Stefano D'Angelo wrote: > The problem is quite simple: this USB card does not support DMA transfers No USB device supports DMA transfers. USB devices support USB transfers. The host controller supports DMA transfers. Yours does, too. > Takashi told me to use an intermediate buffer, This is just because the buffer for a USB frame must be continguous, but you cannot always guarantee this when you're near the end of ALSA's ring buffer. > but I really don't know how to do it. Should I copy data from the > buffer (playback) on usb transfer completition callbacks? You should copy the data just before you submit the URB. In other words, yes. > But in such case isn't it the same to just copy data into the urb's > transfer buffer? This is indeed the same. The URB's transfer buffer _is_ the intermediate buffer mentioned by Takashi. The opposite, i.e., not using an intermediate buffer, would mean that the URB's transfer_buffer pointed into ALSA's ring buffer. > I tried to avoid using this buffer and what I obtain is something that > resembles what the card should be playing but with huge noise. How do you determine how much data to send in each USB frame? Regards, Clemens ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-devel
