On 2010-11-16 09:44, Irfan Shaikh wrote: > Hello All, > > I have been facing dificulty in using snd_pcm_mmap_begin and snd_pcm_mmap_commit. > Shows Seg fault as pointed by comment in code below. > Please tell me what wrong i am doing and how do i correct. > > /###################################################################################/ > unsigned int count = (alsaParams->frames/(((alsaParams->bit_per_sample)*(alsaParams->num_channel)) / 8)); > unsigned char *data = alsaParams->data;https://owa.sasken.com/owa/?ae=Item&t=IPM.Note&a=New# > snd_pcm_sframes_t frames_available, frames_transmit; > const snd_pcm_channel_area_t *area; > snd_pcm_uframes_t offset; > char *outbuffer; > int result; > > /*available space in audio-buffer to write to*/ > frames_available = snd_pcm_avail_update(alsaParams->pcm_handle); > > /* > * prepare the areas > * and get back area, offset and frames_transmit > * frames_transmit gives back the REAL value of available frames which could be written to in the mmaped-area > * frames_transmit are less than frames_available > */ > frames_transmit = frames_available; > > snd_pcm_mmap_begin(alsaParams->pcm_handle,&area,&offset,&frames_transmit); > > /*calculates the mmaped-buffer which could be written to*/ > outbuffer = ((char *) area->addr + (area->first + area->step * offset)/ 8); // ****** SEGFAULT ******* Well, the only pointer dereference is to area, so area has an invalid pointer. Please check the return value of snd_pcm_mmap_begin to see why. > > /*gives back the virtually written (writable) frames which should be always == frames_transmit*/ > result = snd_pcm_mmap_commit(alsaParams->pcm_handle, offset, frames_transmit); > > memcpy(outbuffer, data, count); //data is actual data Hmm, I've haven't used snd_pcm_mmap_* in a long time, but shouldn't the memcpy be above snd_pcm_mmap_commit? Second, if you're using memcpy, why don't settle with snd_pcm_writei in the first place? -- David Henningsson, Canonical Ltd. http://launchpad.net/~diwic _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
