MPEG-2 Audio Sync
 

Hello fellow Nano users would someone be able to test the Nano recording MPG @ 6-7 Mbps for audio sync. My MPG files are all about 40 frames out in lip sync. I am not sure if it's my system causing the problem or the Nano. If anyone can confirm I would really appreciate it.

Many thanks in advance.

Dear Lance,

We will be happy to test this in our lab on Monday.

What camera were your using?

Please describe your setup and menu options you used so we can try to duplicate it in our lab.

Hello Dan,
Thanks very much for that I have been working the NanoFlash hard for the last two days making MPG streams from my time line to burn DVD's. I edit and create the program on the time line in FCP and output via Blackmagic HD Extreme 3 with SDI to the NanoFlash to produce a MPG stream. DVD Studio Pro works with Elementary streams so I Demux with MEPG Streamclip to create a M2V and a AIFF file to import to DVD Studio Pro for mastering. I have traced the issue to the original MPG file from the Nano. Unfortunately I have to time to use the hardware to try to diagnose issues as I have to get my existing work out. I had a quick look for audio latency adjustment in SDI stream from the Blackmagic card and can not find any adjustments.

Hardware
Mac Pro 8 core
8 GBS Ram
Decklink Black Magic Extreme 3 with SDI I/O
Final Cut Pro 7.0.1

Many Thanks

Dear Lance,

Are you creating a SD DVD, or is the MPG file in HD?

Assuming that you are creating a SD DVD:

Could you connect a camera, setup for SD mode, output the SD-SDI to the nanoFlash, then record a test in MPG mode (SD)?

Then, in the nanoFlash, playback the MPG file to determine if the audio is in sync.

Hello Dan,
Yes the MPG file is for SD DVD creation.
I have connected the camera, and set the camera to SD mode, output for SD-SDI to the nanoFlash and have made a test recording in MPG mode (SD)?
I have noticed during recording on the NanoFlash intermittent audio on the NanoFash audio meters. During playback to my HD/SDI monitor the monitor reports loss of signal and as soon as the playback is stopped the SDI signal returns
The Blackmagic card output is set for SDI & HDMI & Y,R-Y,BY for video and audio output connections. The output processing is set for HD to HD and SD Anamorphic
I have attached the CF card to my Mac Book Pro which will playback mpg using Quicktime 7.6.4 and the play back from the CF card proves the lip sync is fine. The new editing system is a Mac Pro with Snow Leopard and Quicktime will not playback mpg, it’s pre installed with Quicktime 10.0.

I will have to try to isolate the problem to FCP, Declink or the OS.

Many thanks for your help Dan.

Dear Lance,

I am alerting our engineers to this thread.

We want to look at the issues you present.

Hello Dan,
I have at last been able to replicate the audio sync problem it is caused by the Mac Snow Leopard 10.6 and Quicktime X. If the same MPG clip is played on my Mac Book Pro with Quicktime 7.6.4 the vision and audio are in sync if the same clip is played back on the Mac Pro with Snow Leopard 10.6 running Quicktime X we then we have audio out of sync with vision, about 1.5 sec out of sync on MPG files.

The problem is if you create a DVD on Snow Leopard 10.6 hardware the errors are recoded to DVD if the files are all move in this case my MacBook Pro with Leopard 10.5 the DVD is created without lip sync errors.

The strange thing is that I have tried various quicktime files including the mov files from the CF cards and they all work fine, it appears to only effect the MPG files created by the NanoFlash.

Hi,

we are looking into this. Very peculiar.

Tommy

Hi Lance, after upgrading to Snow Leopard, I noticed MPEGStreamclip was doing some weird things so I actually replaced the codecs on my Snow Leopard system with the ones from Leopard. This fixed all the problems I was having but it's a hack for sure.

I'd rather see an official fix for this from somebody.

Hello Aaron,
Thanks very much for the info would it be possible to find out which files you moved to get MPEG Streamclip to work with Snow Leopard. I have to give away trying to use the Nano to make MPG files on this system, I have a lot of work on and I will get back to it after Christmas when things settle down a bit. I have found other issues with QuickTime X and Snow Leopard, how in the hell can Apple put out software with so many bugs and compatibility problems I will never Know. Apple in my opinion have a real creditability issue and they would do well to remember “Downward Compatibility” keeps everyone happy.

Hello Dan,
I just complete a recording of a few show in SD and the visual quality was fantastic. I have just ingested my vision from the compact flash cards to discover my audio is 6 seconds behind the vision. Well after a lot of thought and looking at the setup the only thing that I can see that may have caused this is the prerecord buffer. I remember when the buffer was activated in case I missed a cue that the time code on the NanoFlash advanced by 6 seconds prior to recording. When playing back SD clips on the NanoFlash the time code is not present.
Question:
What is the quickest way to deal with moving the audio and video to the correct point when you have such a lot of files to process and rework. I can do it manually on the timeline in FCP but it’s time consuming. I would appreciate any help, I have another show tomorrow and I will test the NanoFlash without the prerecord cache to confirm.

Many Thanks

Dear Lance,

One of the know issues with SD recording, with 1.1.150 is that the audio/video may be out of sync. However, we only expected a few frames out of sync.

Yes, I would turn off the Pre-Record Buffer for a test.

It is interesting to hear of the timecode jump by 6 seconds. We will check into this.

If you put your entire event on the timeline, then unlock the audio from the video, you may be able to adjust the audio/video sync in one operation. But this would depend on all of the files being off by the same amount.