USB complete book Isochronous transfer question

[jtboet]

Hello,

I would like some clarification about the topic of Isochronous data size in the USB book please. It says that the packet size per transaction can vary.
The book then gives an example about 44.1 kHz being 9 packets of 44 samples, then one packet of 45 samples.

I would like to know what happens at the PC end, Does the PC perform sample rate conversion / interpolation?
Can the packet size be one less also? say, 43 samples?
Is utilisation of this feature dependant upon specifying one of the synchronisation modes in the endpoint descriptor?

The reason i ask is because varying the packet size by one sample is causing me artefacts in the audio. I was hoping to use this as a method of synchronising the audio.

[Jan Axelson]

The host can use the data however it wants and might be expecting a particular packet size.

With that said, I'm not an expert on audio formats. The USB Audio 1.0 spec describes synchronization methods.

Jan