[Live-devel] Transcoder Question

[Ross Finlayson]

>I am trying to develop an audio transcoder using the live.com streaming
>media library.  The goal is to receive L16 RTP audio streams and transcode
>them on the fly to PCMU audio, then forward the new streams to a different
>multicast address.  I found the uLawFromPCMAudioSource that already exists
>in the library and tried to use that filter for the transformation.

Susanne,

I didn't have time to look at your code in detail, but one thing you should 
note is that in the "audio/L16" RTP payload format (a 16-bit PCM RTP 
stream), audio samples are sent in *network byte order* - i.e., big endian.

Therefore, when you create the "uLawFromPCMAudioSource" filter that you'll 
feed this incoming PCM data into, you should set the "byteOrdering" 
parameter to 2, to indicate that the input data is in big-endian order.

>Also, I am planning on adding down-sample code so I can transform
>L16 - 16kHz -> PCMU - 8KHz.  Would a new filter be the appropriate place
>for me to add that?

Yes, I think so,


	Ross Finlayson
	LIVE.COM
	<http://www.live.com/>