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Question about rendering seperate audio & video for DVDA..


Is there a reason besides speed, quality etc., for rendering separate for DVDA?

In my experience, rendering a separate audio file takes longer than letting DVDA do it.. Almost twice as long..

No it doesn't. in fact, that is the faster way. If you include the audio in the MPEG2 file DVDA will re-encode the file and making the DVD/BluRay will take longer.

"[I]Is there a reason besides speed, quality etc., for rendering separate for DVDA?[/I]"

DVDs and Blu-rays can, and often do, contain multiple audio streams for different encoding formats, languages, etc. Taking that into account, it makes perfect sense for the authoring software to expect separate elementary streams.

For a single video and audio pair, how you do it probably doesn't rise to one of the world's major issues.

@Oldsmoke:

" No it doesn't. in fact, that is the faster way. "

Any Idea what I might be doing wrong?

When I render a 108 minute AC3 , from a captured VHS ( AVI with Vegas cap ), it takes 8:32.

When I take the rendered .mpg ( no .AC3 ) to DVDA, it only takes 4:33 to make a prepared DVD folder, including the audio encode..

It might make sense for an authoring program to prefer separate video and audio streams but it makes no sense to re-encode the audio when it is perfectly valid for the DVD or BD.

I suspect that in the case of DVDA, it is something to do with licencing the AC3 encoder. If you render to an AVCHD template in Vegas, you have the option of including the audio or not, but the audio is so-called AC3 Studio. What is AC3 Studio? My guess is that it is just normal AC3 without a flag that says it is AC3 Pro.

If you take the main feature video file (0000?.m2ts) from a BD authored by DVDA, you can author another BD with DVDA, but it won't re-encode the audio. Also, you can use say tsMuxer to multiplex a video stream and audio rendered as AC3 Pro, and DVDA will accept it without re-encoding the audio.

TMPGEnc Authoring works will make a BD from video straight from your camera or as produced by Vegas as a multiplexed file without re-encoding. Why can't DVDA?

So far as MPEG2 is concerned, the Main Concept encoder in Vegas creates an MP2 audio stream when you render video+audio.

DVDA doesn't like MP2 audio in DVDs, although DVDs with MP2 audio play fine on my players.


Why does DVDA take so long to re-encode? I don't know. The main thing is to find out what work flow makes DVDA happiest, and use that. Then you will be happy too.

" Why does DVDA take so long to re-encode? "

My point, is that it doesn't .. ( ..for me )

It takes over 8 minutes to render the .AC3 file in Vegas Pro 12, while re-encoding in DVDA takes only 4 and change..

OldSmoke, whose experience and advice I respect, said going with separate streams should be faster, so I'm wondering what I am missing..

I did some testing, and this is what I found.

I used a 6 minutes 30 seconds (6:30) long 1920x1080-50i AVCHD video recorded by a Sony camera. It had AC3 5.1 audio.

I smart rendered the video in Vegas 9c with and without the audio and also the audio alone. The render times were:
Video only 0:47
Video + audio (AC3 studio) 1:15
Audio only AC3 Pro 1:15
Audio only AC3 Studio 0:25

The AC3 pro audio took considerably longer to render. I would really like to know what the difference is between AC3 Studio and Pro.

I took the video only file and the AC3 Pro file and muxed them to a .m2ts file using tsMuxer.

I authored a menu based BD ISO file in DVD Architect 6 and noted the render and prepare times respectively for the following options

Source video file: 20:46, 2:34
Video + AC3 studio from Vegas: 20:52, 2:38
Muxed video + AC3 pro: 0:48, 2:40
video and AC3 pro as separate files: 1:27, 3:26

The render times for the first two are comparable and very long due to the re-rendering of the audio. I have a 4-core HT CPU (8 threads) but only one core was being used at a time (but not always the same one) at about 90%. Total CPU usage was about 12%. While the render times for AC3 Pro in Vegas are longer than for Studio, it is definitely preferable to do it there than in DVD Architect.

The render times of the second two show that it is preferable to have the audio and video pre-muxed. The separate files took 39 seconds longer, but tsMuxer took 33 to multiplex them.

The prepare times are comparable except for the separate files which was about 30% longer. There may therefore be some time advantage in pre-muxing audio and video before using in DVD Architect.

Stringer, I think I get a different result to you regarding audio rendering times in Vegas versus DVDA, but don't ask me why.

@Stringer

It is faster on my system too. I use Vegasaur to render the MPEG2 and AC3 in one go; put both into DVDA and there is no additional processing in DVDA other then preparing the disc image (BD) or disk folders (DVD).
But yes, the total rendering time for separate video and audio is longer then rendering an AV MPEG file. The problem is DVDA doesn't like the MPEG AV file and will re-render the audio; don't ask me why. Not only does then take longer in DVDA, I don't like to see my audio being re-processed.

Edit: I just tested a 40min. multicam project, AVCHD1280x70 60p with 3 Stereo audio tracks and rendering to AC3 took 1:49sec; video using MPEG2 1280x720 60p took 24min.

"I would really like to know what the difference is between AC3 Studio and Pro"
- The Dolby AC-3 'Pro' encoder offers more custom parameters such as; Service, Int./Ext. bItstream and pre-processing.

I suspected it might be something like that but my question should have been, "What is it about AC3 Studio the DVDA doesn't like?" As I said before, it is probably something to do with licencing.

The "studio" encoder is not registered with dolby and because of that I'm pretty sure it's only allowed to be used in a very narrow set of circumstances.

We went through the same set of questions with the now defunct Avid Liquid. You could create a surround sound disc with liquid but you could not export AC3 as a file or do any customizing or anything of that nature.

We were curious and actually wrote Avid and their response was "a licensing issue" and wouldn't go any further with the explanation

We then wrote Dolby for some answers and they were much more forthcoming. In a nutshell Dolby stated that they don't mind the existence and use of "home made" AC3 encoders, so long as those encoders were restricted to personal use and the Dolby name wasn't included on the finished product.

Given all of this, I would be inclined to believe the studio encoder contains some kind of flag stating this is not a real and/or registered dolby AC3 file, in order to avoid legal issues with dolby labs.


Let's make this clear though.... this is pure guess work and in no way fact.

"I use Vegasaur to render the MPEG2 and AC3 in one go". What part of Vegasaur do you use for this OS?

When I say in one go I mean I set it and go. I use the transcoder feature, set to render current project, select AC3, Mpgeg2 Blu Ray, and Mpeg2 DVD templates and let it render. I can use the same AC3 file for the BD and the DVD. Vegas will still render 3 times but it is still better then doing each separate.

> "DVDA doesn't like MP2 audio in DVDs, although DVDs with MP2 audio play fine on my players."

Actually DVD Architect is just trying to be compliant to the NTSC DVD specification. MPEG2 audio is not allowed on NTSC DVD's but it is allowed on PAL DVD's. That means that while most NTSC players will play it, they don't have to in order to be DVD complaint so you might find a player that doesn't include the MPEG2 audio decoder and for this reason DVD Architect doesn't allow it's use so that it's discs are always NTSC compliant. NTSC DVD's should only have PCM audio or AC3 audio.

~jr