Is there any reason to encode DVDs to AC3 if no digital speakers present?

[duragezic]

I've been ripping some DVDs and converting to xvid avi with AutoGK, but I realized I've been encoding to AC3/DTS audio in all of the ones where I set quality/size to 1400mb (usually did it for movies I liked a lot and were longer) rather than the fairly common 700mb.

I left audio on Auto for every encode, which for 700mb movies means mp3 VBR @ 128kbps but for the 1400mb Auto means AC3/DTS which IIRC is 400+kbps bitrate. So am I wasting space that could be better used on video quality IF all I have for audio is a Audigy Platinum eX hooked up to Logitech X-530 speakers ($50ish speakers)? I think I lose 5.1 with mp3 but I normally use CMSS2 to upmix anyway.

 

[SynthDude2001]

If you care about keeping the 5.1 sound (and it sounds like you don't), then the AC3 is worth it even if you have the X-530's (like I do). If you'll be satisfied with stereo/stereo upmixing, I guess you might as well save space if that's what you're looking to do.

 

[Evander]

I bit off topic, but I recently stopped using autoGK in favor of Fairuse Wizard:
http://www.fairusewizard.com/lang_en/fa...vx_xvid_backup_tool_light_edition.html
The reason is b/c unlike autogk it supports the better x264 codec, which according to some sites gives up to 20% better quality than xvid/divx at the same bitrate (with the downside being increased cpu decoder usage). And I use ogg for audio at 36kbps and it sounds great.

 

[duragezic]

Don't Nvidia cards have GPU acceleration for encoding x264? Is the quality really worth it?

 

[SynthDude2001]

Originally posted by: duragezic
Don't Nvidia cards have GPU acceleration for encoding x264? Is the quality really worth it?

No, they don't. Some of them have acceleration for decoding x264 (h.264 more generally) though - though if you have an original 6800 series card in AGP like I do, you're screwed and won't get that support.

I haven't done any extensive quality comparisons between xvid and x264 myself, but I was impressed enough by x264 to make it the only codec I'll bother to use when I encode video from HDTV sources. To my eyes, two-pass encoding at 3000kbps produced an identical file to the original transport stream which was 7-8mbps. (This was 720p/60fps source material)

CPU requirements are pretty high for decoding though, as mentioned above. One of my friends who still has an Athlon XP can't seem to play back my 720p/24fps encodes, though another with a similar CPU (though ~200MHz faster) can play it back fine with no more than 75-85% CPU usage. 1080p is pretty much out of the question for anyone with a single-core CPU though (unless the aforementioned Nvidia acceleration really works, which I have no way of testing myself). But since it sounds like you're just doing SD/DVD material anyway, playback should be no problem for anyone with even a somewhat modern system. I would recommend at least giving x264 a shot...I really like it.

 

[duragezic]

Ok I'm convince! I got FairUse and I'll try my next encode with x264.

And I think I'll stick to AC3 still. I'd like to preserve the 5.1 sound plus in the future I may have better speakers or the encodes might be played in a home theater with a nice audio setup (just dreaming now... )


edit: I guess space isn't a huge concern. I just need to get off my ass and order a DVD burner and some media so I can burn all this stuff to DVD. I encode some to 1.4gb and others to 700mb so I could fit a couple of each per DVD disc (at this point they'd only be for PC playback or with Xbox media center).

 

[Slick5150]

h.264 is nice, but I'm still using XviD as XBMC can't playback h.264..

(well, it can, but the Xbox doesn't have enough power to do it with much success)

 

[jcmuse]

I would say use AC3.. but not at the sacrifice of video quality. For the majority of films, 1400mb and AC3 audio will look great.... others will not (ok, they will still be watchable, but won't look as good).

 

[0roo0roo]

so if u use ac3 the video suffers..yes divx likes as much as it can get assuming u odn't lower the res so far that it maxes out. or u make the video suffer and keep full quality surround sound without a second compression and all the artifacts that adds...
not worth the trouble, just rip and split the dvd

 

[TerryMathews]

You shouldn't be judging this decision on whether you've got digital speakers or not, but whether you've got more than two speakers or not.

AC3 is an excellent audio compression scheme. The space savings you're seeing are from downsampling from 6 channels to 2.

I would say for such an insigificant space savings, keep the 6 channels of audio - once they're gone, they're gone.

I don't know of a more efficient multi-channel audio encoding scheme. If you're downsampling to 2 channels, you should be going to MP3 or OGG, and wrapping the file up in an MKV or OGM. X264 seems to be the new video codec of choice, if you're playback equipment (computer or otherwise) is powerful enough to decode it real-time.

 

[Hav0k99]

Will this app do h.264 for Ipod Video? If yes does anyone use this?

 

[MangoTBG]

If an athlon can't decode h.264 how is an ipod supposed to?

 

[SynthDude2001]

Originally posted by: MangoTBG
If an athlon can't decode h.264 how is an ipod supposed to?

You wouldn't be expecting the ipod to play 720p/1080p...