I have encoded my assets with compressor, video is 2 pass vbr av:6.8mbps peak 8 mbps and audio isc ac3 192kps with Dialog Norm at -31dB
For some reason I can still hear some levels variations (very suddle this time) that are not in the mix.
I am thinking of using PCM uncompressed audio this time but I would like to be sure that the final dics will play without issue.
They should since with video peaking at 8mbps and PCM audio at 1.54mbps the total is under 10mbps.
Would it be safe to go the PCM audio route.
Thaks in advance,
JJ
Re: AC3 or PCM Audio by Alexander Kallas on Jun 12, 2009 at 5:05:46 am
[Jean-Jacques Briquet]"I have encoded my assets with compressor, video is 2 pass vbr av:6.8mbps peak 8 mbps and audio isc ac3 192kps with Dialog Norm at -31dB "
The -31db setting will copy the set volume of the source audio, did you check in FCP that you were
happy with that?
[Jean-Jacques Briquet]"I am thinking of using PCM uncompressed audio this time but I would like to be sure that the final dics will play without issue.
They should since with video peaking at 8mbps and PCM audio at 1.54mbps the total is under 10mbps.
Would it be safe to go the PCM audio route. "
Maybe depending on the total file-size, but the standard for DVD audio is ac3, and no, this will not sound different, unless you have the hearing of my German Shepherd.
The total is the critical disc space (in Gb and Mb) and not data rate ( that's another story)
Re: AC3 or PCM Audio by Alex Asp on Jun 12, 2009 at 11:34:15 am
Actually, PCM _IS_ the standard for DVD, it's just Dolby Digital that became ubiquitous because it has lover bitrate and smaller file sizes. It is definitely has to do with bit-budget rather than with file size because you always have to make sure your material will fit on a given disc.
Lastly, it is definitely _NOT_ safe to use PCM audio unless your discs are replicated. Given the crappy under-$30 DVD-players, and lack of horse power of laptop computers your playback will suffer if your discs are burnt on a cheap media.
I double, triple, quadruple checked. this is not the first time this happened to me. The audio mix is really compressed like an audio CD. Sounds great in FCP and there are levels variation in the ac3 encode. If I disable the dialog normalization in the DVD player the audio is the same as fcp, unfortunately the default in people's dvd player is on for dialog norm.
Disc size is not an issue, we are going to dvd9
Re: AC3 or PCM Audio by Alex Asp on Jun 12, 2009 at 6:32:51 pm
If the project is going to be replicated you should be fine as long as combined bitrate for all streams does not exceed 9.8 Mbps. If you have used Compressor for video encodes you should check that the bitrate does not spike over 8.3 Mbps, or even replicated disc will stutter in some cheapo players. And to get rid of the level fluctuations in AC-3 file it is not enough to set the dialnorm to -31 but in the Pre-Processing tab of Dolby encoder all of these items need to be unchecked: Digital De-emphasis, Low-pass filter and DC filter.
Re: AC3 or PCM Audio by Noah Kadner on Jun 12, 2009 at 7:09:09 pm
I will unequivocally say do not ever use PCM replication or not- your discs will skip on certain players. Every Hollywood DVD made today is encoded in AC3. If it doesn't sound right that's a mixing issue not an encoding issue.
Thank you Alex, I will try with Low-pass filter and DC filter unchecked and report back. Btw, how do you check the bitrate spikes, is there a specific software on Mac that can do that.
Re: AC3 or PCM Audio by Alex Asp on Jun 12, 2009 at 8:42:12 pm
There is no Mac software for analyzing MPEG streams that I am aware of, but if you are running an Intel Mac there is plenty of free software you can find. Even a simple tool like Bitrate Viewer will be good enough, and it will run under Windows with Parallels, BootCamp or VMWare.
It is imperative to un-check all 3 options in Pre-processing tab and it will take care of your problem with level fluctuations. Leaving those options on is a common mistake that affects quite a lot of DVD authors. Of course those who know those little dirty secrets, or have read Dolby papers can make a nice living out of consultancy :-)
