Why sound is out of sync when capturing to AVI? (MPEG is OK)

[alex1234]

Please help me to understand why if I capture to an AVI a long scene (~ 1 hour) I've got sound out of sync with the video at the end of the file? I have no frames dropped at all.

When I capture the same scene to an MPG - no problem.

I'm using ATI TV Wonder Pro (this is NOT BT8x8 based card)

[reboot]

Have you tried capturing using an audio compression codec, such as Fraunhoffer mp3?
Raw LPCM .wav capture takes much more room, and requires the capture program to write much more data to the hard drive.

[Almost Human]

My two computers lose sync at about .2 second per hour, so at the end of a really good 2 hr movie the anticipated punch-line is really hard to watch. Nobody seems to have a definite answer to why this happens, other than say poop happens. Here is the FREE way I correct this problem:

Before making any changes, like cutting out unwanted sections:

Open your AVI in VirtualDub, under “File”, “File Properties”, check to see if the video and audio are the same length. If they are not the same length, then…

Under "Video" select "Frame Rate".

In "Source rate adjustment" select "Change so video and audio durations match, OK.

Under "Video" select "Direct stream copy".

Under "File" select "Save as AVI".

Save to the other hard drive.

Check your new AVI's file info and you will see that the audio and video are the same length.

Go ahead and cut the unwanted sections.

Save back to the original hard drive making sure the video "Direct stream copy is still checked", or frameserve to TMPGEnc or other.

This will probably produce an AVI with a frame rate of 29.968 or thereabouts which is still within the normal parameters of most encoding programs (TMPGEnc has no problems with it).

[suppafreak]

Try using ScenalyzerLive to capture the video. I had the same problems, when capturing using Adobe PPRO. Once I switch to ScenalyzerLive I had no more problems.

ScenalyzerLive checks the audio sync during the capture. Search for it in the Tools section.

[ima2hd]

alex1234 Are you using the MMC software with ATI to capture? If so it will not show you accurate dropped frames or show no dropped frames at all. If you are going to be capturing AVI use Virtual VCR it is free and an easy app to use; furthermore it has an option to keep audio & video in snyc. The mpeg2 captures you are doing are not as CPU intensive & therefore your vid's have audio in sync. Not sure what your source material is but AVI captures from the S-video is the only way your going to get top notch vid's then ran through an mpeg2 encoder CCE/Tmpgenc. I'll try to help further if you want to email me & btw if you do anything at all on your PC while capturing in AVI you will lose frames. I have included a screen shot I did of Battle of the Bulge captured in AVI 640x480 then ran through AVI 2 XXX CCE as my encoder 2hrs 41 min fit on a 4.3G disc Authored with tmpgenc author. As you can see the quality is excellent.

[alex1234]

... If you are going to be capturing AVI use Virtual VCR ...

I tried however, it does not capture with resolution higher than 320x240, I don't know why. When I select a higher resolution it does not complain but silently captures to the same 320x240, even the preview screen does not change.

The ATI MMC however allows me to capture to any resolution but... audio is out of sync

[ima2hd]

Alex this may help here if it doesnt let me know.

6.3 Capturing using VirtualVCR
If you own a capture card that is based on WDM (=Windows Driver Model) drivers, problems when capturing with VirtualDub occur frequently. There are several capture programs that utilize WDM though, and one of them is VirtualVCR, which has some unique features, one of them and probably one of the most important is that it is freeware.

Configuration
After starting VirtualVCR you'll first get this sparse window:


The toolbar includes the following options:

Opens the settings dialog.
Saves the current settings as the standard profile.
Opens another profile.
Saves the current settings to a new profile.
Starts the capture process.
Activates the preview.
Opens the statistics window.
Displays a list of dropped frames.
Now click on the first symbol to open the settings dialog. It is recommended to the adjust the settings in the following order:

Path and filename of the capture file.
If you check this checkbox a time stamp is automatically inserted into the filename. Recommended to prevent the overwriting of files!
Adds a compatibility index to the avi file; only needed for old applications.
If you check this box a log file is created containing the most important statistics of the process like dropped frames, etc.
With the stop option you can set conditions that tell VirtualVCR when to stop the capture process:

Here you can specify a max duration of the capture process.
Quite self explanatory. VirtualVCR automatically quits after the capture process stops.
Set a threshold for minimum free space.
Minimum free space in MB.
In order to not have to specify these settings every time you can start VirtualVCR with special parameters!
The next important tab is 'Devices':


Here we first choose our Audio and Video capture device and then hit 'Select'. Due to a bug in VirtualVCR those settings aren't taken into account immediately. Therefore we close the settings dialog box by hitting 'Ok' and then immediately reopen it again.

In Video source we specify the appropriate input (Video Tuner, Composite or S-Video).

In Device Settings we now choose 'Video Capture Pin' and hit 'Prop'. This opens the settings dialog for your capture card, which is similar as this one:


Frames per Second.
Colorspace. If YUY2 doesn't work, try other settings. This depends on the hardware you are using.
The resolution, for PAL 7** x 576, for NTSC 7** x 480. It is recommended that you choose the largest resolution.
If your card supports hardware based preview, you can now choose Video Preview Pin in the Device Settings and adjust the settings to your preference there. My card theoretically supports hardware preview, but effectively it doesn't work as expected. Anyway in this case you can always use Smart Tee Filter for the job. More on that later on.
Next tab is 'Audio':


If you also want to capture audio (who doesn't?), tick the checkbox!
In the 'Format' area you can choose Resolution, Frequency and the amount of channels.
After clicking 'Input Settings' you can choose the input type (e.g. Line-In)
Under 'TV audio' you can adjust special audio settings for direct TV capture. Some transmissions can contain more than one audio channel or special commentary for visually-disabled persons.
If you want to compress the audio while capturing you have to check 'Compress Audio' (not recommended)
Choose the audio codec if compression is switched on.
Settings for the audio codec.
In most cases you capture audio and video streams utilize different hardware (e.g. TV-card for video, sound card for audio). These cards might work with different system frequencies and therefore sync issues can arise during the capture process. VirtualVCR has a feature that almost no other capture application has: it can resample the audio stream dynamically. To do so the time difference between audio and video is calculated and then the audio is resampled to keep the whole thing synced. In the 'AV Sync'-tab you can adjust these settings:

Here you can enable/disable this function.
Here you can toggle the dynamic resampling.
If the difference between audio and video frequency is constant you should choose this option.
The relative difference between audio and video frequency.
If the offset between audio and video is constant you can sync audio and video here.
Sync the audio using the DirectShow-Interface values.
Manual syncing.
Video - Audio offset in milliseconds.
If one of the streams should 'act' as a Master Stream enable this option. (Only possible if Resample Audio (1.) is disabled).
Enable the logging of the offset values. This file can get fairly big, therefore it's only recommended for testing purposes (short clips).
Next you have to adjust the tuner settings. If you are capturing from another video source you can skip this step:

When opened the Tuner- dialog is empty, but we are going to make the TV Tuner device search for channels in a minute. First we have to set the country code and the input type though. Therefore we hit the button TV Tuner Device. The following dialog box opens:


Here you can set the country code, for germany it is 49.
The input signal of your Tv-card.
Tuner mode: TV.
PAL, NTSC or Secam.
If you are done with the settings hit 'Ok' to get back to VirtualVCR. Now hit the button 'Scan'. After the alert that the scan-process will overwrite all prior settings the following dialog box will appear:

Activating 'Aggressive Channel Scan' will result in more channels being found, including those with a weaker signal. If you want to use those channels you can decide later on, therefore I'd recommend activating the checkbox. After the scan is done a list with all channels will pop up:


I recommend that you also name the channels appropriately! To do so, just choose the channel in question and enter the name in the 'Name' field. Afterwards you have to hit 'Update' or the new name will not be saved!

This work is rather straining, but don't worry, you'll only have to do it once! After everything is done, we are going to close the dialog box by hitting 'OK' and then saving our Settings as the default ones. You can do this by hitting the button with the 'Floppy' - symbol in the main window of VirtualVCR.

VirtualVCR can already apply filters during the capture process, which is not recommended though. It is way better to capture the unfiltered movie first and then do some post-processing in VirtualDub or AviSynth. For completeness sake I'm going to explain the filters tab too:


Activate filtering during the capture process.
In this list in the beginning only filters are shown which have been installed with VirtualVCR.
To show all Direct-Show filters, you have to check this box. It will add all available filters to the list (2).
By hitting the 'ADD' button you can add a previously selected filter to the process!
This list shows all activated filters. The filters are applied in the shown order.
By hitting one of these buttons you can (re)move the filters or change their properties!
Remember to again save your settings as standard settings if you desire to do so!
Now we can first try to start the preview window. To do so we are going to hit the monitor-symbol (# 6) in the main window . If you do not see a picture now, VirtualVCR can't handle the Preview-Pin of you card. In this case Smart Tee Filter helps.

Attention! Always close the preview window before changing settings in VirtualVCR!

To activate the Preview mode go to the settings dialog again and navigate to the View tab.


Use Smart Tee Filter for Preview
The Smart Tee Filter parts the Capture-Signal into a capture-stream and a preview-stream.This should always be activated if VirtualVCR cannot handle the preview pin right or it doesn't work correctly.
Dock Capture Stats Window
As it says, this docks the capture statistics window to the main window of VirtualVCR
Show Capture Stats on Stop
...
Show Color Histogram
displays a color histogram during the capture process
Show Audio Scope
By looking at the audio scope (during capture, or testing) you can find out the fitting audio settings.
Always on Top
...
Hide Tool/Status Bar
...
After hitting 'OK' again and showing the preview you should hopefully see the picture in the appropriate resolution:

If everything worked fine it's once again time to save our settings as standard settings.

The Capture
If all settings are correct and Audio and Video sound/look ok, it's time to finally proceed to the actual capture process!

Manual Capture
With a simple click onto the capture button (# 5) VirtualVCR starts the capture process. You can always see the current status in the statistics window, which you can activate by hitting the stats button (# 7)

During capture the toolbar is reduced to these three buttons. The very left one stops the capture:


Manual capture with time limit:
If you cannot be here (or do not want to have to watch the time) you can set a specific time period after which VirtualVCR stops the process automatically. The setting can be found in the 'Stop' tab of the settings dialog.

Timer-based capture
This is not a built in function but a separate freeware program. You can find the download link at the end of this page. VirtualVCR Scheduler starts and stops the capture process at a time you specify in advance.

VirtualVCR Hotkeys
VirtualVCR can be accessed by a number of Hotkeys:
Key Function
F5 start capture process
Esc stop capture process
P toggle Preview
S toggle Stats window
F toggle fullscreen mode
H toggle tool and statusbar
T toggle 'Always on top'
C calls the settings dialog
Page Up Next higher channel
Page Down Next lower channel


Commandline parameters for VirtualVCR
You can also call and set VirtualVCR via commandline:
Parameter Function
-capture immediately start capturing after start
-channel "X" channel number
-profile "configfile" Choose another configuration than the default one. "configfile" must be with a full local path (c:\yourdir\yourconfig).
-runfor "seconds" length of the capture in seconds
-output "capturefile" name for the output file.


References:
VirtualVCR
VirtualVCR Scheduler


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[FulciLives]

I guess this is a question for LordSmurf but with ATI capture cards I thought I read once that there is a way to use an internal wire to connect the audio from the capture card to the audio card (or I guess the audio "card" built-in on the motherboard) and that using this method seems to keep A/V sync.

I never used ATI capture cards so what do I know ... LOL ... but I do remember reading another thread about this and how the person had A/V sync issues until using this "internal method".

Please note I think this was with an ATI AIW so I am not sure how those differ from the ATI TV Wonder Pro.

- John "FulciLives" Coleman

P.S.
Take a look at LordSmurf's website: DIGITAL FAQ

[ima2hd]

Dear UNDEAD OVERLORD: One would typically route their sound via the ati purple dongle; however one can bypass this sending audio directly into their sound card. I have found this to make no difference, but you can try it I doubt it will fix the sound out of sync issues. You can also try upgrading your sound card as Lordsmurf suggests, a good sound card that is one that does not take away from cpu usage. That said I have found no difference from using the on board sound vs. a dedicated sound card in regards to audio sync issues; however I think it is well worth having a separate sound card for better sound captured, more functionally, etc, etc.

[SLK001]

... If you are going to be capturing AVI use Virtual VCR ...

I tried however, it does not capture with resolution higher than 320x240, I don't know why. When I select a higher resolution it does not complain but silently captures to the same 320x240, even the preview screen does not change.

The ATI MMC however allows me to capture to any resolution but... audio is out of sync

The resolution issue is usually due to the lack of the proper WDM drivers for your card. Also, your AVI is probably NOT out of sync with your audio. On playback, the video doesn't playback in real time (but the audio does), so the audio appears to be out of sync. Try starting your video toward the end of the file, and see if the audio starts in sync, but slowly gets ahead of the video. You don't post your computer specs, so I can't tell if it is "sufficient".

VirtualVCR is a very nice program for capture. I highly recommend it.

[FulciLives]

I've tried VirtualVCR with a BT chipset capture card on two different computers now and at one point it didn't work on my "old" computer then it suddenly did start to work. Go figure but that "old" computer often went though a lot of changes and also alot of "fresh starts" (delete the HDD and re-install Windows etc.)

On my new computer (very fast with more than enough horse power for AVI capture) I cannot get VirtualVCR to keep 100% sync using the infamious "dynamic audio sync" feature (the selling point of VirtualVCR).

I do get audio sync uisng TheFlyDS or iuVCR and setting the AUDIO as the MASTER STREAM.

All I am saying is that VirtualVCR is not perfect for sync issues.

I have no idea what the issue is in regards to the limited resolution options though. That is an "odd" one since usually it happens with VirtualDub when using a WDM driver but I never heard of this limitation showing up in a capture program that worked with WDM drivers unless maybe it is because you are using a VFW driver?

- John "FulciLives" Coleman

P.S.
On my new system VirtualVCR sync stays VERY close to "on target" through-out the capture but if you read lips closely or look at things like someone knocking on a door etc. you can tell it is just barely off ... but enough to make me insane LOL

[SLK001]

I've heard reports of people not having any luck with the "dynamic resampling" of the audio using VirtualVCR. I wonder if this has something to do with the audio card/chip (maybe it not having the capability to encode at other than "standard" rates?).

If the WDM drivers are not loaded, then the program will default to the VFW drivers, which are resolution "limited". I am using the Winfast 2000XP card, which IIRC is BT based, with no issues.

If you do this enough, even non-sync issues in the original become noticeable to the practiced participator.

[reboot]

I also had issues with audio sync, using many avi capture programs. VirtualVCR did better than most, but still not perfect.
I did find out that the clock chip on my audio card is NOT perfectly where it should be, so using Line In, with the audio patch cable, resulted in out of sync. I had to manually play with the offset in Stoik video capture, and finally got something respectable, but the trial and error method just takes too long, and progressive sync error is just about impossible to fix.

[rkr1958]

Please help me to understand why if I capture to an AVI a long scene (~ 1 hour) I've got sound out of sync with the video at the end of the file?

Based on my experience using Ulead 6 to capture to AVI. The audio is captured at 32-KHz, or 32000 Hz. But due to capturing error the acutal rate is around 31995.56 Hz. But when played, the player plays the audio at 32000 Hz and thus get ahead by 4.44 Hz x 3600-seconds, or 15984 samples, which is roughly 0.5-seconds in an hour. The Goldwave timewrap function takes care of that. Also, I use Goldwave to convert the audio to 48-KHz for use with TMPGEnc DVDAuthor w/ac3 plugin which encodes the audio to ac3.

[ronnylov]

I solved my sync problems by recording with AVI_IO. But it requires vfw drivers or the wdm-vfw wrapper. But it works fine for me with the wrapper and ATI All-in-wonder Radeon.

AVI_IO drops or duplicates video frames automatically to keep the video in sync with audio.