Digital Recorder and Video Sync

Jim Boda · May 15th, 2008, 08:59 AM

Quote:

Originally Posted by Steve House

...In one clip, with KT Tunstall singing "Suddenly I See" while sitting on a tree branch, she's definitely out of sync by several frames - totally unoticable on a regular TV but glaringly obvious on the big screen projection set.

I see out of sync stuff on TV all the time. There really is no excuse for it. As an editor, I can expand the timeline and determine exactly how far the waveforms are off in relation to the reference audio. I'm not looking at the monitor...I'm looking at the magnified waveforms.

Interesting enough, some camera's are actually slightly out of A/V sync.

Abe Dolinger · May 16th, 2008, 09:00 AM

For what it's worth - I used the Sony D50 recently as a "room" recorder at a music event where primary audio was going to a Fostex PD606. The 606 has an internal TC generator; the D50 does not. They stayed in sync with each other over a take of about 45 minutes.

Now in a few days I get to find out whether they stayed in sync with the non-TC cameras we shot on . . heheh, fun.

Nate Haustein · May 16th, 2008, 10:01 AM

In a two hour show, my iRivers drift maybe 5-10 frames at the end. Fixable, but annoying. One thing I saw however, was an option to sync audio to 29.97 NTSC in Apple's Soundtrack Pro 2. I'd sure like to try this, but soundtrack never wants to play with me; it's easily the buggiest program in FCS2 and crashes repeatedly. Has anyone used this feature before, and would it solve some of the problems being described here?

Kenneth Medin · May 17th, 2008, 02:56 PM

I use a Zoom H2 all the time for my videos and it is about 0.3 sec too fast over the hour. I use Avisynth for most editing and it's very simple to correct the drift with these two lines in the script:

ResampleAudio(47996)
AssumeSampleRate(48000)

All I have to do is trim the H2 WAV files to match the camera audio startpoint and then run this script:

directshowsource("SANY3406.MP4")
Tweak(sat=0.8, Hue=0)
video=last
lf_rf=wavsource("ljud\SR002R.wav")
c_lfe=blankclip(lf_rf)
lb_rb=wavsource("ljud\SR002F.wav")
sound=MergeChannels(lf_rf,c_lfe,lb_rb)
AudioDub(video,sound)
ResampleAudio(47996)
AssumeSampleRate(48000)

Here all four mic capsules are used to get a nice 6 channel WAV that later can be fed into an AC3 encoder to get surround sound. Just note that If the video is really long you may get past the 2 GB WAV file limit.

Also there is no need to worry about pitch after the resampling. At 440 Hz you will get one beat every 30 sec. if you (for whatever reason) mix the original with the resampled WAV. That's not audable at all and much less than any piano tuner can achieve.

Once you learn to stay away from the digital recording level and just keep the H2 at medium senitivity it's a great recorder. Even works handheld if you can keep your fingers absolutely still.

Luca Furgiuele · May 19th, 2008, 08:12 AM

I was giving serious thought to getting the H4 truthfully. it's the only pocket sized recorder with XLR in's which is what i want. where is this link that talks about the zoom's anyway?

May 16th, 2008, 09:00 AM	#17
Abe Dolinger Regular Crew Join Date: Apr 2006 Location: Brooklyn, NY Posts: 111	For what it's worth - I used the Sony D50 recently as a "room" recorder at a music event where primary audio was going to a Fostex PD606. The 606 has an internal TC generator; the D50 does not. They stayed in sync with each other over a take of about 45 minutes. Now in a few days I get to find out whether they stayed in sync with the non-TC cameras we shot on . . heheh, fun.

May 16th, 2008, 10:01 AM	#18
Nate Haustein Trustee Join Date: May 2007 Location: Minneapolis, MN Posts: 1,313	In a two hour show, my iRivers drift maybe 5-10 frames at the end. Fixable, but annoying. One thing I saw however, was an option to sync audio to 29.97 NTSC in Apple's Soundtrack Pro 2. I'd sure like to try this, but soundtrack never wants to play with me; it's easily the buggiest program in FCS2 and crashes repeatedly. Has anyone used this feature before, and would it solve some of the problems being described here?

May 17th, 2008, 02:56 PM	#19
Kenneth Medin New Boot Join Date: Nov 2007 Location: Gothenburg Sweden Posts: 14	I use a Zoom H2 all the time for my videos and it is about 0.3 sec too fast over the hour. I use Avisynth for most editing and it's very simple to correct the drift with these two lines in the script: ResampleAudio(47996) AssumeSampleRate(48000) All I have to do is trim the H2 WAV files to match the camera audio startpoint and then run this script: directshowsource("SANY3406.MP4") Tweak(sat=0.8, Hue=0) video=last lf_rf=wavsource("ljud\SR002R.wav") c_lfe=blankclip(lf_rf) lb_rb=wavsource("ljud\SR002F.wav") sound=MergeChannels(lf_rf,c_lfe,lb_rb) AudioDub(video,sound) ResampleAudio(47996) AssumeSampleRate(48000) Here all four mic capsules are used to get a nice 6 channel WAV that later can be fed into an AC3 encoder to get surround sound. Just note that If the video is really long you may get past the 2 GB WAV file limit. Also there is no need to worry about pitch after the resampling. At 440 Hz you will get one beat every 30 sec. if you (for whatever reason) mix the original with the resampled WAV. That's not audable at all and much less than any piano tuner can achieve. Once you learn to stay away from the digital recording level and just keep the H2 at medium senitivity it's a great recorder. Even works handheld if you can keep your fingers absolutely still.

May 19th, 2008, 08:12 AM	#20
Luca Furgiuele Regular Crew Join Date: Aug 2007 Location: Canada Posts: 26	I was giving serious thought to getting the H4 truthfully. it's the only pocket sized recorder with XLR in's which is what i want. where is this link that talks about the zoom's anyway?