Problem of audio / video sync when recording

[Debo_Sotnas]

Hello,

I have WowzaServer Developer Edition installed on a linux server. My project is to record and automatically post the video on YouTube. (Using the YouTube API).

Using the application "Recording " which brings Wowza (the sample application as an example), record and save a file. FLV without problem.

When playing or downloading this file you can see the recorded video correctly (no synchronization problem.) But to post it on youtube to upload api or “manually” to YouTube, the sync problem occurs between audio and video.

At first I thought the time was constant sync. Then I saw it was a problem that occurred when there was a silence at the time of recording (in user pc).

For this to make “setSilenceLevel = 0” had been solved. Despite this, on Mac and some PC is still giving this problem.

The strange thing is that when downloading the video recorded on any machine, is displayed with correct timing.

I tried many things. Reformat the record. Search sync time average and corrected through ffmpeg. Set in Application.xml times to sync. Other tries.

This can be corrected?

if some of the codecs of the client, how to unify and / or correct this?

can independently record audio and video (and then join with ffmpeg)?

[Richard_Lanham]

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, which is not likely to change any time soon if ever. You might be able to use ffmpeg or other encoder to re-encode.

Richard

[Charlie_Good]

No, it will not be possible.

Charlie

[Charlie_Good]

No, it will not be possible.

Charlie

[Richard_Lanham]

Try ffmpeg. For example this will make slice of the first 10 minutes:

ffmpeg -y -i whole.mp4 -acodec copy -vcodec copy -ss 00:00:00 -t 00:10:00 slice.mp4

There is link to pre-built ffmpeg in this article:

https://www.wowza.com/docs/how-to-use-ffmpeg-with-wowza-media-server-mpeg-ts)

Richard

[Richard_Lanham]

I think there is a way to correct that in ffmpeg, this looks like a useful howto:

http://www.kkoncepts.net/node/69

I’m not sure if the result will still be key frame aligned. You can also try MS Expression 4 encoder:

https://www.wowza.com/docs/how-to-encode-video-on-demand-content

Also, keep in mind, Wowza recordings might not work for purposes other than vod streaming from Wowza. They are necessarily compressed versions of your stream, whereas ideal mezzanine versions are normally recorded locally without compression.

Richard

[Richard_Lanham]

1. Not that I know of

2. Possibly, but not sure

Richard

[Richard_Lanham]

1. Not that I know of

2. Possibly, but not sure

Richard

[Vaclav_Flasar]

My recording of live stream from Wowza works fine. I record multiple key-aligned streams. Synchronization of recorded files as VOD works well too. I need to cut portion of the files. You recommended to reencode the recorded stream for this purpose. Is there a way how to reencode without to lose the key alignment of the files? Thank you.

[Vaclav_Flasar]

I’m using FFMPEG. I use FMLE and h.264/AAC(plugin) coding. The problem is that the input mp4 file plays ok. The FFMPEG output file has audio time-shifted. Each time is the shift different. I tried to turn on and off the option “start on keyframe” in LiveStreamRecord, no difference. Do you have any idea what could be the culprit? The MOOV atom is placed at the end of the file in wowza as well as in ffmpeg AFAIK…

[Vaclav_Flasar]

Richard,

Thank you for your time and help! Unfortunatelly it still does not work :-(.

1. Is there any other way how to record the origin stream similar to LiveStreamRecord that allows programmatically control the start and finish of the recording?

2. Will Wowza 3 with the DVR function possibly address this problem with compatibility of the recorded stream?

Thank you!

[Vaclav_Flasar]

OK, let’s say I will have somehow correctly recorded 3 streams of the originally adaptive live stream. These streams are not key alligned anymore (I needed to run tham through FFMPEG postproduction).

Question: Will it be possible to do adaptive streaming on non-keyalligned files in final version of Wowza 3 server?

Thank you Richard for your time and advice!