[Live-devel] Audio Sync Issue from Axis Camera

[Justin Miller]

Apologies, yes we are using OpenRTSP, we can get synced audio and video
from VLC but the image quality is not very good. If we open the stream
directly in quicktime the audio and video are synced as well. The problem
is OpenRTSP is giving  inconsistent results, sometimes it's 5 frames out of
sync other times 2 or 3 and sometimes not at all. We found using the -y
modifier produces an issue with drifting audio, where it might be dead on
at the beginning but after 20 minutes is a full second out of sync. We also
found that if a file is 5 frames out of sync and we re-encode it with
ffmpeg it then produces a file that is less out of since with perhaps 2 or
3 frames. It is a very strange issue. The file seems to play better in VLC
and windows media player, meaning that only the videos that are up to 5
frames out of sync are noticeable. However in quicktime or Final Cut Pro
(basically anything based on quicktime) shows the issue to a much greater
degree. The stream is automatically encoded h.264 and aac audio. I do get
better results when I change the GOV settings to 8 and the bit rate to 6400
than any other setting on the camera. I am not sure why this is, I also get
better results when the camera is set to 24 fps and I set OpenRTSP to 23.95
fps also not sure why that is, again it is inconsistent though.

Thanks,

Justin M. Miller
Multimedia Specialist
Media Commons Project Manager
212A Rider bld.
University Park, PA 16802
814-863-7764
http://mediacommons.psu.edu


On Thu, Dec 15, 2011 at 8:31 PM, Ross Finlayson <finlayson at live555.com>wrote:

> We are trying to use an Axis Q6034 Camera that sends out a video and audio
> stream in h.264 and acc. The problem we are having is that the audio and
> video do not sync no  matter what we try.
>
>
> Is this a general problem with audio and video from this camera being out
> of sync, or just a problem with audio/video sync if you try to record it to
> a file using "openRTSP"?  (You didn't mention "openRTSP" in your message!)
>
> I.e., if you view the stream directly using VLC (i.e, not from a file),
> then is the audio and video in sync?  If not, then there's probably nothing
> we can do.
>
> If, however, you're seeing a/v sync problems only when you try to record
> the stream to a '.mov' or '.mp4' file using "openRTSP", then the problem is
> basically that the '.mov' and '.mp4' formats are ill-suited for recording
> incoming audio/video streams, and "openRTSP" is trying to do the best that
> it can.  To have any hope for this to work, however, you must give
> "openRTSP" an accurate 'frame rate' parameter (using "-f").
>
> Ross Finlayson
> Live Networks, Inc.
> http://www.live555.com/
>
>
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> live-devel mailing list
> live-devel at lists.live555.com
> http://lists.live555.com/mailman/listinfo/live-devel
>
>
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