The Song Fight Bulletin Board

Today I recorded a video of myself playing piano and singing. It didn't come out very well, so I tried again. After several of these attempts, the problem remained unsolved, so I went ahead and uploaded the video to Youtube, hoping people on the web can help.



From the description:

There's some weird audio glitches in here. Anyone know what's causing them?

The webcam is a Logitech C310, and I used the Logitech recording software. It's set to pull audio input directly from my Lexicon Lambda, which is that box you see on the left hand side of the screen. The piano and microphone both line directly into that. They're also both set very low, so as not to clip the audio device or the software.

I also don't get why it's so badly out of sync - it was fine before uploading.

I will just take a stab at it being a cable issue. As far as out of sync after uploading it, not sure. But maybe you can ask Justin Timberlake to help remedy that.

....see that Jon? What I did there?

What audio and video formats are you recording in? If you're saving one or both to a highly compressed format in real time, that can lead to glitches and desync. I always record audio as WAV and video in some lossless or near-lossless format that gives great big files with high quality - Huffyuv is an old reliable.

What audio and video formats are you uploading to youtube in? VBR in audio can cause desync problems when youtube recodes it. If you're using an unusual framerate in the video, that might cause problems too. For youtube, I find 12fps adequate for most purposes.

Kapitano wrote:What audio and video formats are you recording in? If you're saving one or both to a highly compressed format in real time, that can lead to glitches and desync. I always record audio as WAV and video in some lossless or near-lossless format that gives great big files with high quality - Huffyuv is an old reliable.

What audio and video formats are you uploading to youtube in? VBR in audio can cause desync problems when youtube recodes it. If you're using an unusual framerate in the video, that might cause problems too. For youtube, I find 12fps adequate for most purposes.

The software isn't letting me choose which format to record in, so I assume it's picking something disadvantageous. I think I need to use a different software.

There's an amazing amount of software which won't let you do basic configuring - and a lot of it's expensive.

I recommend VirtualDub (http://www.virtualdub.org/) if you're using Windows. It's free, flexible, and outperforms most of the payware.

Yes, some friends on Google+ already recommended VirtualDub, so I went and got it.

Now my problem is that it doesn't appear to "see" my webcam.

Generic wrote:Now my problem is that it doesn't appear to "see" my webcam.

You probably didn't get the virtualDub with the i-bawl upgrade.


.......i-can't turn it off. sigh

So I got VirtualDub to work with my peripherals, and to capture into raw AVI with the audio encoded as PCM Windows Wav format. This is what came out. For the less astute, the video and audio playback both accelerate as the video goes on. If it were a problem with the wav bitrate, the speed would be off, but constant throughout the video, right? I'm at a loss here.

Accelerando!

How utterly bizarre.

Just to be clear: The accelerating effect is the result of recoding the Raw/WAV original into Non-raw/MP3? I mean it's not there in the uncompressed recording? I once had speed problems from a bad mp3 codec, but nothing nearly as bad as this. You're not using weird settings? You're encoding to CBR? Oddly, that particular problem stopped when I switched to stereo recording - you seem to be in mono here. What audio/video interleve settings do you have? I always set the interleave frequency to 10ms.

It *is* possible to have A/V shifted out of sync, *and* drift, *and* the speed to be off by a constant amount, all in the same file, in every permutation - but all these are pretty unusual nowadays. You say you're capturing raw video - if it really is raw, that takes up a *very* large amount of disk space, which on a fragmented drive might cause problems. Try Huffyuv or an MJPEG codec. But I can't see drive speed access problems causing what we see here.

If the effect *is* there when you play back the raw original, then it looks like the capture process is progressively dropping more and more frames. Were other processes running in the background? Could be a virus? VirtualDub tells you how many frames are dropped or inserted in the information panel - try filming an empty room for 5 minutes and watch the figures. In VirtualDub's playback mode (but not while playing back) check the framerate - is it what you set in capture mode?

The picture quality looks okay, but there are some extremely crappy webcams out there which can't even manage 12fps. Could you try a different cam? Finally, what's your frame size and aspect ratio? I suggest keeping to 640x480.

Kapitano wrote: If the effect *is* there when you play back the raw original, then it looks like the capture process is progressively dropping more and more frames. Were other processes running in the background? Could be a virus? VirtualDub tells you how many frames are dropped or inserted in the information panel - try filming an empty room for 5 minutes and watch the figures. In VirtualDub's playback mode (but not while playing back) check the framerate - is it what you set in capture mode?

The picture quality looks okay, but there are some extremely crappy webcams out there which can't even manage 12fps. Could you try a different cam? Finally, what's your frame size and aspect ratio? I suggest keeping to 640x480.

The acceleration is present in the raw original. VirtualDub didn't report any dropped frames. I'll try lowering the aspect ratio to see if that helps - right now it's recording in 720p. However, it should be noted that my goal here is to actually record and upload in HD.

Okay, I've been working with video for over a decade, and nothing like your acceleration problem has happened to me, and I don't recall reading about it happening to anyone else. That said, here's how I would investigate.

The problem could be in the webcam (unlikely), the codecs (possibly), the recording software (possibly) or the playback software (unlikely - given that you get the effect in different playback software, namely a browser pointing to youtube). So I'd try different recording software and different codecs - not to find an alternative recording system yet, but simply to find where the problem is.

There's plenty of low-cpu, free, trial or watermarked codecs out there - the watermark doesn't matter right now because it's just for testing. I use the PicVideo MJPEG.

http://www.softpedia.com/get/Multimedia ... odec.shtml
http://www.free-codecs.com/motion_jpeg_ ... wnload.htm
http://mjpeg-codec.fyxm.net/

Get some free video recording software.

http://camstudio.org/ (I occasionally use this one)
http://www.videomonitor.biz/

Record yourself on video, clapping for about a minute. Use the same framerate and resolution for each. Do this once for each codec, for each recorder - so 3 codecs with 2 recorders gives 6 videos. Make sure the filenames clearly show which was recorded with which system. Clapping is better than talking or music, because the exact nature of the sync problems is more easily identified.

Play it back in VirtualDub and another media player (I suggest Media Player Classic - http://mpc-hc.sourceforge.net/). If one has the problem and the other doesn't, then the problem is a codec of that works with some software but not others - a common problem.

What exactly is the video doing? Is the sound out of sync by a constant amount? Is it drifting? Is it speeding up? Or some combination of these? If it's just out of sync you can correct that easily with virtualdub. Constant desync is very common, and you'll need to correct it before you can accurately judge whether there's drift too. If it's just drifting, you've got an audio which disagrees with your video codec about how long a second lasts (fun fact: there are actually two very slightly different commonly used definitions in different mp3 codecs).

Obviously if all the codecs give the same problem, it's not a codec problem at all, so it's either your recording software, the computer hardware, or the operating system. If all the codecs and all the recording programs give the same problem...then assuming you don't have an ancient computer or an OS a decade out of date, I'm truly stumped.

Sorry I can't offer anything more direct, but I've found through hard experience that you can't beat running lots of boring tests.

Either that or reinstall absolutely everything from the OS up. Occasionally I've had to do that.

I never did figure out what the problem was here, but I reformatted the hard drive on that system for unrelated reasons, and put a new OS on it. Same software, same webcam, same song, but this time it came out nearly flawless.

Very nice Jon, I am jealous of your vocal range.