Live Stream Recording Audio and Video Sync Issue

[sal_jefferson]

A recording made from a live stream in Wowza should playback from a Wowza vod application, but might not work well or at all for other purposes. It often has to do with the fact that Wowza places the moov atom at the end of the file rather than the beginning.

Please test the recording with one of the example players that ship with Wowza. If playback is correct in the sample player, then you can try re-encoding the recording with ffmpeg and see if that fixes the recording in your custom player.

Also, try different settings in the encoder. Other users have found that changing to 24fps video fixed audio sync issue. I don’t think that is a fix-all in other situations necessarily, but changing audio and video details is where I would start.

If all else fails you can open a ticket with support. To do so please follow this guide and send required information to support@wowza.com:

How to create a compressed zip file in Windows, OS X, and Linux

Regards,

Salvadore

[sal_jefferson]

Sdabhi, where you requested to send a sample recording with a/v sync issues to support for testing? If you have not sent a sample, and your ticket is still open, please do so support can get a better understanding.

Salvadore

[Diogo_Moraes]

I was having this problem as well when recording with mp4. For me the problem was the variable frame rate on video. So I changed to FLV recording, and when I finish de recording, I use ffmpeg on it to convert to mp4. No more problems on audio sync since then.

[Michelle_B]

Hi,

@sdabhi: There was a fix in the recent Wowza versions that fixed this issue. Do make sure that your Wowza server is updated to the latest version available and test again. Do make sure that you have rollback procedures in place and that you test thoroughly.

@noface0711: what Wowza version are you using?

Michelle

[Andrew_Ramberg]

Hello,

Are you playing the recorded file through Wowza as a VOD asset or as a progressive download mp4? The recordings done with Wowza Streaming Engine do not support direct playback via progressive download.

Regards,

Andrew

[Andrew_Ramberg]

Hello,

When Wowza Streaming Engine records files it places a moov atom at the end of the recording. Since it’s created from a live stream, the end time has not been determined until the recording stops. This is fine when the files are played back as a VOD asset from Wowza Streaming Engine but could be the reason why your downloaded and post-Wowza encoded files are showing incorrect time information. For some types of playback such as progressive download, the moov atom should be placed at the beginning of the recording. This can be done external to Wowza using a program such as ffmpeg, with the -movflags faststart switch, which will re-position the moov atom to the beginning of the file and hopefully resolve this issue.

Best regards,

Andrew

[Andrew_Ramberg]

Hi pcurley,

Please open a new support ticket referencing this forum post. Our Engineering Team has identified an issue with some live-record recordings being out of lip sync and has a fix available that will be included with our next update. We would like to see if your situation matches this current known scenario or is a different problem.

If you could include a zipped copy of your conf/ and logs/ directories with this ticket, that will help us determine if this is a relevant fix.

Best regards,

Andrew

[Andrew_Ramberg]

Hello,

As to the live-record sync issue, we adjusted the codec config timecodes to match first packet in list and fixed timecode of first data packet to match trimmed audio/video. Given that it’s a timing issue fixed with live-record, it is difficult to say which encoders would have shown this issue repeatedly. A new public release of Wowza Streaming Engine is coming soon that will also include this fix.

Best regards,

Andrew

[Richard_Franklin]

I’m having the exact same problem described by sdabhi. Live stream is perfect, while recorded MP4 has A/V sync issues.

[philip_curley]

Hi Michelle, I am also experiencing similar A/V sync issues with mp4 recording.

We’ve been researching using Wowza as a recording alternative to our sometimes unreliable CDN live recording. After some initial testing we are discovering cases when Wowza is out of sync but the CDN recording is in A/V sync! Any insights to why Wowza recording unsyncs?

Our Wowza version is 4.4.0 (build 17748).

[philip_curley]

Andrew,

We are downloading recordings and we encode them for VOD delivery on a variety of different players, JWPlayer for example. Just to be clear, I am taking about the recorded files before we send them to encoding.

I have discovered a difference between the Wowza and CDN recordings. On both recordings or video stream is shorter duration than the audio stream. However, the Wowza MP4 recorded stream does not have the correct stream “start_time” value to align the A/V streams.

In fact, ALL of our Wowza recordings have a video start_time parameter of “0.06600” regardless of the A/V stream durations. Is this a bug or is it normal behavior for the recording feature?

Some info on our recording parameters:

• Version existing file

• Record Data

• Start on Keyframe

• Segmentation Option: none

[philip_curley]

hi Andrew,

Thanks for your response, I am sorry I missed it. I am excited to upgrade my Wowza to 4.5.0 because I am assuming the fix you reference is in this release.

I have generally found that my clients who have recording issues are using Wirecast and usually a stream capture devices like a Black Magic box. My suspicion is that the issue caused by poor handling of framerates from the camera to the encoder (such as capturing at 59.94 but encoding at 30 fps).

If I have further issues with 4.5.0 recorder, I will let Wowza know.