But the thing is, how much compression is it telling the dvd player to apply? My player has option to turn the compression on/off, so I know the flag does work. Files encoded without the flag, don't do anything when I enable the compression on my player.

[DRP]

I don't understand the problem with AC-3 audio at all. I use the TMPGEnc AC-3 plug-in through DVD-lab PRO and nothing could be more straight forward and easy. I just apply a radio ReplyGain to the WAV I want to convert using WaveGain from RareWares and then compress it with DVD-lab PRO/AC-3 Plug-in. The volume always comes out at the same level as any other audio like PCM/MP2 etc.

I've heard ridiculously soft audio on original DVDs with 5.1 AC-3 before, so I can only imagine this is what's being referred to, but if AC-3 2.0 is all that you can encode, this isn't a problem. I don't get it.

[Noahtuck]

I am still trying to figure out TMPGEnc AC-3 Encoder. It has an option to enable "AC3 Compression".

Do you mean through TDA or in TMPGEnc or just in general ? because i did not know you could use the ac3 encoder in TMPGEnc

I use the TMPGEnc AC-3 plug-in through DVD-lab PRO and nothing could be more straight forward and easy.

See, that's weird, because i also use the TDA ac3 plugin encoder to encode small files to ac3 in DVD-lab PRO with no problem but i have never been able to get it to work in TDA ??
I have the TSUNAMI-MPEG DVD EasyPack and it works in there woth all 3 programs, but never through TDA ??
I only use it for menu's as i usually do audio through Adobe Audition and/or Vegas.

[DRP]

I don't have TDA. Honestly, if you have DVD-lab PRO why on earth would you ever consider using another authoring program at all, especially one as numpty and restrictive as TDA?

[Noahtuck]

I don't have TDA. Honestly, if you have DVD-lab PRO why on earth would you ever consider using another authoring program at all, especially one as numpty and restrictive as TDA?

Because TDA is a great and simple program for people to start with and learn without it being overwhelming 8)

And i will always endorse as they make some GREAT programs!!
Espc. TMPGEnc

[whitejremiah]

yea, TDA is a little less scary to use for the first few times...agreed they DO make great programs, heck i used to use TDA myself until i felt comfortable enough to give the free trial of DVD-lab Pro a try.........and although it is definately a more powerful program, i remember looking at it the first time and i was just FLOORED...didn't even know where to begin on it......if your just goin for a quick conversion with nothing too fancy, TDA works for that...very well actually.

[DRP]

I started with DVD-lab PRO. It was the first authoring program I ever tried because I wanted to create DVD-SVCD straight away and I quickly established it was just about the only program that would allow me to do it without drama. Afterwards I read about TDA and gave it a whirl just to see what all the talk was about. It's a joke compared to DLP. It lasted about 15 minutes on my computer before getting the heave-ho. Needless to say I never authored a single thing with it since it wanted to prevent me doing just about anything that wasn't 100% within all the standards.

[guns1inger]

it wanted to prevent me doing just about anything that wasn't 100% within all the standards

Which isn't such a bad thing. Yes, by comparison TDA is restrictive after using DLP. But not everyone needs that power. I use DLP, and keep strict compliance turned on, so it is just as restrictive as TDA in so far as adherence to standards goes. I suggest you start to learn how to work within the standards as well. It makes for better compatability in the long run.

[Noahtuck]

since it wanted to prevent me doing just about anything that wasn't 100% within all the standards.

That alone is funny
Because TDA actually won't let you do things in the dvd spec's that are not 100% and DVD-lab PRO WILL allow you to do things on dvd that are not 100% in the dvd spec's 8) and do you realise how may people have a hard time just doing thing's within the dvd spec's ?? let alone outside of them

I wanted to create DVD-SVCD straight away and I quickly established it was just about the only program that would allow me to do it without drama.

SVCD doe not fall into the standard dvd spec's 8) so it is not 100% compatible....

And if you are dealing with the masses out there... you can't afford to NOT be 100% compliant within the dvd spec's

Anyways, i agree, DVD-lab PRO does blow away TDA.... but in it's own right, TDA is a rockin' program!!!! espc. for starting out

And what he said 8)
guns1inger

And i have yet to find a program as versatile and as good as TMPGEnc for encoding video!!!
So pegasys programs are on top just for that one alone 8)

[DRP]

Don't get me wrong, I agree that TMPGEnc Plus 2.5 is great. It's my No. 1 encoder no question. But it is of a very old generation now. It was written back when Pegasus *were* worth your adulation. Unfortunately TDA is part of the *new* commercial Pegasus which also created TMPGEnc 3.0 XPress to replace TMPGEnc 2.5 Plus. The *new* Pegasus is no where near as good as the *old* Pegasus.

[slacker]

DRP and all...

So here's the thing...

After reading the articles on the Doom9 site as suggested, it seems to me that MOST people that are encoding AC-3 are just crossing their fingers that everything is going to come out okay.

Minimally, in order use dynamic compression properly I believe you need to know what the clip's LAeq and RMS levels are. If you don't have that, you're settings will be way off. Just setting your normalization at -31db or -27db is not the answer.

Therefore, it seems to me that the ONLY way to encode AC-3 properly is to invest in a product like Sound Forge 8.0 to give you access to those RMS numbers. Although Vegas 6.0 has some wonderful audio tools, even IT does NOT give you your LAeq or RMS levels.

One of my frustrations revolves around the line mode profile which uses the five dynamic compression settings. Which one do you use? And in Vegas, they tell you to select "NONE" for line mode to most closely match PCM levels. There isn't a "NONE" setting the the DD specs!!! Too confusing.

To do it right or not at all, I guess I buy Sound Forge or stick with LPCM.

[Wile_E]

I am still trying to figure out TMPGEnc AC-3 Encoder. It has an option to enable "AC3 Compression".

Do you mean through TDA or in TMPGEnc or just in general ? because i did not know you could use the ac3 encoder in TMPGEnc

I'm using the AC-3 plugin seperately, to convert wav to ac3. Just open up TMPGEnc sound player, and click Encode button. Then choose Dolby Plugin. Then press the Settings button. It has an option for "compression". This sets a flag in the file, for the dvd player to read, telling it how much dynamic range to compress. The problem is, no one knows how much is applied. Nothing in the documents about this option. Is it applying -31db to the file? I don't know, because there is no way to check. Only DVD players and software players know what to do with this flag, and use it to adjust the volume. Opening the file up in an audio program reveals the original audio. They don't know what to do with the flag.

[slacker]

After reading the Doom9 article, I would think that GENERALLY to "turn up" the volume on the video (if sound volumes are low after encoding) you would want to use the "Speech" profile.

But in Vegas they instruct you to actually choose "None" for Line mode, which is where you would select "Speech" or "Film Light", etc. Anyone know the whys behind Vegas' instruction? It seems backward to me which means I am totally confused.

[FulciLives]

After reading the Doom9 article, I would think that GENERALLY to "turn up" the volume on the video (if sound volumes are low after encoding) you would want to use the "Speech" profile.

But in Vegas they instruct you to actually choose "None" for Line mode, which is where you would select "Speech" or "Film Light", etc. Anyone know the whys behind Vegas' instruction? It seems backward to me which means I am totally confused.

My understanding ... partly based on the doom9 article as well as other various threads I have seen here or there ... is that you select NONE for compression and use Dialog Normalization of -31db ... doing so will give you a volume level identical to the original LPCM WAV file ... but you don't get any dynamic range "ability" this way. If you want to do that then you need SoundForge and then follow the doom9 guide.

- John "FulciLives" Coleman

[DRP]

I think you might be better off asking these questions in the Audio section now. Personally though I think you're trying to make something which is really very simple into something very complicated for no apparent reason. The way I do it reveals no audible clipping and the volume is always the same regardless of source levels.

[Noahtuck]

I'm using the AC-3 plugin seperately, to convert wav to ac3. Just open up TMPGEnc sound player, and click Encode button.

Yep, i have done this a few times, but my point was when playing back vid's through TMPGEnc DVD Author you still can't hear anything and it does not show up as being installed, say's it can not find it and it is not installed, even though it works great through DVD lab PRO, TMPGEnc sound player, & the TSUNAMI-MPEG DVD EasyPack.
And just because you said something about TMPGEnc that maybe the latest version could use it, i am running V2.521.58.169 and the latest vresion on their site is V2.524.63.181, that is what it sates on the download, yet when i DL it, it say's it is V3.524.63.181
Oh well, update time i guess and check the change log to see what the diff. is because i have never had a problem with the version i am running...

[slacker]

DRP,

Using Vegas, I encoded 1 track with LPCM, 5 separate tracks with AC-3 using various settings for Dialog Normalization and Line Mode as suggested and discussed in various threads and on the Vegas web site. In all 5 cases, the audio absolutely and distinctly does NOT resemble the LPCM counterpart. So either you are hard of hearing, have extremely low expectations regarding source replication, or you are a magician who must share his secrets. I hope you are THAT magician!

[slacker]

BTW FulciLives,

-27db (Vegas default) with compression disabled came close but still too SOFT. Tomorrow morning I will try -31db and see what happens per your recommendation.