usecase where I was able to demux audio from video and mux with modified audio and render it in Browser

Hi,
I started working on NaCl recently and I was successful in applying few
post-processing effects to the audio and playing back onto the Chrome
browser.

Now, my requirement is to demux the audio from the video which is played
using HTML5 <video> tag and apply the effects to the audio and remux it
back and render it in the browser. I realized FFMPEG would help me to demux
and remux the raw video stream. And also I read somewhere that it has VA
API (Video Acceleration) that helps to render the remuxed video onto the
screen. I am little bit confused on this and looking to start on this
concept.

Here are my clear thoughts what I want.

   - Able to demux audio from video and remux by applying few effects to
   the audio stream, may be ffmpeg so I need one sample where I could do this.
   - If so how can I apply this step to the video that is played using
   HTML5 <video> tag. Is it possible if not do I have to start writing my own
   HTML5 video player.
   - How can I render the remuxed video and audio without any lags.

Any help is highly appreciable.

Is GStreamer can be another bet for me?

Thanks alot for your help.

Best regards

symadept