Calling all xvid encoders, what audio compression do you prefer

[G)-(OST]

Hey, I have just changed the way I am encoding DVD's, I still use xvid codec, but I now encode to a file size 700mb or 2 x 700mb for movies that are longer than 1h 30m, (I keep the original AC3 audio for the 1400mb encodes, because there is plenty of room for the video bitrate), so now I have to recompress the audio to actualy be able get a descent bitrate for the video, AFIK most movies are encoded in AC3 CBR 448kbps, so what would you suggest for the following:

AC3 with less bitrate or mp3?
The lowest bitrate that you would suggest with each of these?
VBR or CBR?

or do you suggest a different alternative, I am not sure about the audio side of things, googling has came up with mixed results, I am sure I will get mixed results here to, but I thought I would ask anyways, thankyou

[T-Fish]

for older movies (that were only stereo or mono anyway) i use CBR mp3 @128kbps.
newer movies in general get 128-196 depending on the length and the movie
itself (i.e. what kind of movie).
thats for 700mb rips of course, otherwise i just keep the ac3 track as you said yourself.

[lordsmurf]

Downconvert to stereo 192kbps. Slight compression, but more transparent than 96-160kbps.

[jagabo]

I use Lame at 192 kbps CBR minimum. But I don't make 700 MB Xvid files.

[G)-(OST]

Hey, whats the go with the low audio volume after recompressing to AC3, I thought I would do what LSmurf said, but found that the volume had been turned down, I used FFMpegGUI for the re-encode, this is the first time I have ever encoded audio, so I don't know which way to go about it or which tools to use, is re-encoding the audio going to cause sync issues? I have found that alot of the tools for audio encoding have not been updated for along time, years even, are they out dated & past there use by date or are they still up to scratch with todays technology, e.g. ffmpegGUI, BeLight etc

[jagabo]

AC3 is typically 20 dB below MP2.

[chh]

When I convert DVB-T, or DVB-S, captures from MPEG-2 to Xvid, preserving Dolby Prologic II surround information, is my criteria for choosing the format of the audio-conversion.
Source audio from af DVB-T or DVB-S capture is normally MP2, two-channel, at 256Kbps, samplefreq 48KHz. (Have found one exception: TCM Nordic broadcasts audio in MP2, one-channel, at 96Kbps. Their video resolution is strange too: 544 pixels by 576 lines).

If the case is a programme shorter than approx. 70 minutes, I would go for 1x700MB and keep the original MP2 audio. If the programme is longer than 95 minutes, I would go for 2x700MB and keep the original MP2. (If it is really good, I would not convert it to Xvid, but author the Mpeg2 streams to a DVD).

If the chance of good surround information is less good, and the programme length is in the 90-105 minutes range, I would go for 1x700MB, MP3, two-channel at 128Kbps if possible. (128Kbps is as low as you can go, keeping the original 48KHz sample freq unchanged).
If surround is of no importance, I would use MP3, two-channel at 112Kbps an reduce the sample freq to 44.1KHz.
An old lengthy movie with mono-audio: I would try to fit it into 700MB, by converting the audio to AC3, one-channel at 64Kbps - 48KHz sample freq unchanged. 64Kbps audio, leaves you plenty of room for the videoinformation.

Same approach, if I need to convert a DVD, to take it to the summerhouse.

I have not yet fully plunged into AAC audio. At home I use a Philips DVP5990/12 - it won't play AAC audio. In my summerhouse I use a Pioneer DCS-575. It plays AAC, but only if coded with QuickTime/iTunes, and I don't need another bulk of software to bloat my PC.

[guns1inger]

I don't encode to arbitrary filesizes. If the source has 5.1 audio then I prefer to keep it. If the source has only stereo and is mostly spoken word then I use 128 kbps MP3, if it is music/effects etc then 192 kbps MP3.

[G)-(OST]

Wow! 2 months later, anyway, I like to back-up, up to 6 movies on a DVD, that Is why I encode to 700mb, or 1400mb if the movie is longer than the usual 1 1/2hrs, this way I know that the final disk will be around 98% full, give or take.

I am still struggling to get a decent audio encoder, most audio encoders here are really old, as I mentioned earlier on in this thread, & haven't been updated in years, does anyone have some suggestions? another question is, does anyone actually encode the audio with Vdub via lame mp3 or acm Dec, I personally don't like encoding the audio with Vdub, but maybe I am wrong in thinking that this is not good practice, what are your thoughts?

[jagabo]

I use VirtualDub and LAME ACM all the time.

[G)-(OST]

I'm glad to here it, well it looks like I will be using Vdub for audio encoding from now on, thanks jagabo

[jagabo]

If you need to bring the audio level up you can use VirtualDub's Audio -> Volume option.

[G)-(OST]

I have never used the audio part of Vdub, I always selected no audio thinking that vdub would mess the audio up, & especially I had no idea it had a volume option, I really much appreciate it.

[chh]

If Dolby Prologic II surround is not an issue, I also use Virtualdub with Lame ACM (or AC3 ACM for Dolby Digital). First-pass with audio disabled, and second-pass with audio.

If Dolby Prologic is important, I do the audio recoding separately with either Besweet or MeGui. Those two apps. gives you the possibility to flick a switch, which tells the codec to try to behave nicely towards surround.
Afterwards I mux video and audio with Virtualdubmod.

Regarding how well multichannel 5.1 audio recodes to 2-channel Dolby Prologic II: Go to the bottom of:
http://www.sr.se/sida/default.aspx?programid=2445
Download the 14MB DTS under "Surroundtest".
Unzip the one-wav-file-6channel-DTS, run it through MeGui with output set as MP2, 256Kbps, and the Prologic II tab set - I am amazed how well channelseparation is maintained by the innards of MeGui.

Now, why would I turn such a fish as a 5.1 DTS into a 2.0 MP2, 256Kbps? As mentioned above, MP2 at 256Kbps is the standard in DVB-T and DVB-S. I have asked Pioneer if one of the three aux audio inputs on my DCS-575 can split a 2-channel source (from my DVB-T/S combo) into 5.1 output, Prologic II style. They promise it works with USB or Disk media, but are in doubt when it comes to the line- and SPDIF inputs. So I am going to feed the beast with this recode and see what happens, and then tell Pioneer what their product is capable of.