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Subject: Re: AC3 files not playing from where they stopped

Re: AC3 files not playing from where they stopped

From: Andrew Hart <ahart_at_dim.uchile.cl>
Date: Tue, 25 Jul 2006 18:16:32 -0400

I'll answer this question, but it is the only time I will respond
on-list in relation to ripping the audio from DVD's, unless the list
moderators deem it to be of further interest. This topic is starting
to get away from Rockbox somewhat and I don't wish to clutter the
list with off-topic posts.

Of course, I can always be contacted off-list for further information.

There are numerous programs for ripping the audio from DVD's. The
three with which I have experience are

DVD Extractor
DVD Audio Ripper
DVD Decryptor

The first two are commercial products while the last one was free for
download at the time I downloaded it, but it may be commercial now.

They are all fairly accessible with screen reading software, but I
found DVD Extractor and DVD Decryptor easier to use from a user
interface point of view. If you just want to rip audio into mp3 or
ogg format without too much mucking around, DVD Extractor is the
simplest and least technical to use. When I trialed DVD Audio
Ripper, it had fewer options for ripping and only allowed constant
bit rate mp3 or wave rips. Also, there was something funny in the
interface I never got the hang of with selecting exactly whatI wanted
to extract. If you're wanting to pay for one, I think DVD Extractor
is where you'd want to put your money.

On the other hand, DVD Decryptor has a highly accessible interface
but is much more technical to use. In fact, DVD Decryptor is not
just an audio ripper. It is for removing the encryption from DVD's
so they can be backed up or copied to hard drives, etc. It just so
happens that it can be used to nab the audio from DVD's as well and
this is what I use it for.

I won't go into details of how to use it, but it extracts the audio
streams from the DVD and puts them in files on your hard disk. if
the DVD was authored using AC3, the audio files will be AC3
files. if the DVD was authored with MPEG, then the audio files will
most probably end up being mp2 files. DVD's with mp2-authored audio
streams are frequently pirated, so be ware. To the best of my
knowledge, commercially pressed DVD's always use AC3 audio
streams. So, supposing you have AC3 files, You then have to convert
the AC3 into wave, mp3, flac, ogg or whatever format you like. Or,
you can leave them as AC3, download them to your player and Rockbox
will happily play them for you.

You should be aware that AC3 files are much larger than what people
normally would use. As an example, the AC3 audio for a 2 hour movie
will generally be around 400-500 megabytes in size while a 40 minute
TV episode will have around 140-170 megabytes of AC3 audio per audio stream.

The neat thing about having the AC3 stream itself is that you can
downmix it to 2-channel Dulby Prologic which is great if you happen
to have a Dulby Prologic decoder on a sound card, etc. Because then
you can play the same file on a jukebox or run it through a
DPL-capable sound card on a computer and recapture some of the 360
degree surround effect. it ain't perfect, but it's nice to be able
to do that with a single file.

In any case, having the AC3 itself gives you total control over the
conversion to other formats; you're not limited to what the DVD
ripping software is able to do. You can choose precisely the size
vs. quality trade-off you want.

Hth,
Andrew.

At 17:02 25-07-2006, you wrote:
>Hi,
>This sounds perfectly interesting! But what software do you use for
>ripping the DVD's? How accessible do you find the software?
>
>----- Original Message ----- From: "Andrew Hart" <ahart_at_dim.uchile.cl>
>To: "Rockbox" <rockbox_at_cool.haxx.se>
>Sent: Tuesday, July 25, 2006 3:43 PM
>Subject: Re: AC3 files not playing from where they stopped
>
>
>>Hi Brandon,
>>
>>I simply rip the audio off DVD's.
>>
>>Being blind, the visual component doesn't help much, so I don't
>>miss it. When I'm too lazy or can't wait to listen to the DVD, I
>>just extract the AC3 audio stream I want, dump it onto the player
>>and listen away. However, normally I will transcode the AC3 into
>>mp3 or ogg format (which are significantly smaller files).
>>
>>I find using Rockbox on my jukebox with a portable amp and decent
>>headphones to listen to DVD audio is much nicer than fighting with
>>the awful user interfaces in programs like PowerDVD. Plus I'm not
>>tied to the computer.
>>
>>Pressed DVD's use the A52 encoding standard which is better known
>>as AC3. AC3 generally contains 5.1 channels, 5 for centre, front
>>left, front right, rear left and rear right speakers, plus a .1
>>derived from the other 5 for feeding to a subwofer. The AC3 codec
>>in Rockbox takes all 5.1 channels and downmixes them to two stereo
>>channels on the fly. Very cool indeed.
>>
>>Hth,
>>Andrew.
>>
>>At 15:07 25-07-2006, you wrote:
>>>Hi Andrew,
>>>How exactly did you get AC3 files anyway? My understanding was that these
>>>were generally DVD Audio, am I correct?
>>>
>>>Brandon Hicks
>>>Email: reyuth1010_at_gmail.com
>>>Skype: callto://reyuth
>>>msn: silverdart12_at_hotmail.com
>>
>>
Received on 2006-07-26


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