Transcoding NellyMoser to AAC

[Jonathan_Daily]

I am streaming live music performances from the web using Flash ActionScript to Wowza 4. Downstream, we are using both RTMP and HLS streams. Since we are streaming music we are using the NellyMoser codec because Speex does not provide us with the same audio quality. The HLS stream requires the audio to be encoded as AAC in order for it to work. Unfortunately NellyMoser cannot be transcoded to AAC using the Wowza Transcoder addon because NellyMoser is proprietary.

The requirements are:

• streaming from the web using flash

• audio and video available on all devices downstream

• high quality audio w/ minimal compression for live music

I have heard that FFMpeg may be able to do the job.

Is there anyone who can help me implement a solution for this?

Thank you!

[Paul_Shields]

Hi,

If Speex is not acceptable to you then yes you could look at transcoding the audio from NellyMoser to AAC. A typical ffmpeg command to do that would be something like this:

ffmpeg -re -i http://[source-stream] -vcodec libx264 (or copy if h264)  -acodec aac -ab 128000 -ar 48000 -ac 2 -strict -2 -f mpegts udp://[WOWZA-SERVER-IP]:10000

Or if processing static files for later re-streaming, it may be a somewhat simpler:

ffmpeg -i yourinput.flv -vn -acodec libfaac output.mp4

or more advanced, including pushing output to Wowza as an mpegts stream:

ffmpeg -re -i "%WMSAPP_HOME%/content/sample.mp4"  -vcodec libx264  -vb 150000 -g 60 -vprofile baseline -level 2.1 -acodec aac -ab 64000 -ar 48000 -ac 2 -vbsf h264_mp4toannexb -strict experimental -f mpegts udp://127.0.0.1:10000?pkt_size=1316

These are untested examples, but it may give you some ideas to play with. Depends on the source really. Are you looking at transcoding the live stream or processing recordings after the event?

If streaming and transcoding in realtime then it would certainly be simpler to go with Speex audio and let the Wowza Transcoder do the work.

We have a couple of VLC and ffmpeg example articles which may also help.

Paul

[Roman_Shmelev]

Hi, I was previously transcoding nellymoser and can make wowza module for you or consult regarding any related questions, you can write me to roman@dynamicstreaming.net

[Paul_Shields]

Hi,

You may also find the following article of interest. It explains how to set up a Flash application that can push H.264 and Speex audio into the Wowza Transcoder. This will generate a playable MP4 output with compatible video and audio. It does require the Transcoder AddOn, but removes any intermediate processing.

Paul