Audio Conversion.

[spud1980]

Hi guys,

I know that the first step in Gnot is creating a DVD2AVI project file but I still do not know the exact purpose of that except it's to determine what frame rate and whether it's running in PAL or NTSC.

I think (not too sure, cuz I'm kinda using robot4rip now), while creating the project file it extract the ac3 file from the vobs and demuxes it? What is demuxing and why do you have to demux?

And later on you go on and do the bitrate thingy and cropping, and finally you do a compression test and commence the actual encoding.

Then it demuxes the audio again? Which part of the process does the ac3 becomes a mp3? Can I set the bitrate for the mp3 to higher than 160, it seem the default settings provided in the tuts does not teach that. I know you guys are sick of newbies asking the same old darn question, I've tried to read around but still do not get it, if not maybe you can link me to a thread so I can read it up myself.
Sorry for the bother thanks in advance.

[jggimi]

I haven't used R4R, but I'll take a crack at answering your questions....I still do not know the exact purpose of that (.d2v) except it's to determine what frame rate and whether it's running in PAL or NTSC...Aside from that, it's also used for initial determination of Telecining and/or type of PAL conversion from NTSC (see www.doom9.org/ivtc-tut.htm for more info.) But from a process perspective, the .d2v project file you produce in this step is read by AviSynth to extract the MPEG-2 video stream from the VOBs, and deliver uncompressed video for other AviSynth filters during the Vdub (or Nandub with DivX 3) encoding steps....What is demuxing and why do you have to demux? VOBs contain multiple things: MPEG-2 video, all subtitles, and all soundtracks. Demuxing is the extraction of individual streams from the VOBs. The .d2v project file in AviSynth, for example, is one way of demuxing the video stream. DVD2AVI can also demux various types of soundtracks, including Dolby Digital (.ac3), MP2 (.mpa), and Linear PCM (.wav)....Then it demuxes the audio again? No, it encodes an already demuxed and selected DD soundtrack into MP3 (if you follow the guide). You can leave the audio in its original format; many people have PC's with Dolby Digital soundcards -- these folks typically leave the audio in .ac3 and select "just mux" to mux the audio and finished video together. 5.1ch DD is typically 448kbps, so those who keep .ac3 files usually use lots of CDs.Which part of the process does the ac3 becomes a mp3? If you have selected an audio track (.ac3, typically) as part of your batch job, as per the guide, the audio transcoding will be the first step, usually done by BeSweet....Can I set the bitrate for the mp3 to higher than 160, it seem the default settings provided in the tuts does not teach that.Yes, but most people's ears aren't good enough to detect differences in audio quality with higher bitrates. The higher the bitrate for audio, the lower the available bitrate for video. And there, it is easy to see the difference between high and low bitrates.

If you're encoding with DivX 5, the steps (prior to R4R) are as follows:
[list=1] Rip: extract a single angle of a single program chain from the DVD to HD (DVD Decrypter).
Create .d2v project, demux audio track(s), optional IVTC (DVD2AVI).
Setting resolutions and bitrates, cropping, IVTC, other filters.
Compression testing, back to step 3 as necessary (Vdub).[/list=1]If you're following the guide, at this point you have created your .avs scripts and are starting a batch job, which will do the following: [list=1] Transcode audio (BeSweet).
Optionally encode the end credits with really low quality (Vdub).
First pass of Video encoding (Vdub).
Second pass of video encoding (Vdub).
Muxing together finished video and transcoded audio, optionally tacking on the low-qual credits (Nandub).[/list=1] Splitting and buring to CDs is left to the user.

I hope this helped.