[Libav-user] video(webm) muxed using libavformat gets blurred after few seconds and gets resized

ravikiran.bs ravikiran.bs at zohocorp.com
Wed Feb 28 15:46:07 EET 2018


I have two questions for two different cases here. I am trying to mux vp8 video stream and opus audio stream into a webm file using libavformat. I am receiving these as RTP streams on my server where I generate the muxed webm file. 

CASE 1 :

I am muxing to a video only webm file, by adding only vp8 stream. In this, I am getting the file successfully. But, when I play the file I find that for initial 3-4 seconds the video is visible and fine (though it blurs very slightly but its visible and manageable). But, after that the video suddenly blurs out completely and we can't see the image at all. Why this sudden blur after 3-4 seconds ? 

Also, after 3-4 seconds the video suddenly resizes when I play it in vlc. Why this resize is happening ? There was no resize of video from the source. 

You can find the output sample file for case 1 here : 


CASE 2 :

I am muxing both audio(opus) and video(vp8) streams into the webm file. Here, when I use a wired mic or earphone on the source side the audio is audible, otherwise the noise in the audio is so much that we can't hear the voice.  Why so much noise is getting added, when the audio is already opus encoded from chrome browser ?

And, here as I am muxing both opus audio and vp8 video, I can't see the video at all when I play it in vlc. There is complete blur right from the begining. Why is this happening only when I mux both the streams?

You can find the output sample file for case 2 here : 


I am using av_interleaved_write_frame() method to write the packets into the file. Please help me out in this. Thank you.


Ravi Kiran B S


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