help with re-sync'ing Audio please

[snadge]

I have an MPEG-4 XVID movie file (AVI) with Audio (MP3) thats out-of-sync

can anyone guide me to fixing this?

much appreciated

thanks

[poisondeathray]

does it come early or late? and is the delay constant? If it's a constant delay, find the audio shift value in your media player (e.g. +/- keys usually shift the audio) , and use avidemux to enter that audio shift delay

is it in sync and then gets progressively worse? If it's progressively worsening, it means the audio & video lengths don't match. You could either shrink/expand the audio or video (change fps) to match

are there glitches? glitches can cause desync errors. These are tough, you often have to cut the video into segments and process it manually by section

[snadge]

thanks...

the audio starts in sync THEN falls out of sync maybe by about 50ms at end but cant be sure how much....

how could I expand the audio?


thanks

[poisondeathray]

the audio starts in sync THEN falls out of sync maybe by about 50ms at end but cant be sure how much....

how could I expand the audio?

audacity

It may help to find the lengths of audio & video first, then calculate the ratio to adjust the audio by. You could look at mediainfo (view=>text) , but it's not always accurate

[snadge]

thanks - i will try

this is too play on TV so may not play 'odd' frame-rate (DivX 7 codec)
so how do I remove audio then tmux it back in when done?

Format : AVI
Format/Info : Audio Video Interleave
File size : 1.35 GiB
Duration : 1h 57mn
Overall bit rate : 1646 Kbps
Writing application : VirtualDubMod 1.5.4.1 (build 2178/release)
Writing library : VirtualDub build 30091/release

Video
Format : MPEG-4 Visual
Format profile : Streaming Video@L1
Format settings, BVOP : Yes
Format settings, QPel : No
Format settings, GMC : No warppoints
Format settings, Matrix : Default
Muxing mode : Packet Bitstream
Codec ID : XVID
Codec ID/Hint : XviD
Duration : 1h 57mn
Bit rate : 1540 Kbps
Width : 624 pixels
Height : 336 pixels
Display aspect ratio : 1.857
Frame rate : 25.000 fps
Resolution : 8 bits
Colorimetry : 4:2:0
Scan type : Progressive
Bits/(Pixel*Frame) : 0.294
Stream size : 1.26 GiB (94%)
Writing library : XviD 50

Audio
Format : MPEG Audio
Codec ID : 55
Codec ID/Hint : MP3
Duration : 1h 57mn
Bit rate : 96.0 Kbps
Channel(s) : 2 channels
Sampling rate : 22.05 KHz
Stream size : 80.4 MiB (6%)
Alignment : Split accross interleaves
Interleave, duration : 40 ms (1.00 video frame)
Interleave, preload duration : 500 ms

[snadge]

just dont know what im doing here.... audacity seems to be for the audio? so i need to demux , stretch and remux? hmmm i dunno how AND could be wasting my time if i remux and its still off....

there has to be a simpler method for this common problem? surely?

[poisondeathray]

you can use audio=>save in avidemux , fix the audio, then remux either with avidemux or avimux-gui .

If you don't know the exact ratio or numbers, it might be easier to adjust the frame rate of the video by small increments, using avifrate , or vdub .

Here is a guide (scroll down)
http://www.gromkov.com/faq/faq2004-0064.html

[snadge]

im just worried that odd frame-rates wont work on my TV mediaplayer which uses DivX 7 codec and plays upto 1080p 20Mbps

ive got the audio extracted... is there anyway i can find out the actualy delay at the end? so i know how much to increase it by in audacity?

thanks BTW

[poisondeathray]

From what you 've told me, there is no delay at the end. It begins in sync, then gets out of sync. This suggests a mismatch in a/v length

If your hardware doesn't play "off" video frame rates , the only way to do it is to fix the audio instead of the video

I don't know of any way except by trial and error. Sometimes you can get the ratio from mediainfo (the duration of the video & audio) , but in your file, it is the same. You could use the avifrate with some trial and error , to find the ratio, then use that in audacity. Avifrate is much faster to use, than resampling & re-encoding audio many times for trial and error

[snadge]

i meant the delay between the audio and video near end so I know how many MS to adjust the length by in audacity... I have the MP3 loaded in AUdacity... is there anyway of playing the full movie fle and finding out the delay near end or is it just GUESS work.... remux then see if it worked?

[snadge]

so how do you 'stretch' it by say 50ms or 100ms in AUDACITY...? i cant find any options?

[snadge]

also that guide you linked to is outdated and links to programs no longer work... (AVI FPS CHANGER)

[poisondeathray]

You wouldn't change it by 50ms , you would change it by the fraction. So you need to know the durations in ms. e.g. If a video was 60s and audio was 59s , you would stretch the audio by 60/59

Click the hotlink for avifrate
https://www.videohelp.com/tools/AVIFrate

EDIT: The links for that guide are working for me. That program is slightly different than the one at videohelp, but the idea is the same

frateadj100.zip

[redwudz]

You can try this in Audacity. Using the 'Change Tempo' effect, click on the Length (Seconds) 'to' box and enter the desired length. Save out in a compatible format for your audio. Add this back in with your video. I use VirtualDub for this and set both video and audio to 'Direct stream copy', and disable/delete the old audio, then save it all with a new filename if you don't want to overwrite the existing file. This will 'mux' your new audio file with your video file. Only takes a short time.

The hard part is determining the correct length of the audio file to sync with the video file. If the video file is corrupted, then it gets much more complicated as you may have to chop up the video and treat each part separately, then rejoin.

[lordsmurf]

You usually can't fix this. It's not a simple issues of stretching audio.