FFMPEG causes certain MP4's to be out of sync

[jjones3535a]

Hi,

I have been able to successfully encode MP4 files to other video formats using FFMPEG for quite some time. Sometimes, however, there are certain MP4 files that play fine in Quicktime - but once converted with FFMPEG the audio is slightly out of sync. The audio sync issue is constant throughout the video.

It seems the MP4 files that are H.264 work fine with FFMPEG, but the MP4 files with MPEG-4 seem to have the audio sync issue.

Any solutions to this?

Thanks

[Soopafresh]

Try a different version of FFmpeg. Things change as they update, you might have a version that's problematic for that type of conversion.

BTW, are you changing the audio sampling rate? That could mess with the sync as well.

[jjones3535a]

Thanks for the response.

I'm actually using WinFF. I've tried 3 different versions, each with different FFMPEG versions released over the past year, and the audio sync issue remains within each.

I'm not modifying the sample rate. Here's WinFF's FFMPEG command:
"C:\Program Files\WinFF\ffmpeg.exe" -i "C:\sample.mp4" -vcodec wmv2 -acodec wmav2 -b 1000kb "C:\\sample.wmv"


Also, here are the details on the MP4 file that is out of sync. Per Gspot:

Video:
Codec: mp4v
Name: MPEG-4 Video
Frames/s: 29.963
320x240

Audio:
Codec: mp4a: MPEG-4 AAC LC
48000Hz 160 kb/s tot, stereo (2/0)

Any ideas on how to get FFMPEG to encode this file without audio sync issues would be greatly appreciated:

Thanks.

[jjones3535a]

Here's some detailed info on the file causing the sync issue as reported by MediaInfo. Could it be the Variable Bit Rate audio that is causing sync issues upon conversion? Thanks for the help.

Video
Format                           : MPEG-4 Visual
Format profile                   : Simple@L1
Format settings, BVOP            : No
Format settings, QPel            : No
Format settings, GMC             : No warppoints
Format settings, Matrix          : Default
Codec ID                         : 20
Duration                         : 2mn 25s
Bit rate mode                    : Variable
Bit rate                         : 613 Kbps
Nominal bit rate                 : 752 Kbps
Maximum bit rate                 : 3 401 Kbps
Width                            : 320 pixels
Height                           : 240 pixels
Display aspect ratio             : 4/3
Frame rate mode                  : Variable
Frame rate                       : 29.970 fps
Minimum frame rate               : 29.963 fps
Maximum frame rate               : 29.981 fps
Resolution                       : 24 bits
Colorimetry                      : 4:2:0
Scan type                        : Progressive
Bits/(Pixel*Frame)               : 0.266
Stream size                      : 10.7 MiB (79%)
Writing library                  : Lavc52.0.0
Language                         : English
Encoded date                     : UTC 2009-01-02 18:25:43
Tagged date                      : UTC 2009-01-02 18:25:47

Audio
Format                           : AAC
Format/Info                      : Advanced Audio Codec
Format version                   : Version 4
Format profile                   : LC
Format settings, SBR             : No
Codec ID                         : 40
Duration                         : 2mn 19s
Bit rate mode                    : Variable
Bit rate                         : 160 Kbps
Maximum bit rate                 : 219 Kbps
Channel(s)                       : 2 channels
Channel positions                : L R
Sampling rate                    : 48.0 KHz
Resolution                       : 16 bits
Stream size                      : 2.67 MiB (20%)
Encoded date                     : UTC 2009-01-02 18:25:43
Tagged date                      : UTC 2009-01-02 18:25:47

[Baldrick]

I guess it's the Variable FRAME RATE mode that causes the sync problem. Variable bitrate should work fine to convert using ffmpeg. Maybe try something like Variable Framerate Rx to convert to constant frame rate.

[jjones3535a]

Thanks for the suggestion - but unfortunately I can only use FFMPEG or some other batch utility.

[swiftor]

I have the same issues as well I believe. When I try to convert my f4v file to avi using WinFF, the audio is out of sync. Any solutions would be fantastic!