audio/video sync issue

[Hutch TV]

I am editing an Orchestral concert and the audio was recorded via a professional sound person.

The audio they supplied sounds amazing but slips out of sync along the timeline. By the time we get to an hour in, its about 20 frames out (late).

I was thinking it was maybe a SAMPLING RATE or QUANTIAZATION Bite RATE setting conflict.

My project settings in Edius are set to a Sampling rate of 48Hz and QUANTIAZATION bit rate is 16.

The audio person supplied me 4 different versions of the same audio mix ranging from 48HZ/16 Quan to 48Hz/24 QUAN and also 44.1/16 and 44.1/24 version.

BUT THEY ALL SLIP OUT OF SYNC!

Maybe I will change my QUANTIAZATION bit rate in Edius to 24 and see what happens.

Going nuts here!

[Jerry]

Is it a .wav file? Do you know if it was recorded onto a machine with timecode?

[GrassValley_BH]

Improper quantization (bit depth) will cause garbaged audio.

It sounds like the sampling rate of the audio was ever-so-slightly-off, like back in the Canon DV days.

Does the total time length of the audio match the length of the video clip?

[Ron Evans]

I always have to re sync my video to audio recorders like my Zoom R16 or even when I get a file from the audio guys. Unless the audio recorder and video recorder are genlocked they will not stay in sync too long. I take a guide wav file from the video edit exported from Edius. Place in a track in Vegas then sync with the audio files from the recorders. Set the start sync then start by going to the end and stretch or compress the file to fit. If lip sync is really important I may re sync every 20 mins or so. For concert I re sync by act. Then export the synced file as a wav file and bring back into Edius. I think Audition may be able to do the same though not sure. This is not always clock drift but a difference between the record clock and the playback clock.

Ron Evans

[AJL14]

Brandon has hinted upon a fix that has worked for me. Do a real quick piece of math - for video is recorded at 29.97 and not 30. That measures .03fps - or 1.8 frames per minute slower than something recorded at 30fps (real-time) - or 108 frames (3 1/2 seconds per hour) slower. Measure your video and audio tracks and see if this math figures in. Then you can try altering the sound in "speed control" by a fraction so the lengths of the total tracks are the same. You won't hear a difference in pitch for a very slight speed change. I can't guarantee it will work for you, but it has cured the same problem more than once for me.
Alan

[Hutch TV]

Audio sync issue

Thanks everyone,

I might just try that Ajl14, otherwise because its an Orchestral piece I might just nudge it back into sync every 5 mins or so, where there is a pause that is.

Its not being broadcasted its for archival purposes, having said that I dont need a situation where someone goes "Who edited this for its slightly out of sync"!

thanks again.


Martin
Australia

[Harro]

As you are in Australia, I assume that you took the video at 25 fps. 20 frames is only 0.8 seconds out after an hour, so why not simply adjust the video length (speed) to match that of the audio length. The adjustment should be so slight that no-one will ever notice it.

[Vaughan Wood]

BUT THEY ALL SLIP OUT OF SYNC!

Hi Martin,


I'm very interested to know what it was recorded on?

I used a Zoom H2 to record many concerts for years without a problem, then bought a Tascam DR40 last year with awful results. The 1st concert I did just did not sync, the Tascam drifted everywhere. (48HZ/16)

Sent it back, bought a Zoom H4n, sync perfect again.

Never seen any other comments about poor sync from Tascams though.

Life is stranger than fiction!!

Cheers,

Vaughan

[NakedEye]

The only way to get perfect sync is if sources are locked to a time clock. The crystals oscillate at slightly different frequencies. Best bet is to resync regularly - maybe every 20mins as suggested earlier. Edius allows some fine tuning when slipping audio. Timeremap also is a great tool here.
There is nothing wrong with the Tascam recorders.

[PaulTV]

It's true - that's why equipment was always fitted with Genlock - two oscillators will never run truly in sync without one being referenced to the other.

Best route is as suggested, adjust your vision clip length to match your audio and render an HQ file - you'll never see it ( set field option to none in speed change dialogue)

This will leave the audio pitch untouched - even very good software will leave bad errors in complex sounds such as classical music when re pitching - and any musician will tell you it's wrong.

Paul

[dpalomaki]

Agree. Concert video is generally boring unless there are lots of cuts to different views of the performers. Plenty of opportunuity to add/delete a video frame at cut points to keep sync with the sound. Musicians will see if the fingering is not in sync with the audio, and sound leading video is unnatural.

[Ron Evans]

The issue with recorder sync, as mentioned , is the clock that the recording was made with is not the same as the clock for the video. So when the audio is played with video it is not at the pitch it was recorded at. To get the pitch correct it will have to be corrected to the video clock because that is how it will be played back, not from the audio recorder that recorded it in the first place. Just brought into the video it will be off pitch when played back with the video. Stretch or Squeeze the track will bring it back to correct pitch in sync with the video. Just cutting pieces will leave it off pitch. Visual sync for musicians and dancers is very critical as well as for closeups of actors for lip sync. Edius cannot move/stretch/squeeze audio as easily as an audio editing program. Over 3 or 4 mins my Zoom H4 or R16 will hold sync close enough , but for an hour they are both off sometimes by as much as a frame. Not much you may say but enough for an echo and for lip sync or dance enough to be annoying if mixed with other audio. That is why I use Vegas to resync as it can move the audio by clock sync not video clock as well as stretch and squeeze. Of course I never thought to state the obvious that most audio recording maybe 44.1k not 48k too.

Ron Evans

[GrassValley_BH]

Word clock is the audio analogue of video's of Tri-level or Blackburst, though they don't map without some math. :)

[Fred Dwyer]

Just to note that some Video and audio separately recorded does sync. I have no idea why. My 3 Canon VIXIA cameras (HFG10, HFS20, HFM52) sync perfectly with my Marantz PMD660 over 1.5+ hour programs, of which I shoot 4 every year. Lip sync is maintained to the end.

[Ron Evans]

Then you are very lucky. Have you really looked at the timeline with a 1 frame scale and can say that all the waveforms line up exactly ? With consumer cameras it is very unusual to have the audio stay in sync with each other that long. With my cameras with video in sync, the audio can be off by a quarter of a frame to start. Unlike tape the AVCHD cameras do stay within the frame though so if you are not that critical it would be OK. With timeline scale at 1 sec you would not see the difference but would hear it as a reverb or echo. DV for instance only needs to be within 1/3 of a frame to meet spec. So syncing 2 DV cameras could be 1 2/3 frames out between each other.

Ron Evans