Do I Need to extract audio?

[frappawotsit]

Hi,

I keep reading on this forum of the best way to keep video quality high is to demux the audio, re-encode it in AC-3 to allow a higher bitrate to be used for the video.

However,

If my DVD's are only ever a maximum of 60mins, do i still need to go through the above process? Will i achieve any visible quality difference, or can i leave the audio muxed in with the video and encode at a high enough rate that i won't see any difference?

I'm prepared to go through the process if necessary, but i don't want to go through the effort if i won't actually achieve any gain?

thanks.

-Stu

[AlanHK]

Where does your original video and audio come from?

Encoding audio to AC3 is pretty fast.
On my PC, about 1 minute/20 minutes of sound.
Video however takes at least 2 minutes/minute of video; i.e encoding audio is about 40 times as fast as video (roughly). So saving time encoding audio is minuscule compared to the total.

However, one hour of WAVE (uncompressed) audio is about 500 MB.
High-quality AC3 is about 100 MB. The saving is pretty large and if used for video should make a noticeable difference.

But anyway, easy enough to make a few test files and see for yourself if it matters.

[frappawotsit]

Where does your original video and audio come from?

Encoding audio to AC3 is pretty fast.
On my PC, about 1 minute/20 minutes of sound.
Video however takes at least 2 minutes/minute of video; i.e encoding audio is about 40 times as fast as video (roughly). So saving time encoding audio is minuscule compared to the total.

However, one hour of WAVE (uncompressed) audio is about 500 MB.
High-quality AC3 is about 100 MB. The saving is pretty large and if used for video should make a noticeable difference.

But anyway, easy enough to make a few test files and see for yourself if it matters.

My source file comes straight from DV Camcorder. Import from cam using windv, then edit in premier elements 3. When i open the .avi files in adobe prem, the audio is already matched to the video. I tinker about with it all, then render it to an mpeg which contains both. As to which type of audio, i'm assumig .wav?

1) So how do i go about seperating the audio/video signals
2) How do i convert from .wav to .ac3
3) How do i get the audio back to the video and perfectly synchronised?

Can i do as current, ie do all my editing etc of both video and audio in adobe prem, then when i'm completely finished, instead of rendering to mpeg2, is that where i seperate the audio?

If done at this stage, would that mean that when i put the two files back together i don't need to worry about synching, because it should already be synched? Or because of the compression, does it need to be re-aligned with the video?

I guess that's the main part that scares me, is just how difficult it sounds to get the audio perfectly in sync with the video??????

[AlanHK]

I don't use Premiere. but I'd be amazed if it couldn't handle all the common audio formats by itself.

I suggest you ask a new question, with Premeire in the title and you'll get some more applicable hints.