I recently ran into an audio/video sync problem while recording continuous two hour+ videos in the AVCHD format and rendering the files to the mp-4 format for upload to Vimeo. I reproduced the exact same out of sync condition with two identical cameras, 3 computers, multiple render formats and different file importation methods. This is ntsc 29.97 video from Cannon M-500 camcorders and I'm using V12 Pro.
The camera breaks the recording into multiple files every 1.9 GB (11:20). I surmised the out of sync must be related to the re-assembly because if each individual file is rendered separately the sync is fine. It's only when I try to render one continuous 2:00+ file that things go wrong. Here's what I discovered and if someone can explain this to me I'm all ears.
Importing the files directly from the card or coping them to the hard drive first made no difference. Cannon's file import utility copied the individual files exactly the same as Windows Explorer did. Be it from a file copied to the hard drive or directly from the card, if the individual files were assembled into one file using the Vegas Device Explorer the resulting file was a different length than if the individual files were imported and butted together on the time-line And here's the rub: neither the single unbroken file created by device explorer or the butted together files maintained A/V sync when rendered. Files imported with TSmuxer were of yet another length and still out of sync. Things start in sync and get progressively worse. Lips are noticeably out of sync by about the 40 minute point and laughable at 2 hours in the rendered version.
I set a camera up to record a running stopwatch and at the end talked to the camera so I could check both the actual time and lip sync. I repeated this test twice and the two importation methods (Device Explorer & Individual) produced the exact same results each time. The two hour marks on the stop watch occurred at different points and neither matched the two hour point on the time line.
Using the 2 hour mark on the Vegas time-line as a reference point the Device Explorer import produced a file that was 8 frames short of 2 hours. The 11 butted together files were 28 frames short of the 2 hour mark.
The maddening part of this is that whether I used the Device Explorer import or the Individual File import method the sync was perfect for either one when viewed in the Vegas preview window while editing. The out of sync occurs only when the file is rendered. It rendered out of sync files in mp-4 using Sony AVC, MC and TMPGEnc VMW5. It was also out of sync in mpeg-2, AVI and MXF formats. The Device Explorer file, which came closest to matching the Vegas 2 hour time line mark is the most out of sync when rendered.
Through trial and error I found if each individual clip's AUDIO file was cross-faded one frame into the preceding clip the rendered file was perfect from start to finish. This resulted in an audio file that was 38 frames shorter than the 2 hour mark on the time-line The audio cross-fades were indistinguishable in the final rendered file.
Here's the file info: AVCHD format at 22.7 Mbps 1920 x 1080, 29.97 AVC (High@L4.0) (CABAC / 2 RefFrames). Audio 256 Kbps, 48.0 Khz, 16 bits, 2 channels, AC-3. In other words, the standard
Canon MXP 24 Mbps High Quality mode.
Is this something unique to these cameras? Is the audio off, is the video off, is the time line off? I don't care where the actual two hour mark really is as long as the lips announcing it agree with the ears.
The camera breaks the recording into multiple files every 1.9 GB (11:20). I surmised the out of sync must be related to the re-assembly because if each individual file is rendered separately the sync is fine. It's only when I try to render one continuous 2:00+ file that things go wrong. Here's what I discovered and if someone can explain this to me I'm all ears.
Importing the files directly from the card or coping them to the hard drive first made no difference. Cannon's file import utility copied the individual files exactly the same as Windows Explorer did. Be it from a file copied to the hard drive or directly from the card, if the individual files were assembled into one file using the Vegas Device Explorer the resulting file was a different length than if the individual files were imported and butted together on the time-line And here's the rub: neither the single unbroken file created by device explorer or the butted together files maintained A/V sync when rendered. Files imported with TSmuxer were of yet another length and still out of sync. Things start in sync and get progressively worse. Lips are noticeably out of sync by about the 40 minute point and laughable at 2 hours in the rendered version.
I set a camera up to record a running stopwatch and at the end talked to the camera so I could check both the actual time and lip sync. I repeated this test twice and the two importation methods (Device Explorer & Individual) produced the exact same results each time. The two hour marks on the stop watch occurred at different points and neither matched the two hour point on the time line.
Using the 2 hour mark on the Vegas time-line as a reference point the Device Explorer import produced a file that was 8 frames short of 2 hours. The 11 butted together files were 28 frames short of the 2 hour mark.
The maddening part of this is that whether I used the Device Explorer import or the Individual File import method the sync was perfect for either one when viewed in the Vegas preview window while editing. The out of sync occurs only when the file is rendered. It rendered out of sync files in mp-4 using Sony AVC, MC and TMPGEnc VMW5. It was also out of sync in mpeg-2, AVI and MXF formats. The Device Explorer file, which came closest to matching the Vegas 2 hour time line mark is the most out of sync when rendered.
Through trial and error I found if each individual clip's AUDIO file was cross-faded one frame into the preceding clip the rendered file was perfect from start to finish. This resulted in an audio file that was 38 frames shorter than the 2 hour mark on the time-line The audio cross-fades were indistinguishable in the final rendered file.
Here's the file info: AVCHD format at 22.7 Mbps 1920 x 1080, 29.97 AVC (High@L4.0) (CABAC / 2 RefFrames). Audio 256 Kbps, 48.0 Khz, 16 bits, 2 channels, AC-3. In other words, the standard
Canon MXP 24 Mbps High Quality mode.
Is this something unique to these cameras? Is the audio off, is the video off, is the time line off? I don't care where the actual two hour mark really is as long as the lips announcing it agree with the ears.