AVI in VirtualDubMod video quality question.

[scott274]

I had a movie file in .avi format. When this AVI was opened in VirtualDub, got the error..

[!] AVI: Variable bitrate (VBR) audio detected. VBR audio in AVI is
non-standard and you may encounter sync errors up to 0ms when attempting
to extract WAV files or processing the audio in Direct Stream Copy mode.
Full Processing mode is recommended to decompress or recompress the audio.
(bitrate: 128.0 ± 0.1 kbps)

To solve this problem did the following things..
1. Opened the AVI in TMPGEnc and got an uncompressed PCM wave output (.wav)
2. Then opened the AVI in VirtualDubMod and clicked No to the similar "VBR audio detected" warning.
3. Under Video tab selected "Direct Stream Copy"
4. Under Streams tab selected "Stream list". Selected the existing MP3 VBR audio stream and disabled it. Then clicked "Add" and imported the uncompressed PCM .wav file and selecting it, pressed OK.
5. Then under File tab selected "Save As..." and saved the AVI to a new folder.

But when I played this new AVI, I noticed that the video quality was slightly less than the original AVI when played in fullscreen. Does anyone know where the video quality was lost. I thought selecting "Direct Stream Copy" means video is not compressed and remains unchanged, isn't it. Is there any way to add the wave audio in the original AVI without losing any video quality as I was intending to do.

After this I intend to cut the AVI into two parts (probably in VDubMod) and then encode each part to Mpeg in Mainconcept.

[jagabo]

If you did exactly what you said (Video -> Direct stream copy) no video quality was lost. Did you have two media players open at the same time when you were judging quality? That might cause one to look worse than the other (only one player at a time can use the graphics card's video overlay feature which generally gives better video image quality than Windows GDI).

But there are two simpler solutions to your real problem.

When VirtualDubMod gives you the warning about VBR audio, answer "no". 90 percent of the time this works. You can Direct Stream Copy the video and audio with no problems.

Use a recent beta version of VirtualDub. It will still give you a warning but it handles VBR audio.

[scott274]

Uh.. I had another shifty at it and the video quality seemed fine after all I guess i was comparing the original AVI and the new one side by side and one of them (unfortunately the new one) looked slightly bad in quality.

Just confirming, I just cut the audio improved AVI in VDubMod. Set markin at start and markout at the middle, selected "Direct Stream Copy" under both Video & audio tabs and then "Save as..." under File tab (to AVI). The cut AVI output video and audio quality will be the same as the original isn't it. It looks fine here at the moment.

And further now when i encode the cut AVIs in Mainconcept to Mpegs and author in VCDgear to play in my player, I mostly won't have any audio sync problems later on will I (I mean most probably due to bad source etc). Just your thoughts on this please..

[jagabo]

Just confirming, I just cut the audio improved AVI in VDubMod. Set markin at start and markout at the middle, selected "Direct Stream Copy" under both Video & audio tabs and then "Save as..." under File tab (to AVI). The cut AVI output video and audio quality will be the same as the original isn't it.

Yes, the video and audio are not reencoded in Direct Stream Copy mode so there will be no change in quality. I recommend you mark in/out on keyframes only when doing this.

And further now when i encode the cut AVIs in Mainconcept to Mpegs and author in VCDgear to play in my player, I mostly won't have any audio sync problems later on will I

If the later software would work with the original file it should work with the segmented files.

[scott274]

How to differentiate between keyframes and nonkeyframes. In first cut, I have put the mark in at the very start and markout about halfway through the movie just before a scene changed completely to a new one.

Another thing is that I just ran the AVI in GSpot and I got "codecs not installed" in the specs. Earlier while getting a wave output, when the AVI was opened in TMPGenc, it gave me some error like "only the audio can be opened and not the video". Then I installed K-Lite mega codec pack 3.9.0 and later could open the AVI in TMPGenc without any error messages. But Gspot still gives these following specs..
http://i91.photobucket.com/albums/k292/abs724/Screencaps/LiarLiaroriginalsource7-20-2008-142.jpg

Should I still go ahead with the Mpeg encoding in Mainconcept.

[redwudz]

Codec packs can cause damage to existing codecs and install unnecessary and older versions of codecs. Not really recommended. And uninstalling them may cause further problems. Better to just install the codecs you need. The latest Xvid codec is 1.1.3

A better choice than a codec pack is ffdshow. It includes the Xvid codec, but doesn't cause damage like a codec pack can.

In VirtualDub, you can jump to the keyframes by using the yellow keyframe button at the bottom of the screen. But Xvid/Divx have the keyframes set by default to about every 300 frames. This is one reason frame accurate editing is difficult with a highly compressed format like Xvid/Divx and others. You can use the newest version of VirtualDub with the 'smart rendering' feature on. This will let you cut where you want and only re-encode at the cut points.

[jagabo]

FMP4 is an unusual fourcc code. I suggest you user Avi fourcc code changer and change it to XVID.

The easiest way to locate keyframes in VirtualDub is hold down one of the shift keys while you move the seek bar or press the arrow keys -- it will only stop on keyframes. You can identify keyframes by a little [K] that appears next to the frame number information at the bottom of the window.

[scott274]

FMP4 is an unusual fourcc code. I suggest you user Avi fourcc code changer and change it to XVID.

Will doing this change the original AVI video quality.

And thanks redwudz for your advice. Will download Xvid codec and ffdshow and try each one seperately to analyse in Gspot later and report back here soon.

[jagabo]

FMP4 is an unusual fourcc code. I suggest you user Avi fourcc code changer and change it to XVID.

Will doing this change the original AVI video quality.

No. The fourcc is simply a four letter code that identifies what codec was used to create the file (and hence, what codec to use to play it back). I've never seen FMP4 before. Make a backup copy before you change the file.

[scott274]

And after importing the AVI (original backuped) in AVI FourCC Code Changer,
what should I choose under "FourCC Description Code" (other options here are mp41, mp42, mp43 & DIV4) and what should I choose under "FourCC Used Codec" (other option are MP41, MP42, MP43 & DIV3) before pressing "apply".

Edit: One more different question before I leave the net for today. Now that I have cut the AVI movie into two parts without changing the audio/video quality, I just found out that I would like to delete a small scene (adult) from the second part AVI. Can this be done in VirtualDubMod (or other reliable application if not), again without changing the output audio & video quality.

[jagabo]

Fourcc changer: set the top one to "xvid" and the bottom one to "XVID". Type them in, don't use the pulldowns.

You can delete a scene by marking in and marking out around it (on keyframes) then hitting the Del key or Edit -> Cut. Then save as AVI (direct stream copy mode).

If you want more accurate cutting use a recent VirtualDub beta with Smart Rendering. It gives you frame accurate cuts and only reencodes cut GOPs (the distance between keyframes). The rest of the video is direct stream copied.

[DarrellS]

If you want more accurate cutting use a recent VirtualDub beta with Smart Rendering.

VirtualDub 1.8.2 is now posted as the new stable release.

32bit version...

http://prdownloads.sourceforge.net/virtualdub/VirtualDub-1.8.2.zip?download

64bit version...

http://prdownloads.sourceforge.net/virtualdub/VirtualDub-1.8.2-AMD64.zip?download

Latest beta release...

http://www.virtualdub.org/beta/VirtualDub-1.8.2-test6.zip
http://www.virtualdub.org/beta/VirtualDub-1.8.2-test6-AMD64.zip

fcchandler has a new MPEG2 plug-in also, MPEG-2 plugin v2.8...

http://fcchandler.home.comcast.net/Plugins/MPEG2

[scott274]

Thanks darrell for virtualdub 1.8.2 stable I was using 1.7.8 so far.

@jagabo,
I processed the AVI in FourCC code changer by typing in "xvid" (top) and "XVID" (bottom) and pressing apply. Got message "FourCC code has been set".
I played the AVI and it started fine (didn't go through the whole movie though but it should be fine right) and even Gspot specs now says "codecs installed".
Now if I uninstall K-lite mega codec pack and just install the Xvid codec or FFdshow as redwudz suggested, shall I consider the cut AVIs (Smart Rendering enabled) as healthy and go ahead with encoding to Mpegs in Mainconcept.

[jagabo]

Now if I uninstall K-lite mega codec pack and just install the Xvid codec or FFdshow as redwudz suggested, shall I consider the cut AVIs (Smart Rendering enabled) as healthy and go ahead with encoding to Mpegs in Mainconcept.

K-lite may have installed other codecs that you need. AC3 ACM for example. So you may have to download and install that. Other than that you should be fine.

[scott274]

Since redwudz strongly advised me against using any codec packs, next time I will only seperately install AC3 ACM codec alongwith FFdshow.

And I feel he was right about uninstalling the codec pack causing further problems too. Just uninstalled the K-Lite codec pack and reinstalled FFdshow and AC3 ACM. Gspot specs say "codecs installed" but when I try to play the AVI in windows media player it has started giving me an error, "xvidcore.dll not found" before playing.

Anyways, it's about time I did my two monthly format of the primary drive with Norton Ghost 03. So later on I will only install FFdshow and AC3 ACM codec and hope everything will be fine for me to go ahead with encoding the AVIs and authoring the compliant Mpegs.

Thanks friends Jagabo, Redwudz & Darrell for helping me out with my AVI problems.

[jagabo]

Reinstall Xvid.

[scott274]

You mean Xvid codec 1.1.3, yeah window media player has stopped giving me that error now.
I thought the Xvid codec was included in FFdshow, Hmm.. now where did I hear that!!

[jagabo]

Ffshow does include an Xvid DirectShow decoder. Mabye it wasn't enabled.