Video is lagging behind the sound?

Hi guys,

We've just launched a new version of Silverback that addresses audio/video syncing issues. Could you give it a go and let us know if this fixes the problem for you?

I am also having a problem with lagging. My captures are about :30 to :50 minutes, and start off "on sync" but are about 2 to 3 seconds lagged by the end. It's very notable, and seems to drift without any single "event" that causes the lag. I've tried re-exporting with screensavers and other processor intensive apps off, but haven't seen a difference. Any other export settings I should try?

Hi Nick,

I'm really sorry to hear the audio is still lagging for you. Thanks for letting us know about it. Could you possibly email me a system profile report to anna@clearleft.com so we can see if we can pinpoint the problem?

To do this, click on the Apple > About This Mac > More Info > File... > Save As

Also, could I just confirm you are running the latest version of Silverback?

I've emailed the report -- thanks for the quick reply. Yes, I'm definitely running the latest version of Silverback.

Do you think system plugins could interfere with the export? For example, I run quicksilver, istats menu, a few things like that.

Thanks Nik,

I've sent the report onto the developer and have asked him whether system plugins would cause this problem, and which export setting you should try. Did you pause the video at any point during the session?

No, I did not pause the video during the session, nor did I pause the video export. There's 8 of them, and they all have the same issue; by the end of the export, it's off by several seconds. A gradual drift.

My problem is actually the reverse, the video track is longer than the audio track. I recorded 7 sessions and their exports all seems to have this issue. The audio is in sync at the beginning and then the audio slowly becomes out of sync. The last 1-2 minutes of a 30 min session have no audio at all. I used High quality and 75% reduction but tried one at 100% and Best quality and it has the same issue. I'm on a 2.33Ghz Intel Core 2 Duo MBP with 2GB of RAM.

Derek, my problem is the same: the audio slowly syncs out, and runs behind the video; at the end of the video, there is no sound. Not quite as extreme, though: a 37 minute video is off by several seconds at the end.

My current workaround solution is to import into iMovie, separate the audio track, and hand adjust it to fit the video. Extremely tedious.

The new (1.1) version of Silverback *causes* this problem for me -- I didn't have this problem in previous version of Silverback. The audio starts in sync on a pip video and then slowly goes out of sync. We never had this problem with earlier version of Silverback. How can I get the earlier version and get rid of this buggy upgrade?

Anna -- I'll send you an email and upload some raw session data for you to download.

I moved my files that were created in Silverback 1.1 (on a macbookpro) to an iMac that has Silverback 1.0.2 on it. I used Silverback 1.0.2 to export the videos-created-with-1.1 and the sync problem still exists in the exported quicktime movie.

I've opened and watched past videos both created and exported with 1.0.2 and none of them have a sync problem. Based on this it seems that videos *created* in 1.1 are the problem.

I don't have time to do the tedius manual adjustment that Nick is doing. My videos were never paused during recording. My videos created in 1.1 are all approximately 30 minutes long. Videos created/exported in 1.0.2 in the past are all between 30 and 60 minutes long (with nary a sync problem) -- I don't have any raw session data for video created/exported in 1.0.2 because we export the data and then save/backup the .mov files and clean out Silverback.

I've now exported videos created in 1.1 multiple times, in multiple quality/size configurations on the same machine we've always used for Silverback, with nothing else running, with plenty of hard drive space available (40gb), with no internet connection on, and I can't get my recent project videos to export the way they used to in 1.0.2 without audio lag.

Thanks Iwaldal, all the details you have given us are really useful. I'm passing everything onto the developer so we can get a fix out as soon as possible. We'll let you know here as soon as there's an update.

Is there a fix for this yet? This is a showstopper bug and essentially makes the application useless. We have several hours of video we need to export and deliver to clients and we are currently unable to do this.

Perhaps the previous version of the application should be make available?

when reviewing some of the recordings where the sound falls out of sync I noticed that sections of the audio have been dropped. A few words out of the subject's sentences are missing in a few places.

Is it possible to "roll-back" to an older (working) version of silverback? I purchased the product today and I'm right now in a middle of important recordings of usability tests. It's urgent!

I have the same issue. Looking at the raw VideoCapture.mov file in the project folder, it seems the problem lies there - the audio track ends before the video. So it seems it is nothing to do with the compositing of the final output where the video is overlayed on the screen activity, but the initial recording?

Further info:
I had done a number of test recordings to my local hard disk (macbook pro) and the syncing is fine the longest recording is about 17 mins.

I have since done a 59 min recording to an external hard disk (firewire 800 connection), and by 17mins into this recording the syncing is significantly out.

I was wondering whether the length of recording was an issue when it occurred to me that the external disk could be a factor?

I am having this problem too. I just updated to the most recent version a few days ago, and now the isight video and audio are out of sync (both in the exported file and the VideoCapture.mov file). In some sessions the audio and video get out of sync as early as 30 seconds in, which seems to correspond to some skipping and blockiness in the video.

I'm also using an external (USB powered) disk, which I think would be quite common practice as the last thing you want to happen during a session is to run out of space on your boot disk.

I have a whole day of user testing, 5 sessions of 30 - 40 mins each that now have this problem. I will try to fix the audio / video sync in iMovie too, as it doesn't look like installing a new version of silverback and then re-exporting will fix this (as the VideoCapture.mov file is out of sync before the export).

I can send a system profile report and raw session data if it will help.

Andy, I think you're right - This morning I've tested recording a session to internal disk, copying the session files to an external disk and running the export form there and it worked fine. Recording a session to the external disk and then exporting from there resulted in synchronisation problems.

Work around solution for me when 'in the field' I think will be to record each session to the internal disk, then copy it off to my external disk for export later. Thus I can delete sessions from my internal disk should it become short on space.

hm, I wasn't using an external drive, nor was I running lots of other apps so it's unclear where a memory problem would occur. But i'll have a play with the new version and see if the problem happens again.

Andy, as requested I've emailed you (through the clearleft website) for details of the new version. FYI The sync problems I have had were with a firewire 800 drive not USB

Thanks,
Phil.

i also sent you an email the other day and again today but haven't heard back yet

just fyi, in case it sheds more light on this problem, as I was reviewing the VideoCapture.mov file in the Silverback project folder I noticed that the sound is actually not in sync with the video there either. Parts of people's words are dropped off, the same as my exported file.

Hi,

Just in case you missed it we have released update 1.1.1 which addresses this problem.

You will be prompted to update Silverback the next time you launch.

Please let us know if you are still experiencing any problems.

Chris