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Main version 2.6 / VOB resizing and compression
« Last post by Thyco2501 on May 15, 2018, 01:58:59 PM »
First of all, this is my first post here so hello!

I'm currently trying to convert VOBs into MP4s, but it's somewhat tricky. The resolution of VOBs is 720x480 with anamorphic aspect ratio (pretty sure this is true for all NTSC VOBs), and it has to be changed to 853x480 to maintain proper aspect ratio. The problem is that you can't use odd numbers when resizing so the only options are 852 or 854, but you can't really use either if you want to maintain mod16. This basically means that you have to use 848x480 or 864x480. Correct me if I'm wrong, but I think the first one is the lesser of two evils because it alters the aspect ratio by only 0,59% (or 5 pixels) as opposed to 1,29% (or 11 pixels). That's when you squeeze the video, but I'd like to try cropping it now, and this is where I need help. I intend to do the following, but it's probably all wrong:

1. Resize the video to 852x480 or 854x480 (I'm leaning towards the first option).
2. Crop pixes from the sides so that the resolution becomes 848x480.
3. Resize the video to 848x480 (the same as in step #2) just so that the resize filter gets to work with mod16.

My questions are (please keep in mind that I'm not an expert when it comes to this stuff by any means):

1. Is there any preference between 852x480 or 854x480?
2. Is using the resize filter twice during the same conversion a bad idea? Does it lower the overall quality?
3. Should I even resize a second time just so that the filter gets to work with mod16?
4. How important is it to maintain mod16 for both resolution values?
5. How exactly does mod16 improve compression?

Finally, if you have any tips concerning VOB conversion as well as improving quality and/or keeping file size low, I sure could use them!
Windows / Re: Do I have an audio desync after a split?
« Last post by Bruno Augusto on May 15, 2018, 11:23:02 AM »
Alright, I've downloaded the latest version (May, 4th) and tried again. One of the videos reporting the mentioned delay still are but instead of -100ms I've got -65ms which, in a different scene that I finally could notice if it was delayed or not, now became unnoticeable.

Something that peaked my attention while testing this nightly build was that the file with the... "left" portion of the video, I mean, from the start and up to the length of the first episode, did not have this so-called delay, only the "right" one, something around the middle of the video and up to the end of the file.

Because I'll need to edit the resulting files through Premiere for some linear adjustments, like adding missing vignettes, I always have to work with at least MP4 instead of MKV (because Adobe is picky :p) and when using the MP4 Muxer, none of the resulting files had any delay. \o/

Anyway, it seems the issue has been solved but I thought this bit of information could be useful for the future, be it as a reference or any possible update.

I'm using 2.7.0 on Windows, and have a few suggestions:

1. Add a "Check for Update" item in the menu, as an easy way to know if a more recent release is available

2. In the About dialog, add the precise release number, make it selectable as an easy way to copy/paste, and add a hyperlink to the site so users don't have to manually type the URL in their browser

3. More important: Make it possible to select multiple segments with the A/B buttons: Currently, when I need to trim a video by extracting multiple parts, I have to resort to Shotcut, which is slower than AviDemux.

Windows / Re: Do I have an audio desync after a split?
« Last post by eumagga0x2a on May 14, 2018, 10:15:58 PM »
Presumably there is no desync, but please use the latest nightly, some issues resulting in excessive video delay have been fixed since the last release (2.7.0).

Windows / Re: Audio Bug at Video Start
« Last post by eumagga0x2a on May 14, 2018, 10:13:22 PM »
Would the next nightly have it implemented?

Windows / Do I have an audio desync after a split?
« Last post by Bruno Augusto on May 14, 2018, 04:24:03 PM »
I never used AviDemux before and recently, when looking to split an MKV into two parts, I read it could be done with it.

Despite the slight sluggishness I had with the seek bar, I could split without any quality loss and very fast, however when I checked both the original file and the split one with MediaInfo, the one I made reported Delay relative to video: -110 ms

I played the video, at different moments, and I couldn't notice the audio delayed as indicated. I also tried to compensate these -100 with VLC controls and, once again, apparently no differences.

So, does this entry means I have a real delay or not?

In the event you need a sample of the file, any of these, originally found in a Reddit post will do.

Thank you for your time
Windows / Re: Audio Bug at Video Start
« Last post by Cormy1 on May 14, 2018, 12:28:15 PM »
How would I go about checking if that fix has been applied in a particular release?
Would the next nightly have it implemented?
Thank you! And also thanks for fixing the comparison; my flags check was buggy.
I pushed the patch with minor changes, thank you.
A52_DOLBY means that the audio is not only stereo, but also contains Dolby Surround information (analogue matrix system that encodes surround sound in two channels and is backwards compatible to stereo). When using A52_DOLBY instead of A52_STEREO for the 5.0/5.1 downmix, the surround channels are mixed a bit differently into the output downmix. Nevertheless I would prefer to always use A52_STEREO here, to not create any surround sound that did not exist in the first place and the user probably doesn't have the Dolby Surround decoder enabled on his/her surround speakers.

Currently ADM also behaves the same way when A52_STEREO or A52_DOLBY is returned by liba52dec. So from ADM side there is no need to consider which of the two formats has been detected in the first place.

Some AC-3 background:
If (and only if) an AC-3 frame contains 2.0 content, it also contains the dsurmod flag (= Dolby Surround Mode). This flag indicates whether the 2.0 content contains Dolby Surround. The difference between A52_STEREO and A52_DOLBY is just that it expresses that the Dolby Surround flag was set. And, as mentioned, the slightly different downmix from multi-channel surround.

The AC-3 spec says about the dsurmod flag:
"This information is not used by the AC-3 decoder, but may be used by other portions of the audio reproduction equipment."
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