At Wed, 11 Oct 2006 16:19:44 +0100, James Courtier-Dutton wrote: > > Takashi Iwai wrote: > > At Wed, 11 Oct 2006 16:00:54 +0100, > > James Courtier-Dutton wrote: > >> Assaf Hoffman wrote: > >>> Hi, > >>> Thanks again for clear answers. > >>> In case the HW strip the IEC958 frames, where the ALSA stack expect to > >>> find the various frame data fields such as perr, valid bit, audio > >>> sample, user data and channel status? Is there a data structure the HW > >>> should follow when DMAing the striped data to the DRAM buffer? > >>> What do you think of such acceleration? Does this saves a significant > >>> CPU time processing the ICE958 frames? > >>> Many thanks. > >>> P.S. > >>> I was looking into the ASLA stack and I could find > >>> SNDRV_PCM_FMTBIT_IEC958_SUBFRAME_XX only in snd_pcm_hardware structure > >>> initialization. I could not see where it is used to tell the ALSA to > >>> process the data as IEC958 frames. > >>> > >> A majority of sound cards strip the frame, and only put the audio > >> samples in the DMA buffer. The sound card then stores the valid bits, > >> non-audio bit, user data etc. in a separate register on the sound card. > >> > >> The processing of the IEC958 frames is done in alsa-lib. > >> ALSA has two parts, and kernel part, and a user space lib. > >> The kernel part does as little as possible, with the user space part > >> doing all the format conversion etc. > >> > >> I have not looked closely, but I don't know if the alsa-lib decodes the > >> IEC958 frames or not yet. > > > > It can. iec958 plugin does encode/decode IEC958 frames. > > > > > > Takashi > > Does it let the user app set the valid, non-audio etc. bits? Yes, it takes arguments. Takashi ------------------------------------------------------------------------- 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
