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  1. Member
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    The subject might seem silly to you DVD veterans, perhaps you could offer suggestions or point to the right HOWTO guide. I've read baldrick's "How to convert DVDs back to MPG files for reauthor or reedit", but I'm just not connecting the dots.

    My background is familiarity with basic video/audio editing using tools like virtualDub, Super, audacity, etc. But I am a novice when it comes to DVD editing.

    Here's what I'm trying to do. I'm trying to clean up the audio on an instructional DVD. The solution is theoretically simple: since the audio consists of one person speaking it's perfectly ok for it to be mono, i.e. the same audio on both channels. So all I need to do is duplicate the one good audio channel.

    My first stab at it using tools I'm familiar with was a partial success:
    1. demux the vobs using Super
    2. modify the wav audio using audacity
    3. mux the video and corrected audio back into vobs using virtualDub and Super

    This does in fact result in vobs that play perfectly by themselves, but the showstopper problem is that all the menus are now broken so access to individual chapters no longer works. I don't really understand how DVD titles/chapters are actually implemented as I have not found a good explanation anywhere. My guess is that VOBs cannot be simply edited (as I've done) without taking into account physical offsets that chapter navigation seems to depend upon. It seems if such a low level manual edit is done then the corresponding menu to chapter linkage needs to be updated as well.

    It would be agonizingly tedious and error prone to have to do this for all the chapters of a DVD on any edit so I'm guessing the better tools handle this. Ideally a tool would demux the vobs, cache the demuxed streams for edit, and be capable of muxing streams back into vobs without breaking the menu to chapter navigation that was present.

    I'm guessing there exists a tool or combination of tools that would accomplish this, but like I said I'm just not connecting the dots.

    Helpful suggestions are most welcome.
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  2. Hi-

    Here's the right way to do the job:

    1. Demux the VOBs using PGCDemux (making sure to check the "Demux video stream" box).
    2. Do what you want with the audio.
    3. Remux using Muxman. Add in the Celltimes.txt in File->Import Chapter. Give it a destination and "Start". Even though Muxman might seem to quit or freeze, it's still working and will give you a message when done.
    4. Open the original DVD in VobBlanker. Highlight the VTS for your video in the top screen so it appears in the bottom screen. Highlight it in the bottom screen, hit the "Replace" button to the right, and scroll to your new DVD with the fixed audio. Give it an output folder and "Process".

    You'll get back working menus and your chapters. If you have any problems along the way, just post again with your question(s).
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  3. Member
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    Originally Posted by manono
    Hi-

    Here's the right way to do the job:

    1. Demux the VOBs using PGCEdit (making sure to check the "Demux video stream" box).
    2. Do what you want with the audio.
    3. Remux using Muxman. Add in the Celltimes.txt in File->Import Chapter. Give it a destination and "Start". Even though Muxman might seem to quit or freeze, it's still working and will give you a message when done.
    4. Open the original DVD in VobBlanker. Highlight the VTS for your video in the top screen so it appears in the bottom screen. Highlight it in the bottom screen, hit the "Replace" button to the right, and scroll to your new DVD with the fixed audio. Give it an output folder and "Process".

    You'll get back working menus and your chapters. If you have any problems along the way, just post again with your question(s).
    Sorry, I can't find a "Demux video stream" box in PGCEdit. I did some googling and the "Demux video stream" box seems to be in PGCDemux. I'll try and see if I can make use of that tool.

    Thanks for the procedure. It seems conceptually straightforward, I'm just not familiar with these tools. I hope to have it figured out soon though.
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  4. Darn, got the 2 programs mixed up. And I looked in PGCDemux before writing the post, just to make sure I had the name of the "Demux video stream" box correct. Sorry, yes it's PGCDemux, and I'll go and fix the original post now. Sorry to send you on a wild goose chase.
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    Originally Posted by manono
    Darn, got the 2 programs mixed up. And I looked in PGCDemux before writing the post, just to make sure I had the name of the "Demux video stream" box correct. Sorry, yes it's PGCDemux, and I'll go and fix the original post now. Sorry to send you on a wild goose chase.
    No problem. I was able to figure it out.

    I am encountering problems with Muxman though. It seems it doesn't like muxing wav audio. When I attempt to mux with wav it immediately bombs with an error "Multiplex Operation Failed - Probably caused by excessive bitrate".
    Huh??

    Incidentally I don't like the fact that PGCDemux muxes audio to mp3 by default (I'm not even sure if the output format can be selected). In this particularly application it's fine as I don't care about lossy compression for voice. But had there been music involved I don't want an edit to diminish the quality however small the change might be. PGCDemux should demux to a lossless audio format by default if it can.
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  6. Huh??
    What was the original audio? Some sort of AC3 audio, I would guess. I would suggest reencoding your WAV audio back to the bitrate of the original AC3. For example, if the original audio was AC3 2.0 @ 192, and you've created a WAV audio @ 1536, then you've created audio with a bitrate of over 1300 kBits/Sec greater than the original. And if the max bitrate of the video is, for example, 9500, or even 9000, then by adding in the higher bitrate WAV audio, you've just made your assets non-compliant for DVD, which has a max bitrate of video, audio, subtitles, and muxing overhead of 10080.

    What to use for the WAV->AC3 conversion? Unless you have a commercial AC3 encoder available, either ffmpeg, or Aften with the EncWAVToAC3 GUI.
    Incidentally I don't like the fact that PGCDemux muxes audio to mp3
    I don't understand. PGCDemux doesn't convert anything, but gives you everything exactly as on the DVD. And there shouldn't be any MP3 audio on the DVD, as it's illegal. But if there is, and if somehow it was authored with it, don't blame PGCDemux - blame the guy that made the DVD.
    PGCDemux should demux to a lossless audio format by default if it can.
    Again, it doesn't do anything to any of the assets. It just gives you what was on the DVD. You can have the VOBs decode to WAV audio at the same time as getting the audio and video by loading the VOBs in DGIndex if you like, setting the audio to Audio->Output Method->Decode AC3 Track To WAV, and then File->Save Project and Demux Video.
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    Originally Posted by manono
    Huh??
    What was the original audio? Some sort of AC3 audio, I would guess. I would suggest reencoding your WAV audio back to the bitrate of the original AC3. For example, if the original audio was AC3 2.0 @ 192, and you've created a WAV audio @ 1536, then you've created audio with a bitrate of over 1300 kBits/Sec greater than the original. And if the max bitrate of the video is, for example, 9500, or even 9000, then by adding in the higher bitrate WAV audio, you've just made your assets non-compliant for DVD, which has a max bitrate of video, audio, subtitles, and muxing overhead of 10080.

    What to use for the WAV->AC3 conversion? Unless you have a commercial AC3 encoder available, either ffmpeg, or Aften with the EncWAVToAC3 GUI.
    Incidentally I don't like the fact that PGCDemux muxes audio to mp3
    I don't understand. PGCDemux doesn't convert anything, but gives you everything exactly as on the DVD. And there shouldn't be any MP3 audio on the DVD, as it's illegal. But if there is, and if somehow it was authored with it, don't blame PGCDemux - blame the guy that made the DVD.
    PGCDemux should demux to a lossless audio format by default if it can.
    Again, it doesn't do anything to any of the assets. It just gives you what was on the DVD. You can have the VOBs decode to WAV audio at the same time as getting the audio and video by loading the VOBs in DGIndex if you like, setting the audio to Audio->Output Method->Decode AC3 Track To WAV, and then File->Save Project and Demux Video.
    Here's the data on the original (as reported by Media Player Classic):
    MPEG2 Video 720x480 (4:3) 29.97fps 8000Kbps [Video]
    MPEG Audio 48000Hz stereo 384Kbps [Audio]

    Ok, I tried AC3 and it appears to be happily muxing. Next up VobBlanker.

    That was a typo btw, I meant to say mpeg but apparently had mp3 on the brain. The problem I was having with processing the audio as mpeg was that audacity reads this format, but doesn't write it. So I was writing wav and converting to mpeg using Super. I now see how I hosed this up. The bitrate setting from prior use of Super was not preserved. Ooops. That's the exact problem you pointed out.
    Thanks.
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    'Hope you didn't read my false alarm.

    The process was successful! Not sure if my audio editing achieved the intended result, but that's a separate issue. Your DVD editing procedure was spot on!


    Many thanks.
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  9. You're welcome. Oh, MPEG audio. I guess that's MP2. Not really accepted in NTSC DVDs, but most players can play it OK. AC3 would be better.
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    Originally Posted by manono
    You're welcome. Oh, MPEG audio. I guess that's MP2. Not really accepted in NTSC DVDs, but most players can play it OK. AC3 would be better.
    I don't know why NTSC vs. PAL would make a difference as to which compression scheme. I've seen plenty of specs for NTSC players listing mpeg as a supported format. I was also under the impression that mpeg preceeded implementation of AC3 (Dolby). It certainly is possible to have stereo without AC3. OTOH, DVD technology is new enough so that all players could have support for AC3 from the get go even without their specs explicitly listing it. I need to get better acquainted with the history of DVD technology.
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