Advice on Codec and more perhaps...

[levisx4]

Canon Vixia HFS30, Audio recorded on handheld recorder -> AVCHD transfered and converted to MP4 in VSX4 -> Audio Split from Video, saved as WAV, removed from timeline -> Saved WAV synced in Audacity with external audio, external audio saved as wav, and inserted into timeline -> Procedure repeated for the other clips -> project rendered as MP4 HD.

Problem:

- When played in project window, audio is well synced with video
- When played in WMP 12, audio is out of sync
- When played in VLC, RealPlayer, and QuickTime, sync is as good as in VSX4

Is this a codec problem. When I uploaded the video to Youtube, the stream was also a little bit out of sync but not as bad as in WMP 12. Google tech support claims that my audio time stamp is not the same as video time stamp, and that that is the reason for out of sync. Well, why is it then so well synched in 3 media players?

Please help me sort this one out. Thank you.

[lata]

Hi

My first thoughts are that you are doing a lot of converting/rendering, splitting audio, then using an audio editor, before re-constructing the video.

Why don't you edit the original video AVCHD without converting to Mpg4 or splitting audio?
Add the external audio file to the timeline and sync with the video
At least the video audio stream wont go out of sync.

What are the properties of the original video file?
What are the properties of the new Wav file?
What are the properties of the external audio file?

Are you using similar audio compression settings for the new file as used by the original video file?

[levisx4]

Thanks for your reply. I don't have the files with me so I can't give you all the details. Here are a few quick facts:

- The reason I didn't edit the original AVCHD files in VS is that it would crash as soon I split the audio and imported the external audio. Corel's tech support best answer (after examining the two dump files I had sent them) was that something was wrong with my editing!? All I did was open the AVCHD clip 1-2 minutes in length, split audio and attempt the insertion of the external audio into the timeline. So much for my reliance on Corel's tech support.
- The sampling and bit rates of the external audio and the one from video were the same 16/44, as was the exported wav file from Audacity, after synchronizing the two audio files.
- There were no synchronization issues during neither the editing, nor the renedering. There were approximately 20 short clips 1-2 minute each, so audio lag wasn't noticable.
- The rendered video was in mp4 HD, about 25 minutes in length, and the file size is ~ 2.5 GB.
- This file played with no synchronization problems in VS project window, VLC Player, RealPlayer, and in QuickTime. It was only in Windows Media PLayer 12, where the sound was lagging behind the video. That is why I don't quite see the relevance of your questions about the details of the files.

Thanks again.

Hi

My first thoughts are that you are doing a lot of converting/rendering, splitting audio, then using an audio editor, before re-constructing the video.

Why don't you edit the original video AVCHD without converting to Mpg4 or splitting audio?
Add the external audio file to the timeline and sync with the video
At least the video audio stream wont go out of sync.

What are the properties of the original video file?
What are the properties of the new Wav file?
What are the properties of the external audio file?

Are you using similar audio compression settings for the new file as used by the original video file?

[lata]

Hi

Are you sure the original Avchd uses 16/44, I assume you mean 16bit 44.100hz, i would have thought HD used 48,000khz

Anyway, do not split audio

Try this
Options one
Add the Avchd to the timeline
Add the other audio file to the voice timeline, sync with the top track, or am i missing something here....

Share Create Video File--choose your template, if Same as First Video Clip is available use that...
For all renders, de-select Smart Render, then "save"

Option two.
as your workflow, but deselect Smart Render

[levisx4]

Thanks again for your reply, however, please note that I am not really looking for instructions on what to do, but more for an explanation, an answer to the question:

Why does my rendered video play with perfectly synchronized video and audio - in my VSX4 Project Window, in VLC Player, RealPlayer, and in QuickTime; only in Windows Media Player 12 Audio is not synchronized with Video. I think it has to do with the Codecs associated with these players, but would like more explanation. For example, which MP4 Codec does Corel VSX4 use in rendering MP4 videos?

Hi

Are you sure the original Avchd uses 16/44, I assume you mean 16bit 44.100hz, i would have thought HD used 48,000khz

Anyway, do not split audio

Try this
Options one
Add the Avchd to the timeline
Add the other audio file to the voice timeline, sync with the top track, or am i missing something here....

Share Create Video File--choose your template, if Same as First Video Clip is available use that...
For all renders, de-select Smart Render, then "save"

Option two.
as your workflow, but deselect Smart Render

[DVDDoug]

Canon Vixia HFS30, Audio recorded on handheld recorder -> AVCHD transfered and converted to MP4 in VSX4 -> Audio Split from Video, saved as WAV, removed from timeline -> Saved WAV synced in Audacity with external audio, external audio saved as wav, and inserted into timeline -> Procedure repeated for the other clips -> project rendered as MP4 HD

Did you render to MP4 before extracting the audio? If not, try that. If the audio goes out-of-sync simply from converting to MP4, or if that doesn't solve the problem, try using SUPER (FREE!!!) to make the converseion. Super can also be used to extract the audio (from the AVCHD or MP4) to a WAV file. If you download SUPER, follow the links and make sure you are downloading SUPER setup.exe... Don't be fooled by the ads on their confusing website.

Google tech support claims that my audio time stamp is not the same as video time stamp, and that that is the reason for out of sync.

That could be true, or there can sometimes be extra-repeated video-frames. There seems to be several different causes (and solutions) to this problem. Often there are problems or corruption in the original file that don't show-up when the file is played, but cause trouble when the file is transcoded or re-rendered. The time-stamps are probably correct in the newly renderd file, but there were problems during the transcoding process. Another AVCHD file from diferent camera might work fine...

The more-advanced, more-compressed, formats are more-prone to A/V sync errors (and other weird problems) than less-compressed formats such as DV, or MPEG-2. Although, my signature below was inspired by problems with MPEG-2.

[lata]

Hi

Sorry but i use Windows XP and do not have the same version of WM Player as you so cannot comment on its performance. If you feel it is an issue purely with WMV Player then i assume you have updated the software to the latest version

MPG4 from Video Studio

there are several options to select when choosing the Mpeg4 template, video studio gives some default options, but using the Custom option will allow you to manage the settings

Share Create Video File
Custom
Mpeg4 types
Options
Compression tab--Video Types and Data Rates
General tab for frame sizes and Rates

You of course should be using settings that reflect the original video files properties.

Last word regarding Smart Render....some users have cured audio problems by deselecting this option.

[skier-hughes]

The clock cycles for video and audio are different, once you split them you run the risk of them going out of sync the moment you make any change to either.
It sounds like WMP is least forgiving of all the players on your differnces, maybe it is trying to play it most accurately, wherea the other players are more forgiving and not playing it so accurately.

[teknisyan]

Remove the first part, since I saw that there are a number or response already.

Regarding the crashing of your VS X4 when working with the original AVCHD without any conversion, have you updated your VideoStudio X4? You can download the update at http://www.corel.com/corel/pages/index. ... id=1100002

[levisx4]

I have the latest update for VSX4, as confirmed by Corel tech support.

Remove the first part, since I saw that there are a number or response already.

Regarding the crashing of your VS X4 when working with the original AVCHD without any conversion, have you updated your VideoStudio X4? You can download the update at http://www.corel.com/corel/pages/index. ... id=1100002

[levisx4]

Did you render to MP4 before extracting the audio? If not, try that. If the audio goes out-of-sync simply from converting to MP4, or if that doesn't solve the problem, try using SUPER (FREE!!!) to make the converseion. Super can also be used to extract the audio (from the AVCHD or MP4) to a WAV file. If you download SUPER, follow the links and make sure you are downloading SUPER setup.exe... Don't be fooled by the ads on their confusing website.

I did render to mp4 before extracting the audio. The audio did not go out of sync during editing, or rendering. I have played every rendered clip as well as the entire 25 min mp4 file in the project window - everything was in sync, beginning to end, as was when I played it VLC, RealPlayer and QuickTime. Only when I played it in WMP 12, the audio was out of sync, and not consistently, just in few segments.

Google tech support claims that my audio time stamp is not the same as video time stamp, and that that is the reason for out of sync.

That could be true, or there can sometimes be extra-repeated video-frames. There seems to be several different causes (and solutions) to this problem. Often there are problems or corruption in the original file that don't show-up when the file is played, but cause trouble when the file is transcoded or re-rendered. The time-stamps are probably correct in the newly renderd file, but there were problems during the transcoding process. Another AVCHD file from diferent camera might work fine...

OK, that's plausible. But how can I check for errors? How did the YT guys determine the difference in timestamps? They didn't answer when I asked them what tool did they use to find out. Currently, my only available tool is visual inspection. Can you recommend a better alternative? Many thanks!

[skier-hughes]

The audio and video time stamps are part of the meta data, you need an app that reads this.

Here is further info
http://en.wikipedia.org/wiki/Presentation_time_stamp
Mostof this isn't relevant, but some will help you understand.
http://en.wikipedia.org/wiki/Audio_to_v ... ronization

This gives some good info and clock sampling and the way it differs from camcorders to pc's etc
http://www.inventa.com.au/Audio-Video%2 ... apture.htm

[levisx4]

Thanks for the links, I saw wiki articles before, the last looks one good as far as relevant detail.

I am still looking for a tool that will allow me to inspect my rendered mp4, and reveal possible audio-video sync problems. I know about Womble's GOP Fixer, but it doesn't seem to work on mp4. Do you know of any such tool? Many thanks.

The audio and video time stamps are part of the meta data, you need an app that reads this.

Here is further info
http://en.wikipedia.org/wiki/Presentation_time_stamp
Mostof this isn't relevant, but some will help you understand.
http://en.wikipedia.org/wiki/Audio_to_v ... ronization

This gives some good info and clock sampling and the way it differs from camcorders to pc's etc
http://www.inventa.com.au/Audio-Video%2 ... apture.htm

[skier-hughes]

I've read all the conversions done, in and out of audacity you've done, but is any editing done, so after inserting your synced wav file from audacity, do you then cut pieces out or are you using the whole piece as one item?
I don't use VS as my main editing tool, I use grass valley edius, trifle more expensive and to retain sync I'd bring in my external audio and do the syncing in the video editing software.
Then any editing done retains the clock cycles of the video.

[levisx4]

I brought the synced wav file that was exported from Audacity, and inserted it into the voice track in VS, at time 0. At the other end, I trimmed both video and audio, such that video and audio were the same length as measured by hh:mm:ss:ff. Then I re-rendered this mini-project as new mp4. "Mini", because, these are 1-2 minute clips. After rendering, I checked each one of them in project window, in VLC, RP, QT, and WMP. Everythning was in sync in all of them. Then, I assembled these rendered clips in the timeline, added some background music, and rendered the whole 25 min project as mp4. That rendered file was in sync everywhere except in WMP. Further twist was that when uploaded to YT, there was some async, not as bad as in WMP, and not linear, just in few segments. And again, YT tech support blamed it on different time-stamps in audio and video, something I cannot check for myself with the available tools, which is why I am looking for some.

I've read all the conversions done, in and out of audacity you've done, but is any editing done, so after inserting your synced wav file from audacity, do you then cut pieces out or are you using the whole piece as one item?
I don't use VS as my main editing tool, I use grass valley edius, trifle more expensive and to retain sync I'd bring in my external audio and do the syncing in the video editing software.
Then any editing done retains the clock cycles of the video.