AUDIO/VIDEO out of Sync (NEW FINDINGS - ALL SIZES)

[Adrian Edmonds]

For some reason my reply to original post keeps showing up deleted. Thats okay - NEW FINDINGS...

 We found the problem - In order to help you fix it. This is in regards to larger files being out of sync. It's NOT JUST larger Videos. It’s all videos. Smaller files are out of sync by milliseconds, so eyes don't detect it. Video software does. First let’s review.

 1) VERIFIED IT’S NOT THE VIDEO - Went to several movie sites and downloaded full 3 different movies - All are out of sync.

 2) ISOLATED IT IS "Video DownloadHelper" - Used 3 different video down loaders for the aforementioned videos and the other 2 Firefox AddOns (HLS Downloader, CocoCut); the Video/Audio are perfectly in sync.

 3) ORIGINAL ASSUMPTION that it's just longer files - is incorrect. It’s all sizes. Longer files it becomes more prominent (detectable to the human eye) because it is over a second or two off. Smaller files are just milliseconds, harder to detect.

 4) PROBLEM appears to be dropping Video frames during process Before conversion to MP4 or During the MP4 conversion process.

 VERIFIED Number 4.  The image attached is Video editing software. This is the end of the files. ABOVE is from CocoCut (Firefox addon). Below is "Video Downloadhelp"

 YOU WILL NOTE: the Video is NOT matching the audio in length for a (2 hour and 35-minute move. To be exact = 2:35:40:23). By the 2 hour mark you are losing a little over seconds of video - the human eye can see.  FOR smaller movies (less than 60 minutes) you are losing milliseconds, the eye doesn't detect.

WHEREAS: Audio and Video for CocoCut (and others I tested) are an exact match.

 

 Analysis - Culprit.

 ACLAP VDHCoApp - If this only detects the stream/video your problem is not here. IF it is capturing frames and audio to send to Video Download helper then it could be preprocess issue.

 IF NOT - then it's in "Video Download helper" processing to MP4.

 I HOPE this shows where your problem is, and you have a chance to fix said problem. I prefer to use "Video DownloadHelper". It's cleaner.

 

[Wild Willy]

It seems I am the victim of Google's capricious censorship policy, as you can see from
the message deletion notifications above. I tried sending this post to the thread using
E-mail but it got deleted. So I tried posting it the old-fashioned way & that also got
deleted. So now I'm trying via E-mail again but I've hived off the URLs into an
attachment. Let's see if this works.

Adrian sent me a couple of private messages because he thought I'm the VDH developer.
No, I'm just another user. He gave me these URLs:

(see attached file)

I went to the first site & did a search for the movie "Eternals." VDH downloaded it
without difficulty. It's about a 2.5 hour movie, the file is about 2G, & it took 20
minutes to download. It's not the sort of movie I would watch so I just skimmed through
it looking for places where you could see people's faces while they were talking. Early
on, everything looked in synch. But by about 45 minutes in, things were noticeably out
of synch. Like I say, I didn't actually sit & watch it so I didn't verify that the
problem got worse as the movie went on. But I can confirm that there does appear to be a
problem of synchronization with this movie.

I then wanted to download the movie using ffmpeg following the technique you can find
over here:

https://groups.google.com/g/video-downloadhelper-q-and-a/c/BzPLK2YyL-s

Look for the reference to an alternative technique for downloading content that VDH fails
to download.

The problem was that I couldn't get the site to play the video a second time. It caused
my CPU usage to soar to about 12%, enough to get the case fans blowing up a hurricane. I
kept getting these new windows opening on sites I have blocked in my HOSTS file. But
that would happen about every 5 minutes. Something was going on but it was taking
Firefox forever to honor whatever the requests were. This sort of site is almost
certainly supported by advertising & I think I was just seeing that. But however they've
got their HTML coded, Firefox doesn't seem to like it. It appears I was extremely lucky
to get into the movie the first time. So I have not been able to try my ffmpeg
technique. I have saved the direct URL of the movie, bypassing the search:

https://www5.himovies.to/watch-movie/eternals-73555.4792213

I may try again in the coming days. I've spent about 2 hours just trying to get the web
page to play the movie without success. I can't spend any more time on this now.

Oh. And in the middle of all this, Firefox updated to 96.0.2. I doubt that had any
impact.

Maybe somebody else can have better luck with this than I did. I suppose I could try one
of the other sites. But I would have to download the movie from there again using VDH &
then try ffmpeg on that site. I need to do the download of the same movie from the same
site using the 2 tools. Just downloading the movie from a different site with ffmpeg
when I already have the movie from the first site would not be a proper test.

[Wild Willy]

Forgot to mention that this thread here is a continuation of this other thread:

https://groups.google.com/g/video-downloadhelper-q-and-a/c/Qj_6IkDb1kY

That one was censoring Adrian's posts so he managed to start this one.  The 2 threads need to refer to each other.  I've already taken care of the other one.

[Wild Willy]

I recorded a live stream of golf this afternoon. I got a file of type MP4 of duration 4
hours. The audio & video were out of synch from the start. I had to use the delay
feature of VLC to shift the audio later by 250ms. This stayed constant for most of the
video. Toward the end, I adjusted the delay to 300ms. This is a small fraction of a
second. As I said in an earlier post, I believe this is a problem in the source. This
lack of synchronization is visible in the original broadcast via cable TV. I just wish I
could adjust broadcasts the way I can adjust the sync in VLC.

So the problem of bad sync, if it is caused by VDH, does not happen on all content. I
download things of varying lengths from various sites pretty much every day & I don't
notice the kind of severe sync problems we're seeing with this "Eternals" movie. I have
to say that the quality of this movie is low, meaning the bit rates are low. Sure, it's
1920x1080 but no way it's HD. The bit rates are in the 1500kbps range. This is probably
to be expected from a site like this that offers movies for free. You get rather poor
quality content in exchange for the absence of having to pay for it & for having to
endure endless advertising. I'm not sure what can be done about this. I just wish I
could have gotten the site to cooperate with me to let me try downloading the movie with
ffmpeg. I haven't forgotten about this but I'm not rushing to try it again.

[Wild Willy]

Since that first successful visit to Himovies, it has turned into a completely failing
web site. Opening the page for the movie just makes my CPU usage spike up, the page does
not load, I can't even scroll it properly.

So I cut my losses & tried the second site . . . whose name I won't actually quote since
Google might censor it. It's in the attachment I posted earlier. The name starts with
123. First I launched the VDH download. This was getting about 2.5 million bytes per
second download speed. While that was running, I fooled around looking for a manifest in
the Firefox Network Monitor. I didn't see a master manifest but there was a stream
manifest. Running that manifest through ffprobe told me it was MP4 with both video &
audio, although the resolution was only 1280x534. That's kind of lousy but I didn't see
any way to tell the web site what resolution I wanted. When I saw that, I went back to
the web page & looked at the VDH information to see what resolution it was quoting. It
wasn't showing a resolution. But it was showing an ever growing list of small variants,
at which point I realized I had not stopped playback of the video in the web page. So I
stopped it. While the VDH download continued, I launched ffmpeg for what I assumed was
the same stream. As we've already established, this is a movie of about 2 & 1/2 hours.
The ffmpeg download stopped because of a corrupt packet after getting about 22 minutes of
the movie.

At this point, I inspected the VDH download, which had finished after a mere 17 minutes
with a file of size 1.4G (compared to the 2G of my earlier download at the higher
resolution). Although VDH never reported a resolution, it was the same 1280x534 that
ffprobe had found. The bit rates were, as expected, rather low. Once again, I just
skimmed through it looking for places where faces were clearly visible while they were
talking. It seemed like it took longer into the movie before it became noticeable but
the audio gradually lagged more & more behind the video as it played until it was
actually kind of distracting.

At this point, I retried my ffmpeg download. For some reason, the ffmpeg downloads were
getting something in the range of only 1.5-2.0 million bytes per second download speed,
rather slower than the VDH speed. By this time, I had closed all my browser windows,
since ffmpeg is its own process, not relying on Firefox in any way. I don't know why
ffmpeg would have been slower. It certainly wasn't competing this second time with VDH.
But my Internet bandwidth is way higher than that & could have taken several concurrent
instances of both VDH & ffmpeg downloads with ease. The only limitation would have been
whatever throttling the serving site might have been imposing. But it doesn't seem like
running against VDH or running by itself made any difference to the download speed ffmpeg
was getting from the server. This second attempt to download with ffmpeg succeeded
without any corrupt packets after 54 minutes. Clearly, that was a transient error the
first time. This file was 1.39G compared to the 1.40G file VDH got. The ffmpeg MP4 was
5 seconds longer than the VDH download. These variations are small but unexpected.
Otherwise, the resolution, bit rates, & frame rate were the same.

I skimmed through the movie as ffmpeg got it more carefully than I did for the VDH
versions. The synch between audio & video is perfect all the way to the end. And all
the closing credits appeared to be there in this ffmpeg download. I still didn't watch
it all & it still doesn't look like the kind of movie that interests me in the least.
But I think I've proven that in the case of these movies, VDH is introducing some kind of
audio lag. But it is not something that occurs with everything VDH downloads. I don't
see this kind of problem with other content I've downloaded. The only comparable things
I've used VDH to download are the livestreams of golf. They are typically even longer
than this movie & those do not suffer from the progressive audio lag that this movie
does. I am quite convinced that the tiny audio advance (it's an advance rather than a
lag) that I see with the golf is in the original source. And the advance does not vary
much throughout a recorded broadcast. So curing this lag problem in VDH is going to take
special attention to these specific movies. I wouldn't hold my breath waiting for this
investigation to occur. I suggest you continue to use your other tools that you have
already mentioned for these cases. You could even use ffmpeg, as I have. These movies
appear to constitute one of those cases in which VDH is not the right tool for the job.
Today. In the future? We'll see.

[mjs]

I was looking for something on the forum where I found this discussion. Adrian if you're still using Video downloadhelper have you tried

enabling the setting HLS as M2TS in the settings page. Does it still exhibit the problem or does it fix it with the setting enabled.