Second audio track out of sync with video

[websemantic]

Hello, first post - I'm a bit lost, so thanks for any help.

I filmed a series of interviews. The audio on my camera isn't so good so I also recorded audio tracks with a microphone (using Windows Sound Recorder). I am using Windows Movie Maker (2011) to add the audio track to the video. I can't get them to sync. Even if I use Audacity to change the length of the audio so they start and finish at the same time, they drift out of sync during. From what I've read this may be due to VBR??

I used the mediaInfo tool to find that the audio (WMA) is CBR but the video (MPEG-4 MOV AVC) is VBR.

Is there anything I can do about this (convert VBR to CBR?) or would I be wasting my time and there is no way the files can be synched?

Many thanks for any advice. I've printed the media Info output for each below in case it helps:

Audio:
Format : WMA
Format version : Version 2
Codec ID : 161
Codec ID/Info : Windows Media Audio
Description of the codec : Windows Media Audio 9.2 - 96 kbps, 44 kHz, stereo 1-pass CBR
Duration : 1mn 40s
Bit rate mode : Constant
Bit rate : 96.0 Kbps
Channel(s) : 2 channels
Sampling rate : 44.1 KHz
Bit depth : 16 bits

Video:
Format : AVC
Format/Info : Advanced Video Codec
Format profile : Baseline@L4.1
Format settings, CABAC : No
Format settings, ReFrames : 1 frame
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 1mn 17s
Bit rate mode : Variable
Bit rate : 22.8 Mbps
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 29.970 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.825

[hech54]

Your duration time between the video and the audio is different to start with.

[websemantic]

Hi hech54, thanks for replying but the details above were taken from the source files before any editing or attempts to align. I am using Audacity to trim the audio and then Windows Movie Maker to align the audio with the video (starting the audio later in the video). Therefore, I am not just starting them at the same time, in which case the length would matter so I don't think that is the issue - but please correct me if I have misunderstood.

[hech54]

Hi hech54, thanks for replying but the details above were taken from the source files before any editing or attempts to align.

Yes I know....and it doesn't matter....it's best to start off with the correct/same duration first. Study the video, study the audio, then cut at least the beginning of the audio file to match where the video's audio starts.
If you can get it close....I'd try virtualdub to open the video, then open the second audio(after it's beet cut by you) then try to "skew" the audio + or - milliseconds. I would do it in Magix Movie Edit or something similar. Simply cutting and remuxing is nothing but a guessing game....and I've never used Movie Maker.

[websemantic]

Hi hech54, thanks again. Even when both video and audio are the same length and both start and finish at the same time, there are points in between when they become 'de-synchronised'. So, if I leave the audio track on the video un-muted, this audio and the separate track I am trying to overlay onto the video can start off perfectly synchronised and finish the same. However, in the middle they are out of synch. I am guessing this may be to do with the video being in a VBR format but I'm not sure. Sorry for any confusion, clearly I am guessing at things here.

[davexnet]

You may want to try AVIdemux with the AVS proxy. This allows you to use AVIsynth to serve the frames.
Try directshow/dss2, I've found that it helps with VBR video.

[websemantic]

Hi davexnet, I understood about 50% of that post I obviously have a lot to learn so thank you for giving me some starting points.

[davexnet]

NO problem. First, install Avisynth, AVIdemux and Haali Media splitter.
See this page for general info about running the proxy, it mentions a few plugins you'll need to get
(if you don't have it already). http://www.avidemux.org/admForum/viewtopic.php?id=4397

Download the proxy from here:
http://code.google.com/p/mulder/downloads/detail?name=avsproxy_gui.2010-10-01.zip&can=2&q=
and copy avsproxy_gui.exe into the AVIdemux program files folder (For example, C:\Program Files\Avidemux 2.5)

To use AVIdemux with the proxy, open the AVSproxy_gui, and add your source on the DShowSource tab.
Select "Use Haali's directshowsource2".
On the lower left, select "show details", then at the bottom left,
select the box to automatically start AVIdemux.
Select the "create proxy" button and AVIdemux will open.
On the left, choose your video and audio codec and Format.
CTRL-S to save (encode) the file.

[websemantic]

Hi davexnet, thank you again for the very detailed instructions. I'll follow them and get that all up and running. I need to ask a stupid question (my favourite kind) though. What will this do? Does it convert VBR video to CBR or is it just more powerful when it comes to synchronising video with separate audio files?

[davexnet]

Does your original video contain the camera audio and you're trying to replace it with your mic-recorded version?
For example, you could use the proxy to frameserve the file to AVIdemux
and when Avidemux opens you could point the audio to your external (mic) file.

Using DSS2 in the proxy essentially removes the vbr framerate leaving it much easier to synch in a new audio - but as I mentioned, it will need re-encoding.

Give it a go and let us know how it goes.

[poisondeathray]

the framerate is CFR

Frame rate mode : Constant
Frame rate : 29.970 fps


CFR video never causes problems, VFR video causes many problems but you don't have this.

VBR video bitrate (not frame rate) rarely causes these problems (I would say never)

VBR audio (bitrate) can cause sync issues in some circumstances, but you are using CBR audio



Variable Sample Rate can cause sync issues, and this can occur with WMA
https://forum.videohelp.com/threads/284798-%5BSOLVED!%5D-Converting-Variable-Sample-Rat...547&viewfull=1

[websemantic]

poisondeathray, that's exactly what I was looking for - I wasn't sure about the impact that varying bit and frame rates have on the output. I'll report back how I get on with the solution in that thread in case it helps someone else. Thanks you to all for your answers, I have learned plenty in a short space of time (especially that I have a lot to learn). Cheers!

[websemantic]

davexnet, sorry, I didn't see your post. Thanks, that's clearer, I'll report back - probably towards the end of the week as I'm meant to have this fixed and presented for Thursday. Can't beat last minute problems

[davexnet]

OK. If all else fails, you could always (assuming it's not confidential) post the file here and let somebody
else look at it.

[websemantic]

I'd just like to say that my problem is fixed so a big thanks to everyone for your help. The solution came from the link provided: https://forum.videohelp.com/threads/284798-%5BSOLVED!%5D-Converting-Variable-Sample-Rat...547&viewfull=1 and specifically:

1) add the fukking wma to the playlist of WinAmp;

2) goto Icon Menu, Options, Preferences, Plug-ins, Output,
NullSoft Disk Writer; configure, OK, close;

3) Click the Play button;

For those that it isn't obvious for (like me), tick the "Convert to format" checkbox in the configure dialogue.

In case it helps others, a quick, and hopefully clearer, restate of my problem:

I shot an interview on video. I also recorded the interview on microphone (using Windows sound recorder, stupid, should have used Audacity). I wanted to mute the video sound and overlay the audio from the microphone. As I had used Sound Recorder, the audio files were in WMA format which is variable bit rate. Therefore, when I overlayed the new audio onto the video, it would drift in and out of synch. Using the coversion above, they now are in synch.

Thanks again!