Wirecast sync problems

I'm wondering if others have had audio/video sync issues trying to broadcast H264 with wirecast. When broadcasting a live stream, multicast or automatic unicast to a QTSS server (for relaying) I observe the following behaviour...

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Wirecast(WC) or QuicktimeBroadcaster(QTB)

* Mpeg4 encoding audio/video sync is fine (but video quality ordinary)

* QTB/H264 better video quality and sync stays solid & plays with VLC

* WC/H264 better video quality but video delayed w/r/t audio from a few frames to 1/2 to 1 second depending on source material

* Using beta elgato turbo264 component reduces processor load (WC) but sync problems still remain. (Beta turbo264 & QTB not compatible)

*** All the above encoded to 480x270(16:9) image/mpeg4 audio at 1.5Mbps total data rate

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In wirecast(WC) I used three sources...

(a) 4:3 dv pal video file at full screen resolution

(b) 16:9 mp4 (h264) video file at 480x270

either live video or playing back videotape through firewire input.

The camera source (c) played back at something close to sync, but still with the

picture lagging the video by a few frames. Both the video files dropped sync to something about one half to one full second.

Note this... If I used WC to switch between camera source and the video files, the delay was repeatable, so it would return to the small delay with the camera, and then stretched out to the large delay with the video files (encoding issue?)

I was using h264 packetiser settings, and a 1400 byte rtp payload for the audio.

I also noted that it was very, very difficult to get a reliable playback from vlc - the 1400 rtp payload setting on the mpeg4 audio seemed to work, but any other settings resulted in vlc crashing.

So to compare, I then quit WC and recreated as far as possible the same

network, audio and video codec settings using Quicktime Broadcaster.

The resultant broadcast from QTB (I could only use the live camera feed, but

i was able to use the internal tape playback to make it easy to check for

sync issues) stayed in sync, and also played in sync with vlc player, and was

stable.

The network settings were automatic announce to a QTSS. It is also just H264 encoding in wirecast that is the issue - MPEG4 does not suffer from the sync issues.

Short of creating another partition on my laptop, and installing wirecast

again without any other 3rd party software/codecs, I'm not sure where to go...

( i have ffmpeg libraries installed as a result of using Visual hub - but in theory I would think that QTB would have been affected too if that was the case...)

It does seem to be a quirk of the process that wirecast is using to encode the

H264 files, as QTB does not exhibit the same behaviour. Also the repeatable nature of the different delay times switching sources within wirecast suggests to me it is tied up with encoding.

Have others noticed the same issue?

John blyth

Wirecast sync problems - H264