variable or constant mp3 for audio? popular settings?

[AceRimmer667]

I am wondering what anyone can recommend to use for audio settings when converting to divx- I have heard some players may have trouble with variable mp3 bitrates, and i might be better off using constant. I thought constant audio bitrates might lessen the overall quality of the picture (if its a set size for the finished avi file) but im not sure how noticable this would be. If converting movies to a set size, should i stick to 128kbps or lower for audio, and will anything higher than 128 significantly lower the video quality if im converting to a set size for my finished video- what do you use for videos roughly around one compact disc in size at 700 mb? thanks for any info

[CWR03]

Whether you constant or variable bitrate for audio, the separate audio file will be the same size dependent on the bitrate you select.

As far as what bitrate you should use, it's purely a matter of your own perception. Use the lowest setting that doesn't cause a significant loss to you; no one else can make that determination.

what do you use for videos roughly around one compact disc in size at 700 mb?
Why are you still using 1 CD size? If you're so worried about video quality, go to a bigger file size.

[AceRimmer667]

thanks for the reply! I thought to use 700mb since some conversion sites recommend it as a good size for divx of around 60 to 90 mins whilst still maintaining a reasonable quality. when converting family videos from either vhs or dvd to give to relatives, cds recommended for burning given the 700mb size and cost of blanks nowadays. Some sites say i will save alot of space using variable bitrate mp3 instead of constant, i just wasnt sure if the amount would be significant or not to bother trying variable out.. and i heard many non pc divx players have trouble playing variable. Do you know if auto GK always uses mp3 when converting from disc, when "auto" audio type is selected?

[CWR03]

Variable bitrate may save some space, but most encoders, such as AutoGK, use average bitrate. In that instance, it makes no difference.

Do you know if auto GK always uses mp3 when converting from disc, when "auto" audio type is selected?
No, it uses whichever it can fit without sacrificing video quality. If you encode a 45 minute TV show episode at 640 x 368 and 700mb, it'll dump AC3 audio into it. The same encode at 350mb it would likely use MP3.

[AceRimmer667]

thanks for the reply. what settings would you personally use for mp3 if you were doing the same? would you go for variable or constant-you mention autoGK using average bitrate, is that the same as being constant, with the program choosing the kbps value itself?

[CWR03]

Perhaps you should read the documentation for AutoGK, as well as a few threads on audio encoding, and maybe the forum rules (http://forum.doom9.org/forum-rules.htm), especially #1.

[AceRimmer667]

ok thanks

[yetanotherid]

Don't worry about it AceRimmer667. It's a pity there's no equivalent forum rule #1 for replying.

ABR and VBR are both varying bitrates. The first method takes the chosen bitrate and tries to make it the average bitrate when encoding. The second method tries to vary the bitrate to produce a constant quality. So the second method gives less predictable file sizes. At least that's my understanding of it.

I looked through the forum documentation etc but couldn't find where it says which audio type CWR03 prefers. I've no idea why he suggested to look there.

Personally I use the ABR method, but I suspect it's more likely to cause sync problems in standalone players (hard to know as if I have sync problems they seem to more often be ABR, but then again I use ABR more).
Why limit yourself to a 700MB file though?? I don't understand why 350MB, 700MB etc are still standard sizes. Who burns to CDs any more? When I'm converting I usually take a guess but start at around at least 1GB. It's not very often you can squish a movie into a 700MB file and keep the resolution/quality up. In fact I prefer to keep the original audio and make the file size even larger if I need to. It's better quality and not needing to convert it makes the process quicker.

[AceRimmer667]

thanks for replying! i just wanted to hear other peoples preferences for particular audio rather than whats usually recommended in any rules, just incase anyone had a good reason not to follow them strictly (unless the rule im supposed to follow is 'dont ask obvious questions that you can find in any guides!'.. youre right about burning to cds, but then i guess if you convert to large sizes and start to approach sizes common for any movie on its own (ripped straight from a dvd with no xtras, 2 to 3 gig per movie), some may wonder if its really worth the wait of converting to divx at all. most players can run vob files straight from the hd too with the right software (if necessary). thanks everyone

[CWR03]

unless the rule im supposed to follow is 'dont ask obvious questions that you can find in any guides!'
Basically, yes. On top of that, the spirit of Rule 12 "Do not ask what's best" is to prevent pointless debates over something such as audio bitrate when that selection depends entirely on your use of the end file and whether you and not someone else is satisfied with the quality.

If I were to say that I use 128 kbps abr MP3 audio, invariably someone would come behind and tell me that I should only use constant bitrate. If abr suits my needs and sounds good enough for me and without audio synch issues with my playback methods, that's all that matters.

[AceRimmer667]

i cant ask for personal opinions or on what anyone uses for their own settings without any fighting! at least thatll mean a very active forum, can only be a good thing :) No mention of any method as the 'best' one-that should stop the arguments! in theory anyway :) lol. as youve said, what is truly the 'best' option aside from personal pref is also going to differ greatly depending on what is finally being used to play, eg some devices possibly only understanding constant bitrates, etc. a short summary of chosen personal settings with what they are converting to divx (and what they finally use to play) would give me a good idea on what i could go for, that was all i was after-probably asking too much there.. :-) lol. thanks for everyones info

[yetanotherid]

thanks for replying! i just wanted to hear other peoples preferences for particular audio rather than whats usually recommended in any rules, just incase anyone had a good reason not to follow them strictly

Naughty, naught, naughty!
Don't you realise asking what people prefer to do is in the same spirit of asking what's best?
LOL. If I was to tell you I prefer to use CBR (the actual bit rate isn't relevant to your question) then in the context of your question I'd explain why I do so. Someone else may come along and say they prefer ABR and explain why. I don't think that means we'd then have to debate who's right and who's wrong. My standalone player simply mightn't play ABR audio well. That's the sort of thing you were after isn't it? Just the benefit of other people's experience?

youre right about burning to cds, but then i guess if you convert to large sizes and start to approach sizes common for any movie on its own (ripped straight from a dvd with no xtras, 2 to 3 gig per movie), some may wonder if its really worth the wait of converting to divx at all. most players can run vob files straight from the hd too with the right software (if necessary).

At the risk of appearing to be arguing over what's best.... ;-)
I'd have thought most DVDs were around the 4GB mark, but regardless.... I think the DVDs I rip myself are usually between 1GB and 1.5GB at full resolution. Trying to squish one down to 700MB sacrifices too much quality for me, although it does depend on the source material.
If for some reason though I was aiming for 700MB I'd probably go for 128k CBR audio and I'd enable AutoGK's ESS compatibility setting (actually I leave that enabled all the time anyway). That way you'd end up with as good a quality video as possible while still having an AVI you should be able to play on anything. I'd avoid dropping the audio quality any further than that myself.
I use XviD though, not DivX, so can't tell you if that would make a difference. Probably not.

[AceRimmer667]

i usually convert to watch for when on the move via laptop, so sound and video does not have to be amazing, just watchable, as ill probably delete after use anyway. ive used xvid, although i dont see the slightly better video quality it gives over divx for identical file sizes, so i probably need glasses! one main problem i have is deciding on a set resolution. i wonder if there a recommended range to stick to, as 'auto' can give differing screen sizes for the end result, even with movies of equal length and similar content. Ill assume films with alot of action might have a very low resolution, if auto res is switched on, and the set size is fairly low (eg 700mb). previous post-i should use 'like' instead of 'prefer'- far less argumentative!? *groan!* :) lol. thanks for your help

[yetanotherid]

For the purpose for which you're converting, and given the fact you don't want to keep the converted video, if it was me I'd not bother with file size and 2 pass encoding. I'd probably pick a fixed resolution of between 576 and 640 and run a single pass conversion with the quality set at 70 or 75%. I guess that's up to you and how good you want it to look. I'd also go for an ABR 128kbps MP3, unless your laptop has exceptional speakers.

My logic would be to pick an acceptable resolution and quality, run a single pass encode with it, and let the file size be what it needs to be. Unless you're really hard up for hard drive space on the laptop you're going to delete the AVI anyway and you'll save yourself a considerable amount of converting time while the time taken to copy the file to the laptop won't increase anywhere nearly as much.

As you said, a 700MB movie with a lot of action is probably not going to have as high a resolution or look as good as a 700MB movie which doesn't. So once again I'd not be worrying about a 700MB parameter and go with a quality one instead. If for example, a resolution of 576 at a quality setting of 70% gives you good enough quality for laptop viewing then I'd guess a good percentage of your conversions aren't going to be much off 700MB anyway, but while the action films might grow in size a bit their quality won't drop. And you'll save yourself a lot of time converting.

[CWR03]

I would agree, decide on a quality setting rather than a set filesize.

As far as resolution, again I'll say that it's a matter of perception. Why not do a few tests at different sizes and decide what looks best to you? Asking what others like in a resolution is like asking an opinion on a movie - everyone's will be different, and only you can decide if you will like it or not by watching it yourself. Yes, you can gather a bunch of different opinions and go with the majority, but you open the room for a public debate about the movie which can lead to argument.

I'll tell you what I do when encoding - I prefer 2-pass fixed filesize, but my needs are totally different from yours. I size movies to fit either 2 or 3 to a standard DVD with no wasted space on the disk, but plenty of extra bitrate so the quality is as good as I can get. Whenever possible I keep the original width (because I don't like to lose detail) and use a fast resizer. I keep copies of these encodes on my media PC and stored on disk since I may have up to 20 hours invested in the encoding. I keep AC3 audio unless the original is 2-channel stereo.

[citanuL]

It might help to think of your target resolution as total pixels for which you have an acceptable range. For example, it seems popular to shoot for resolutions around 200,000 total pixels for dvd sources, such as, encoding a 720x480 4:3 movie at 512x384 which is 196608 pixels.