Experiencing Latency with audio playing

robbiesullivan · Post by **robbiesullivan** » Sun Dec 04, 2005 7:18 pm

Hello,
I've got vxml app pretty much functional now, and I am just begining to fine tune it. I've been noticing the huge latency when my audio files play and I was wondering what steps I can go about to improve it.

The struture of the application is to retrieve .wav files (anywhere from 160kbs to 1.5 mbs) over HTTP and play them. The application is hosted on an hosted IIS server.

two things:
1. when I inistally call, I find the first opening .wav file takes a while to to play, maybe a half a second which is a lot (the file itself is 160kbs).
2. Later on in the vxml a request is made to play the main content which can be anywhere from (160kbs to 1.5mbs). This can take 2-4 seconds to start playing.

Is there anyway I can start queing up these audio files in the background?

Any tips would be greatly appriciated.
thanks

adriannaude · Post by **adriannaude** » Mon Dec 05, 2005 11:17 am

If you set the fetchhint attribute of the audio tag to prefetch then the audio files are loaded when the vxml is loaded rather than when the audio tag is executed. That might help....

Adrian

robbiesullivan · Post by **robbiesullivan** » Mon Dec 05, 2005 3:59 pm

will this work with dynamic audio files as well (audio files that are played with the EXPR attrbitue)?

I will try this with my non-dymanic files.

adriannaude · Post by **adriannaude** » Mon Dec 05, 2005 4:15 pm

I doubt that it would work with dynamic VXML because the interpreter doesn’t know the page until you actually generate the VXML, which I guess is mid-conversation. Another option is to try and host the voice files as close as you can physically to the voice platform so that the real network latency is minimised, or break the voice files into "sentences" so as to reduce their size (and therefore load time). My own feeling is that it is easier to bear a short delay between sentences rather than a huge delay between paragraphs.

robbiesullivan · Post by **robbiesullivan** » Tue Dec 06, 2005 7:54 pm

the vxml is not dynamic itself. Its static. I play some of the audio files via the <audio expre="" /> tag, so that I can dynimiclly play audio files. What I'm wondering is how to preload these <audio expr="" /> files.

thx for all the input.
Rob